North Cumbria Sporadic Cryptosporidiosis Study - DWI,...

North CumbriaSporadic

CryptosporidiosisStudy

N o r t h C u m b r i a S p o r a d i c C r y p t o s p o r i d i o s i s S t u d y

Preface

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Preface

This Technical Report is designed as a detailed record for Steering GroupMembers and Researchers. As the study covered a protracted period of sixand half years, the aim of the Researchers was not only to ensure theconsistency and quality of the main epidemiological case control data butalso to monitor background factors and changes which may impingeupon the study. Data recorded may perhaps be useful for other researchersin the future.

This document includes a Section III, which contains a description of thetwo Local Authorities, with background information on the population,water supplies as well as aspects of animal husbandry. It also has a shortresume of the Foot and Mouth epidemic 2001-2002, as it affected thestudy area. Two succinct papers will be submitted for publication in peerreviewed scientific journals. The Executive Summary may be read as astand alone précis of the salient points and conclusions featured in thisReport.

Carlisle and DistrictPrimary Care Trust

Wavell Drive RosehillCarlisleCA1 2SETel: 01228 603608Fax:01228 603612www.northcumbriahealth.nhs.uk

N o r t h C u m b r i a S p o r a d i c C r y p t o s p o r i d i o s i s S t u d y 5

North Cumbria Sporadic Cryptosporidiosis Study

Allerdale and Copeland

1 March 1996 - 31 August 2002

Two collaborative studies led by North Cumbria Health Authority andThe Communicable Disease Surveillance Centre, London, workingtogether with the Local Authorities of Allerdale and Copeland,Carlisle Public Health Laboratory, West Cumberland HospitalMicrobiology Laboratory, Furness General Microbiology Laboratory,Cryptosporidium Reference Unit and the PHLS Statistics Unit.Contributions were also received from the Veterinary LaboratoriesAgency (Defra), United Utilities, Drinking Water Inspectorate,Department of Health, and United Kingdom Water Industry ResearchLimited (UKWIR).

IProspective case - control study into

sporadic cryptosporidiosis Allerdale and Copeland.

1 March 1996 to 29 February 2000.

IIIntervention Study - Comparison of incidence rates and risk factors

of sporadic cryptosporidiosis before and after the installation ofmembrane filters in the Ennerdale and Crummock water supply

zones.

1 March 1996 to 31 August 2002.

N o r t h C u m b r i a S p o r a d i c C r y p t o s p o r i d i o s i s S t u d y6

ContentsMaps 17

Acknowledgement 19

Funding 20

Membership of Steering Group 21

Key Points 25

Executive Summary and Conclusions 27

Section I - Epidemiological Study

1. Introduction 39

A Background 39

B Introduction 41

2. Aims 43

3. Methods 44

4. ResultsA. Annual Incidence in Allerdale and Copeland 48

(1 March 1996 - 31 August 2002)Comparisons with other Local Authorities, Districts and Nationally. 50

B. Case-Control Study 1 March 1996 - 29 February 2000i) Reported cases and controls: exclusions and exclusion reasons. 54

ii) Report from PHLS Statistics Unit - Descriptive Analysis, Single 61and Multivariable Analyses

C. Intervention Study 1 March 1996- 31 August 2002.i) Reported cases and controls: exclusions and exclusion reasons. 78

ii) Report from PHLS Statistics Unit. Comparative Analyses on 86Intervention Results.

D. i) Monitoring of media coverage 105

ii) Monitoring of time interval between date of reporting of case and 110interviews of cases and controls.

5. Discussions & ConclusionsA. Case Control Study 117

B. Intervention Study 125

6. References 130


Contents

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Section II - Microbiology

1. Local arrangements 136

2. Method 136

A Local laboratory methods B Reference laboratory methods for confirmation and genotype

3. Results 138

A Confirmation of laboratory isolatesB Genotype Results:

i) Case Control Study1 March 1996 - 29 February 2000ii) Intervention Study1 March 1996 - 29 February 20001 August 2000 - 31 August 2002

4. Discussion 139

5. Microbiology References 146

Section III - Background Information in Study Area1 March 1996 - 31 August 2002

1. Profile of Allerdale and Copeland Local Authorities 149

2. Water Supply in Allerdale and Copeland 1 March 1996 - 31 August 2002

A. Description of water supply zones, and water treatment works. 153

B. Description of District Meter Area (DMA) and changes in water supply arrangements. 162

C. Description of membrane filters. 168

D. Date of membrane filters commissioning 172

E. Monitoring of Cryptosporidium in Ennerdale and Cornhow water treatment works (WTW). 173

F. Microbiology tests used by Water Company for testing Cryptosporidiumat Ennerdale and Cornhow WTW. 187

G. Rainfall monitoring at Ennerdale and Cornhow WTW 188

H. Events and incidents reported to steering group. 205

I. Regulation of water supplies. 206


Contents

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3. Animal cryptosporidiosis - Allerdale and Copeland

A Animal census 209

B Veterinary Laboratories Agency - Animal isolates 212

C Examination of links between human cases and animal cryptosporidiosis. 218

D Foot and Mouth Outbreak chronology 221

4. Human cryptosporidiosis outbreaks 225

5. Chronology of Study 226

6. Section III References 229

Section IV - Appendices

1. Questionnaire 232

2. Information leaflet 242

3. Pictorial leaflet on liquid measurement 245

4. Letters to cases and controls 246

5. A. Letters to general practitioners 1996 248i) Enclosure : Summarised protocol 249ii) Enclosure : Questions and Answers Leaflet 1996/7 251

B. Further letters to General Practitioner 253

6. Press releases (2) 255

7. Interview protocol 258

8. Abbreviations 260


Contents

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Tables and Figures

Section I - Epidemiological Study

Table 1 Introduction : Number of cases:Incidence rate of cryptosporidiosis and ratio of salmonellosis to cryptosporidiosis. 41

Table 2 Results : Number of District reported cases of cryptosporidiosis for Allerdale and Copeland Local Authorities by month 1994 to 2002. 49

Table 3 Results : District reported cases of cryptosporidiosis by Local Authority in North Cumbria 1993 to 2002. Number/rates per 100,000. 51

Table 4 Results : Comparison of reported Cryptosporidium cases by study area, Health Authority and England and Wales 1996 to 2001. 52

Table 5 Results : United Kingdom Number and Incidence rates for Cryptosporidium Laboratory reports 1991 - 2000. 53

Table 6 Results : Sporadic case-control study: Summary of case exclusion reasons from 1 March 1996 to 29 February 2000. 55

Table 7 Results : Sporadic case-control study. Summary of case exclusion reasons 1 March 1996 to 29 February 2000 - Allerdale. 56

Table 8 Results : Sporadic case-control study. Summary of case exclusion reasons 1 March 1996 to 29 February 2000 - Copeland. 57

Table 9 Results : Sporadic case-control study : controls generated and usage. 59

Table 10 Results : Sporadic case-control study. Controls exclusion reasonsNumber in (%) contacted but not incorporated: Category A. 60

Sporadic Cryptosporidium in West Cumbria : A Case-control StudyStatistics Report by Neville Verlander (PHLS Statistics Unit)

Table 1 Age and water source. 63

Table 2 Age and sex distribution among the water sources. 63

Figure 1 Primary cases by water supply zone. 64

Table 3 Cryptosporidium infection rate per year per 100,000 by water source. 64


Contents

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Table 4 Yearly Distribution of Cryptosporidium infection by water source. 65

Table 5 Case Symptoms 65

Table 6 Age and sex distribution of hospitalised cases. 65

Table 7 Multivariable model - usual Total daily consumption of cold unboiled water -all data. 67

Table 8 Multivariable model - usual daily consumption of cold unboiled water at Home. 68

Table 9 Multivariable model - Total consumption of cold unboiled water excluding subjects served by mixed supplies. 69

Appendix A Single Variable Analysis - all data 70

Appendix B Single Variable Analysis - excluding mixed water supply 74

Table 11 Results : Cryptosporidiosis Intervention Study. 1 March 1996 to 31 August 2002. Comparison of case exclusion reasons for the pre and post Intervention periods of the study. 80

Table 12 Results : Cryptosporidiosis Intervention Study. Comparison of case exclusion reasons for the pre and post intervention periods of the study - Allerdale. 81

Table 13 Results : Cryptosporidiosis Intervention Study. Comparison of case exclusion reasons for the pre and post intervention periods of the study - Copeland. 82

Table 14 Results : Cryptosporidiosis Intervention Study. Comparison of control usage for defined periods of the study. 84

Table 15 Results : Cryptosporidiosis Intervention Study. Comparison of control exclusion reasons. Contacted but not incorporated category A. 85

Post-Installation Results 1996 - 2002 Report by Neville Verlander, Andre Charlett (PHLS Statistics Unit) and Mark Reacher (CDSC)

Table 1 Water sources, zones, filtration and populations served, Copeland and Allerdale Local Authorities 1996 - 2002 86


Contents

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Table 2 Time periods of observation by introduction of membrane filtration and the Foot and Mouth Disease Epidemic in Livestock. 88

Table 3 Age, sex and water source of all cases & controls 89

Table 4 Age and sex distribution all cases & controls 89

Table 5 Case symptoms 90

Table 6 Age and sex Hospitalised cases 90

Figure 1 Annual incidence rate per 100,000 91

Figure 2 Average number of primary cases from 1 March 1996 to 29 February 2000 (Pre intervention) 92

Figure 3 Average number of primary cases from 1 March 2000 to 31 August 2002 (Post intervention) 92

Figure 4 Incidence rate per 100,000 person - years and 95% CI 1 March 1996 - 29 February 2000 (Pre intervention) 93

Figure 5 Incidence rate per 100,000 person - years and 95% CI 1 March 2000 - 31 July 2000 (Commissioning membrane filtration) 93

Figure 6 Incidence rate per 100,000 person - years and 95% CI 1 August 2000 - 20 February 2001 (Established membrane filtration) 93

Figure 7 Incidence rate per 100,000 person - years and 95% CI 21 February 2001 - 20 February 2002 (Established membrane filtration and FMD epidemic) 94

Figure 8 Incidence rate per 100,000 person - years and 95% CI 21 January 2002 - 31 August 2002(Established membrane filtration post FMD epidemic controls) 94

Figure 9 Incidence rates per 100,000 person years before and after installation of membrane filters. 95

Table 7 Modelling of study data in Poisson Regression model (Models 1 and 2) 96

Table 8 Frequency of months with stated number of cases per month in each period. 99

Table 9 Adjusted odds Ratio (OR) and 95% Confidence Internal CI per pint of water in each period. 101


Contents

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Table 10 Model averaging over the five periods. 102

Appendix Incidence rates by water zones, and time period for primary cases 104

Media Interest Study (28 April to 30 November 1999) - A survey by Joy Williams (RA)

Figure 1 Interviewees’ knowledge of cryptosporidiosis prior to participating in the cryptosporidiosis case-control study. 108

Figure 2 Source of cryptosporidiosis Information of Interviewees who had heard of cryptosporidiosis prior to participating in the case-control study. 108

Table 1 Question 1 - Had you heard about cryptosporidiosis before being contacted. 109

Table 2 Question 2 - Can you remember where you heard about cryptosporidiosis. 109

Monitoring of time intervals between report date and interviews

Table 16 Sporadic case-control study: Time interval between reporting date and completion of primary case interview. 112

Table 17 Number of primary cases with reference to number of controls per case. 112

Table 18 Time interval between report of case and completion of interviews for case and corresponding set of 3 or more controls. 112

Table 19 Analysis of completion of interview times for primary cases and sets of controls. 1 March 1996 to 29 February 2000. 113

Table 20 Intervention study. Time interval between reporting date and interview of primary cases for defined periods of the study. 114

Table 21 Comparison of number of primary cases by number of associated controls in set for defined periods of the study. 114

Table 22 Comparison of time interval between report of case and completion of interviews for case and corresponding sets of 3 or more controls for defined periods of the study. 114

Table 23 Analysis of completion of interview times for primary cases and sets of controls 1 March 1996 to 31 August 2002. 115


Contents

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Section II - Microbiology

Table 1 Sporadic case-control study period 1 March 1996 to 29 February 2000. Cryptosporidium genotype by month from Cryptosporidium Reference Unit. 140

Table 2 1 March 1996 - 29 February 2000. Comparison age groups and genotype. 141

Table 3 1 March 1996 - 29 February 2000 Comparison case definitions and genotype 142

Table 4 Intervention Study Period 1 March 1996 - 31 August 2002 Cryptosporidium genotype by month. 143

Table 5 1 March 1996 - 31 August 2002 Comparison age groups and genotype. 144

Table 6 1 March 1996 - 31 August 2002 Comparison case definitions and genotype. 145

Section III - Background Information in Study Area 1 March 1996 - 31 August 2002

Table 1 Urban area population estimates in Allerdale and Copeland local authorities based on 2001 ONS Census data. 149

Table 2 Resident population by study age bands for each year of the study. 150

Figure 1 Profile of Allerdale and Copeland Local Authorities:Map of study area showing population density, based on Ward level indicators of sparsity and overlain with Water Supply Zone boundaries. 152

Table 3 Description of Water Supply Zones and Water Treatment Works (WTW):Allerdale Water Supply Zone Descriptions. 154

Table 4 Copeland Water Supply Zone Descriptions. 154

Figure 2 Map of Water Supply Zone Boundaries & Key Locations. 160

Table 5 Summary of Water Supply Zone and source details, treatment works descriptions and process details 1 March 1996 to 31 August 2002 161


Contents

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Table 6 WTW Closures and zones affected. 163

Table 7 WSZ number, names and details of “mixed” DMA’S. 163

Figure 3 Map showing mixed DMA Water Supply Zone Boundaries & Key Locations. 164

Table 8 Analysis of United Utilities WSZ Population figures, calculation of private and “mixed” supply populations and total population. 166

Table 9 Study Denominator Population Estimates 1996 to 2002. 167

Figure 4 Description of Membrane filters (A summary from information provided by United Utilities Plc):

Filter sub module with fibres exposed. 168

Figure 5 Assembled filter modules at Ennerdale. 169

Figure 6 Schematic of the CMF process at each WTW. 169

Figure 7 Micro strainer at Cornhow WTW 169

Figure 8 CMF “Skids” at Cornhow WTW. 169

Table 10 Monitoring of Cryptosporidium in Ennerdale and Cornhow WTW:Summary raw water monitoring (10 litre “grab” samples) at Cornhow WTW. 173

Table 11 Summary raw water monitoring (10 litre “grab” samples) at Ennerdale WTW. 173

Figure 9 Rainfall data: Rainfall at Cornhow water treatment works 1 March 1996 to 31 August 2002. 189

Figure 10 Rainfall at Ennerdale water treatment works 1 March 1996 to 31 August 2002. 197

Table 12 Animal cryptosporidiosis - Allerdale and Copeland:Summarised Defra Agricultural & Horticultural Census data: Small Area Statistics for Allerdale, Copeland and Cumbria (1996-2001). 210

Table 13 Animal Cryptosporidium Isolates reported by the Veterinary Laboratory Agency. 213


Contents

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Table 14 Cattle and sheep Cryptosporidium isolates for 1999. 215

Figure 11 Number of Cattle Cryptosporidium test & positive isolates by month for 1999. 216

Figure 12 Number of Sheep Cryptosporidium test & positive isolates by month for 1999. 217

Table 15 Examination of the links between human cryptosporidiosis and animal cryptosporidiosis. 219

Table 16 Examination of links between human cryptosporidiosis & animal cryptosporidiosis, summary for each year. 220


Map of Local Authorities, North Cumbria

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Map of Local Authorities, Allerdale & Copeland

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Acknowledgements

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Acknowledgements

We would like to thank the support and contribution of many colleagues: members of the SteeringGroup; staff at the local Authorities of Allerdale and Copeland; the Microbiology Departments ofWest Cumberland Hospital, Furness General Hospital, Carlisle Public Health Laboratory; TheCryptosporidium Reference Unit (CRU); Communicable Disease Surveillance Centre (CDSC);PHLS Statistics Unit; Veterinary Laboratories Agency (Defra); Drinking Water Inspectorate;Department of Health; United Kingdom Water Industry Limited (UKWIR); United Utilities; andNorth Cumbria Health Authority (now figure as Carlisle and District Primary Care Trust).

We are particularly grateful and thank, Mr Brian White and staff at Copeland Borough Council,who kindly provided an office base for the Research Worker in Whitehaven; this has facilitatedtravel to homes of cases and controls in West Cumbria.

The smooth progress and the production of accurate, reliable results in the Research involvedcollaborative efforts from many colleagues both locally and nationally. We are grateful to everyonewho contributed to this Research.

• Dr Margaret Knowles and staff at the Carlisle Health Laboratory; Dr Sarah Richards andstaff at West Cumberland Hospital Microbiology Laboratory and Dr Susan Partridge atFurness General Microbiology Laboratory, reported Cryptosporidium cases of residents ofAllerdale and Copeland to the Public Health Medicine Department, and sent isolates to theCRU.

• Dr David Casemore, Dr Rachel Chalmers, Dr. Kristin Elwin and Ms. Anne Thomas at theCryptosporidium Reference Unit (CRU) conducted tests to confirm and genotype theisolates.

• Ms Joy Graham, Ms Jennifer Clay and Mr Paul Blaylock ensured the prompt reports ofcases to the Research Assistant and also generated the controls for the research. Mr RichardLamb developed the programme for the generation of controls and also the administrativedatabase.

• The three Research Assistants: Mrs Emma Wigginton, Ms Joy Williams, Mr AnthonyPennington and their deputies: Ms Rachel Horton at Allerdale Borough Council, Ms MaryCosgrove and other deputies at Copeland Borough Council ensured not only thecontinuity but also the good response rate, the consistency and quality of the interviews.

• The Statisticians at PHLS Statistics Unit: Ms Claire Gilham, Mr Neville Verlander, MrAndre Charlett conducted the statistical analyses.

• The Consultants at the Communicable Disease Surveillance Centre: Dr. Patrick Wall, Dr.Ros Stanwell-Smith, and Dr. Mark Reacher provided epidemiological advice and shared thelead in this study.


Acknowledgements

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• Mr Keith Osborn and staff at United Utilities: Dr Charmian Kerr, Mr. MatthewWilkinson, Mr. Roy Dunbar, provided information on water supply zones, treatmentworks, Cryptosporidium and Giardia monitoring, membrane filters, and rainfall data; thesewere pertinent to the statistical analyses.

• Mr David Counter and Mr Andrew Holliman at the Veterinary Laboratories Agency(Defra) reported on animal cryptosporidiosis and the Foot and Mouth disease outbreak.

• Mr. Tony Lloyd, (Drinking Water Inspectorate) provided advice on the regulationspertaining to water supply and on the reports of the Expert Group.

• Members of the Steering Group, which included Dr John Gray of the Drinking WaterInspectorate, Mr Peter Daley of Allerdale Borough Council, Mr Vic Emmerson ofCopeland Borough Council, Dr Judith Hilton, DoH, Dr David Holt, UKWIR, madesignificant contributions to the research, at the regular meetings, guided and supported theresearch to its conclusion in August 2002.

We are also grateful to Mr Dennis Massey, Deputy Director of Finance, who together with his staffmanaged the funds for the research.

This research would not have been possible without the assistance, support and commitment ofall our colleagues; the names of the many Members and Contributors are listed in the next Section.We apologise if we have inadvertently omitted named individuals in this acknowledgement.

Dr. Stella GohOn behalf of Carlisle and District Primary Care Trust,

North Cumbria.

FundingSupport for this study was provided by the following organisations:

• The Department of Environment, Food and Rural Affairs and its predecessors, theDepartment for Transport and the Regions and the Department of the Environment.(March 1996- August 2002).

• The Department of Health (March 1996- September 1997).

• United Kingdom Water Industry Research Limited (March1998- August 2002).

The study was supervised by the Drinking Water Inspectorate.


Membership

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Membership of North Cumbria Cryptosporidiosis Steering Group

MEMBERS

North Cumbria Health Authority

Dr Stella Goh (Chairman)* Ex CCDC/Honorary Consultant March 1996 to December 2002

Mrs Emma Wigginton Research Assistant March 1996 to September 1997

Miss Joy Williams Research Assistant February 1998 to February 2001

Mr Anthony Pennington Research Assistant March 2001 to December 2002

Dr Nigel Calvert CCDC May 1999 to December 2002

Carlisle Public Health Laboratory

Dr Margaret Knowles* Director March 1996 to December 2002

West Cumberland Hospital Laboratory

Dr Sarah Richards* Consultant Microbiologist March 1996 to December 2002

Allerdale Borough Council

Mr Peter Daley* Environmental Health Unit Manager March 1996 to December 2002

Miss Rachel Horton Environmental Health Officer September 1997 to December 2002

Copeland Borough Council

Miss Catharine Gavin* Principal Environmental Health Officer March 1996 to January 1997

Mr Declan Rowe Principal Environmental Health Officer February 1997 to December 1997

Mr Vic Emmerson Principal Environmental Health Officer January 1998 to December 2002

United Utilities Water Ltd

Mr Keith Osborn* Company Public Health Scientist March 1996 to December 2002

Mr Alan Godfree Team Leader Public Health March 1996 to December 2002

Veterinary Laboratories Agency (Defra)

Mr David Counter Senior Veterinary Investigation Officer June 1997 to December 1999

Mr Andrew Holliman Senior Veterinary Investigation Officer December 1999 to December 2002

Communicable Disease Surveillance Centre, London

Dr Patrick Wall* Consultant Epidemiologist March 1996 to December 1997

Dr Ros Stanwell-Smith Head of Epidemiology Division September 1997 to March 2000

Dr Mark Reacher Consultant Epidemiologist April 2000 to December 2002

PHLS Cryptosporidium Reference Unit

Dr David Casemore* Head March 1996 to December 1999

Dr Rachel Chalmers Head January 2000 to December 2002


Membership

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Drinking Water Inspectorate

Dr John Gray* Principal Inspector March 1996 to December 2002

Project Manager From December 2000

Mr Mark Smith Contracts and Projects Manager March 1996 to December 2000

Department of Health

Dr Judith Hilton* Senior Medical Officer March 1996 to January 1998

Dr Ailsa Wight Senior Medical Officer February 1998 to November 1999

Ms Maggie Tomlinson Principal Environmental Health Officer December 1999 to December 2002

United Kingdom Water Industry Research Limited

Dr David Holt Technical Evaluation Manager September 1998 to December 2002

OTHER CONTRIBUTORS

Communicable Disease Surveillance Centre

Dr James Stuart* Consultant Epidemiologist

Ms Tamara Djuretic Registrar

Dr Sarah O’Brien Consultant Epidemiologist

PHLS Statistics Unit

Ms Clare Gilham Statistician

Mr Neville Verlander Statistician

Mr Andre Charlett Head

Food Safety Microbiology Laboratory

Dr Jim McLauchlin Microbiologist

Drinking Water Inspectorate

Mr Tony Lloyd Superintending Inspector

Veterinary Laboratories Agency (Defra)

Ms Lucy Martindale Administrative Officer

Furness General Microbiology Laboratory

Dr Lenny Griffiths Consultant Microbiologist

Dr Susan Patridge Consultant Microbiologist

Allerdale Borough Council

Mr Bill Potter Team Leader Environmental Health

Mr David Copeland Environmental Health Officer

Mr William Buckley Environmental Health Officer

Mr John Cain Environmental Health Services Manager


Membership

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Copeland Borough Council

Miss Mary Cosgrove Environmental Health Officer

Miss Sharon Blakeley Technical Assistant

Mr Mark Bannon Senior Environmental Health Officer

PHLS Cryptosporidium Reference Unit

Dr Kristin Elwin Clinical Scientist

Ms Anne Thomas Biomedical Scientist

United Utilities Water Ltd

Dr Charmian Kerr Public Health Scientist

Mr Matthew Wilkinson Public Health Scientist

Mr Roy Dunbar Operations Manager

North Cumbria Health Authority

Miss Jennifer Clay Public Health Information Officer

Mrs Joy Graham Senior Public Health Information Officer

Mr Paul Blaylock Public Health Information Assistant

Mr Richard Lamb MIS Manager

Miss Katharine Eccles Typist

Mrs Rona Scott Typist

* Denotes Founder Member


Case-Control Study – Key Points

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Sporadic Cryptosporidiosis Case-Control Study(1 March 1996 - 29 February 2000)

[This is a prospective case-control study into risk factors of primary sporadic cryptosporidiosis in two rural, Local Authorities in the north of England]

Key Points

1. 152 cases were recruited over a period of 4 years.

• 82 (54%) cases were male.

• Median ages of all cases was 4 years with a range of <1 to 55 years.

• Apart from diarrhoea, other prominent symptoms were abdominal pain, vomiting, fever, with a median duration of 9 days.

• All hospital admissions, 23 (15%) were children with a median age of 2 years.

2. A highly significant association was found between cases of cryptosporidiosis and drinkingunboiled tap water in all the water supply zones in the study area (p = 0.001).

• The dose response relationship showed odds of illness increased by approximately 40% with each extra pint of unboiled tap water consumed daily.

• There was no difference in relative risk of Cryptosporidium infection through consuming unboiled tap water in all the different water supply zones, irrespective of whether the water supply zones received water from unfiltered, a variety of conventionally treated and unfiltered or private water supply.

3. A significant association was found between cases and contact with farms, and farmanimals. Multivariable analysis showed short farm visits (p=0.04) and frequency of farmcontact (p for trend=0.02) to be significant.

4. After contact with farm animals, washing hands before eating food may protect individualsfrom Cryptosporidium infection.

5. Microbiological analysis of isolates of Cryptosporidium parvum in the study cases showedthat they were predominantly genotype 2, the strain with a broad host range (humans andanimals).


Intervention Study – Key Points

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Intervention Study (1 March 1996 to 31 August 2002)

[This study examined the impact of membrane filtration on the incidence of cryptosporidiosis in two water supply zones]

Key Points

1. A total of 175 cases were recruited in the six and half years: 153 in the pre - interventionperiod (1 March 1996 - 29 February 2000), 22 in the post intervention period (1 March2000 - 31 August 2002), which included 4 cases in the commissioning period (1 March2000-31 July 2000).

• 51% (90) were male.

• Majority were children <16 years: 88% in pre and 73% in post intervention phase. Median age for overall and pre intervention period was 4 years; post intervention period was 8 years.

• 13% overall (26/175) were admitted to hospital, all were children under 16 years.

• Similar symptoms were recorded in both time periods notably: diarrhoea, abdominal pain, vomiting, loss of appetite and feeling feverish.

2. In the post intervention period, there was a very definite reduction in the incidence ofhuman Cryptosporidium infection in the whole of the study area. The most likely cause ofthis fall is the Foot and Mouth epidemic and the attendant control and containmentmeasures.

3. Despite the confounding effect of the Foot and Mouth epidemic, there was a statisticallysignificant differential decline in incidence rates of human cryptosporidiosis in the watersupply zones of Crummock and Ennerdale, that had new membrane filters installed whencompared with the “Other” zones which had an a variety of conventionally treated,unfiltered and private water supplies and had remained unchanged throughout the studyperiod (p=0.024). This could be attributed to the installation of Membrane filters in thewater treatment works of Crummock and Ennerdale.

4. Risk factor analysis showed drinking unboiled tap water to be a significant risk factor inhuman sporadic cryptosporidiosis infection overall (p<0.001). Risk was not significantlydifferent between different water supply zones. Risk was also significantly increased throughcontact with farms and farm animals (p=0.002) and feeding pets leftovers (p=0.021).

5. Microbiological analysis of the isolates of Cryptosporidium parvum in the study casesconsistently showed the predominance of genotype 2, the strain with a broad host range(humans and animals).


Executive Summary

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Background

Cryptosporidium parvum, a protozoanparasite, is an important cause of gastrointestinal illness in normal, as well asimmunocompromised individuals. It is nowthe third most common, non-viral cause ofgastroenteritis in England and Wales found inabout 2% (range 0.5 to 3.9%) of all faecalspecimens examined in laboratories. Between1991 and 2000, laboratories in England andWales reported an average of 4761 casesannually. Certain regions and districtsreport consistently high incidences ofcryptosporidiosis, which are not attributableto variations in laboratory protocols. In someyears the high incidences may be explained aspart of documented outbreaks, these beingthe subject of rigorous investigations.However, detailed analytical studies have notbeen conducted into routine sporadic cases toascertain the sources of the infection.

Introduction

In 1992, an outbreak of cryptosporidiosisoccurred in Allerdale and Copeland, two localauthorities in North Cumbria. A case-controlstudy conducted during the outbreak showeda statistically significant association betweencases of cryptosporidiosis and consumption ofmains water from Ennerdale. Prior to 1March 2000, Ennerdale and Crummockwater zones supplied unfiltered water whilethe rest of the water supply zones in the twolocal authorities provided a variety ofconventionally treated (coagulation and sandfiltration) and unfiltered water. Following theoutbreak, high levels of sporadic casespersisted in Allerdale and Copeland whencompared with the neighbouring localauthorities of Carlisle City and Eden.

A prospective case-control study was initiatedon 1 March 1996 to examine risk factors inprimary sporadic cases of cryptosporidiosiswithin Allerdale and Copeland and also setout to test the hypothesis that there is adose-response relationship between the risk ofgastroenteritis due to Cryptosporidium and theconsumption of mains water in theCrummock and Ennerdale water supplyzones. The case-control study was initiallyscheduled to cover a period of two and halfyears.

The project was then extended for a furtherfour years to incorporate an InterventionStudy, when it transpired that membranefilters were to be commissioned at theEnnerdale and Cornhow treatment works.(The Cornhow treatment works being thetreatment works for the Crummock watersupply zone). This latter study examinedwhether there were differences before andafter the installation of membrane filters,in terms of the cryptosporidiosis incidencerates, risk factors, and the dose-response relationship between cases ofcryptosporidiosis and consumption of mainswater in the Ennerdale and Crummock watersupply zones. The membrane filters weresubsequently installed between 1 March and31 July 2000. The period before theinstallation of membrane filters, 1 March1996 to 29 February 2000 was the pre-intervention phase and was also thedesignated period for the initial case-controlstudy. The post intervention period extendedfrom 1 August 2000 to 31 August 2002,when data collection ended.

Executive Summary


Executive Summary

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MethodEpidemiological Investigations

The same method was consistently appliedthroughout the six and half years. Cases weredefined as residents of Copeland andAllerdale, who had diarrhoea, and microbio-logically confirmed cryptosporidiosis duringthe period of study. They were primary caseswho had not travelled abroad in the twoweeks before illness. Secondary cases withinthe same household were excluded. Controlswere residents in the same local authorityarea, with no diarrhoea and who had nottravelled abroad in the two weeks prior tointerview. They were identified at randomfrom the GP register, loosely comparable tothe case in three broad age bands 0-5 years, 6-15 years, 16+ years and similar post codesector. The study was designed for threecontrols per case. The case control andintervention studies covered a period of sixand a half years, 1 March 1996 to 31 August2002. Both East and West Cumbria HealthDistrict Ethics of Research Committeesapproved all parts of the research.

A research assistant and deputies followed aset protocol for contacting and interviewingthe cases and controls. Standard letters withappointment times were sent, followed byface to face interviews at home. A speciallydesigned questionnaire was used whichincorporated personal details, travel,exposures to other cases, consumption ofdairy products, salads, raw meats andsausages, pasteurised and unpasteurised milk,water, participation of recreational activity,contact with farm, farm animals, slurry, daycare facilities and type of sewerage. A pictureof a cup, glass, tumbler, mug was shown tointerviewees to assess liquid consumption.Following the interview, an informationleaflet on cryptosporidiosis and the researchwas given to interviewees; the hypothesis ondose response was not mentioned in

all the information to the public. Interviewtimes were routinely recorded. Completedquestionnaires were sent to the PHLSStatistics Unit for data analyses. Cases andcontrols that had previously been interviewedwere not reused; thus avoiding duplicationand data bias.

The study was carried out in two localAuthority areas: Allerdale and Copeland.Postcode location of cases and controlswere transposed onto the different watersupply zones and to be co-terminus with:Ennerdale, Crummock and “Other” (definedas supply areas outwith these two). This wasdone for both studies and essential in theintervention study, in which the comparisonof the effects of the membrane filters was tobe strictly applied to the Ennerdale andCrummock water supply zones. In addition,mixed water supply areas could also beidentified; this allowed data collectedregarding Ennerdale, and Crummock watersupply zones to be analysed exclusively.

Data AnalysisCase-Control Study (1 March 1996 to 29 February 2000)

Single variable analysis was first conducted oneach potential risk factor to estimate oddsratio and 95% confidence intervals (The riskfactor is the risk among those exposed to therisk factor; the odds ratio is the odds of thedisease to non disease in those with the riskfactor). Dose response was investigated usingchi-square test for trends. Analyses wereconducted using the whole data set and thenexcluding individuals receiving mixed watersupply.

Variables with positive association with illnessreaching 20% significance level were includedin a logistic regression model. Terms wereassessed by comparison of nested models


Executive Summary

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using likelihood ratio tests. Variables werethen removed from models if theircorresponding p value was 0.3 or greater, butthe variables of age, sex and water supplyzones were retained, irrespective of theirstatistical significance. Analyses wereconducted using the statistical softwarepackages Epi-info and GLIM.

Intervention Study Incidence rate calculations

Primary cases fulfiling the study criteria wereallocated to the relevant water supply zones:Ennerdale, Crummock and “Other” the watersupply zones outwith Ennerdale andCrummock but within the local authorityboundaries. Ennerdale and Crummock waterhad new Membrane Filters installed in thelatter part of the study period; the “Other”water supply zones did not have any majorchanges to water treatment during the wholestudy period. Cases were then subdivided intofive time frames.

(1) Pre-installation of membrane filters (1March 1996 to 29 February 2000).

(2) Commissioning of membrane filters (1March 2000 to 31 July 2000).

(3) Established membrane filtration prior toFoot and Mouth (FMD) epidemic (1 August 2000 to 20 February 2001).

(4) Established membrane filtration andFMD epidemic (21 February 2001 to20 January 2002).

(5) Established membrane filtrationfollowing FMD epidemic (21 January2002 to 31 August 2002).

Denominator populations of water supplyzones were estimated from informationsupplied and agreed by the water company.Estimation of incidence rates per 100,000person years and 95% confidence intervalswere calculated for the five different timeintervals as listed above, for the defined water

supply zones. Incidence rate comparisonswere then made of those recruited in theperiod before and after the installation ofmembrane filters, for the relevant watersupply zones.

A Poisson Regression model was constructedwith the number of cases of cryptosporidiosisas the predictor variable and the number ofperson years of observation on the offset. Theindependent effect of the MembraneFiltration installation and for the time periodbefore and after Membrane filtrationinstallation were determined separately. Theinteraction between the two was used. Twomodels were applied; one which included thecommissioning period, the other without it.

Risk Factors Analysis

Changes in risk factors for sporadiccryptosporidiosis during the five time periodsof observations as listed previously wereundertaken. Initially, exploratory analysis wasconducted. Five sets of contingency tableswere constructed, one for each time period ofobservation, for each exposure and odds ratioscalculated. Variables significant at p < 0.2 inany of the five sets of contingency tables werereturned for inclusion in logistic regressionmodels. A sequence of multivariable modelswas fitted removing clearly non-significantvariables. An interaction term between thefive time intervals of the study and each of theremaining variables was included in separatemultivariable models to identify a subset ofinteractions for evaluation together in furthermodels. Non-significant interactions wereremoved in order of least significance. Thefinal model consisted of a single interactionterm of total daily volume of tap waterconsumed per day in each of the five intervalsof the study, main effects variables, age, sexand water zone.


Executive Summary

30

Microbiological Investigations

Analysis of stool specimens was carried out bythree local laboratories, which included thelocal Public Health Laboratory. Isolates weresent to the Cryptosporidium Reference Unitfor confirmation and genotyping.

ResultsCase control study- 1 March 1996 to 29 February 2000Reported cases

In the four years of the sporadic case-controlstudy (1996-1999), the number of alllaboratory reported cases of cryptosporidiosisin the study area; Allerdale and Copeland,averaged 52 cases per year (rate = 31.2 per100,000). The highest number, 89 cases(rate=53.9 per 100,000) was seen in 1999 andthe lowest number 24 cases (rate = 14.4 per100,000) was seen in 1997. Allerdale andCopeland consistently showed high incidencerates. The lowest rate in 1997 in the studyarea was still about one and a half timeshigher than the regional and national rates.

Between 1 March 1996 and 29 February2000, two hundred and seven laboratoryconfirmed cases of cryptosporidiosis werereported to the research assistant. Of the 207cases, 55 (26.6%) were not in the studybecause they did not fulfil the study criteria,refused to participate or could not be found.Two notable categories, which did not fulfilstudy criteria, were travel abroad cases6(2.9%) and secondary cases 36(17.4%). Onecase refused to participate, one could not beinterviewed and two who did not respondafter repeated efforts to contact them; thesefour cases could be combined into thecategory of “non-responders” (2%). Similarexclusion criteria were applied to controls.

Recruited Primary cases

Thus, a total of 152 primary cases and 466controls were entered into the study, of these82 (54%) cases and 236 (51%) controls weremale. Three hundred and thirty two (59%) ofthe cases and controls were aged five or underand only 64 (11%) were over 16 years. Themean and median ages of all cases were eightand four years respectively and rangedbetween <1 to 55 years of age. The mainsymptoms were diarrhoea, abdominal painand vomiting with the median duration ofillness lasting 9 days. Twenty- three (15%) ofthe cases were admitted to Hospital; all thesewere children (median age = 2 years; range <1to 14yrs).

Single and multivariable analyses were carriedout in different models, first on total waterconsumed per day; using all data, andexcluding mixed water supply. An additionalmultivariable model examined home tapwater consumed (all data). All the modelsshowed a highly significant associationbetween cases of cryptosporidiosis anddrinking unboiled tap water. The odds perpint of becoming infected withCryptosporidium from drinking total unboiledtap water was approximately 1.40; the 95%confidence interval being 1.14 to 1.71 (p fortrend =0.001).

The dose response relationship for total waterconsumed showed that the odds ofcontracting cryptosporidiosis increased by40% with each extra pint of unboiled waterconsumed daily. There was no evidence of asignificant difference in the risk of becominginfected from consuming unboiled tap waterin the different water zones; irrespective ofwhether the supply was unfiltered, varieties ofconventionally filtered (coagulation and sandfiltration) or private. The results were virtually


Executive Summary

31

the same if consumption of unboiled hometap water was used instead of totalconsumption of unboiled tap water.

A significant association was found withCryptosporidium infection and short farmvisits, contact with farms, farm animals,animal faeces, any other contact with farmanimals, stroking animals on the singlevariable analysis. Multivariable analysesshowed short farm visits (p = 0.04) andfrequency of farm contact (p for trend =0.02)to be significant.

There was a significant association betweencases and eating food within 1 to 2 hours aftercontact with farm animals, in the singlevariable analysis. After contact with farmanimals, washing hands before eating appearsto protect against the infection. A protectiveeffect was also seen with the consumption ofpasteurised milk (odds ratio 0.55 (0.33, 0.91)p=0.02).

All other variables examined were not foundto be risk factors for sporadic cryptosporidio-sis including salads, dairy products, rawsausages, raw meats, pasteurised orunpasteurised milk, ice, bottled water, softdrinks, contact or walk past slurry, swimming,water sports or paddling, contact withplaygroup, contact with anyone withdiarrhoea (outside household), travel in UK,or having different sewage systems.

Intervention Study- 1 March 1996 to 31 August 2002Reported cases

Of the total number (249) of laboratoryconfirmed cases reported to the RA for the sixand a half years period, 207 occurred in thepre intervention period (1 March 1996 - 29

February 2000), 11 cases in the membranefilter commissioning period (1 March 2000 -31 July 2000) and 31 in the post interventionperiod (1 August 2000 to 31 August 2002).

After accounting for secondary cases, travelabroad, and those who refused to participate,there were 153 primary cases in the preintervention period, 4 in the commissioningperiod, and 18 in the post interventionperiod. The marked decrease in cases wasseen in year 2000 and continued into year2001 and 2002 in the post interventionperiod. The reduction was proportionatelygreater in primary than secondary cases. TheFoot and Mouth epidemic had a markedeffect in the study area in 2001.

Recruited Primary cases

A total of 175 primary cases and 537 controlswere recruited for the whole six and a half yearperiod. Of the 175 primary cases, 90 weremale and 85 female. One hundred and fiftythree cases occurred in the pre interventionperiod (1 March 1996-29 February 2000);the locations of these primary cases showed56 in Crummock water supply zone, 43 inEnnerdale water supply zone, and 54 in“Other”. In the post intervention period (1March 2000 to 31 August 2002), there weresix cases in Crummock, three in Ennerdaleand 13 in “Other” water supply zones.

The annual incidence rate of primary sporadiccryptosporidiosis exceeded 10 per 100,000 inthe pre intervention period from 1996 to2000 with a peak of 35 per 100,000 in 1999.In the post intervention period, the incidencedeclined to below 10 per 100,000 in year2000, 2001, and 2002 to the end ofrecruitment in August 2002.


Executive Summary

32

The majority of cases in the total period wereunder 16 years: 88% in the pre interventionperiod and 73% in the post interventionperiod. Comparison of age groups of casesshowed 57% cases in the pre interventionperiod and 41% in the post interventionperiod to be children under five years.

The mean and median age of the totalnumber of cases (175) was 9.1 and 4 yearsrespectively (range <1 to 62). In the preintervention period, the mean and medianage of cases were 8 and 4 years (range <1 to55) respectively; in the post interventionperiod, these were 16.6 and 8 years (range 1to 62).

Diarrhoea and abdominal pain were the twomost common symptoms among cases inboth periods. The median duration ofsymptoms of illness was 9 days (range 2 to 21)in the pre intervention period and 10 days(range 3 to 20) in the post intervention periodrespectively.

In the pre intervention period 23 (15%) caseswere admitted to hospital, and their ages were<1 to 14 years with mean and median age of3.7 and 2 years respectively. In the postintervention period, three cases (14%) wereadmitted to hospital and their ages rangedfrom 3 to 12 years with the mean and medianage of 8.3 and 10 years respectively.

A seasonal spring peak was apparent in casesin the pre intervention period between 1996and 2000, but was no longer conspicuousfollowing the introduction of MembraneFiltration in Ennerdale & Crummock.

The incidence rates per 100,000 person yearsin the populations served by Crummock,Ennerdale, and “Other” water sources weresimilar during the pre intervention period.There was a considerable reduction in

incidence rates of sporadic cryptosporidiosisduring and after commissioning ofMembrane filtration; as well as during andafter the FMD epidemic, which was apparentfor each of the water sources, reflecting bothinstallation of Membrane Filtration and theimpact of the FMD epidemic in livestock.The third of the population living in the“Other” supplies zones continued to receivewater from a variety of conventionally treatedand unfiltered sources. The decline in this“Other” group zone, may therefore beattributed to the FMD epidemic alone.Ennerdale and Crummock water supply zonesexperienced a decline in incidence rate duringand following installation of filters; thisdecline was in excess of that which could beexplained by the FMD epidemic and maytherefore be attributed to the installation ofMembrane Filtration. Poisson regression wasused to examine this aspect.

Poisson Regression

Two models were applied; one included thecommissioning period of the MembraneFilters, the other omitting this time period.

In the first model which included thecommissioning (1 March 2000 to 31 July2000) and the post commissioning period(1 August 2000 to 31 August 2002), theresults showed a significant interactionbetween the two predictors (p = 0.024)indicating that the decrease in incidence inthe water zones with membrane filtration wassignificantly different from the decrease inincidence in the “other” water zones. In thesecond model, the commissioning period wasignored. The results showed a slightlydiminished interaction (p = 0.07).

The estimated incidence rate ratio for the“Other” zones (with no changes throughoutthe study period) was 0.387 (95% C1 0.197


Executive Summary

33

to 0.759) for the time period before and aftermembrane filtration in Crummock andEnnerdale. This could be interpreted as theindependent effect of the FMD epidemic.

For Crummock and Ennerdale water sourceswhere Membrane Filtration was installed,the incidence rate ratio for sporadiccryptosporidiosis post compared to preMembrane Filtration period was estimated tobe 0.156 (95% C1 0.076 to 0.320). Thismeant that the introduction of MembraneFilters was associated with a reduction inincidence of 85.5% (95% C1 68.8% to92.4%) in Ennerdale and Crummock;whereas in the “Other” water zones, thereduction over the same interval was 61.3%(95% C1: 24.1% to 80.3%), a notabledifference.

Risk factors

The interaction term for the risk per pint ofcold unboiled tap water consumed each dayby the five time intervals of the study adjustedfor the other variables in the penultimatemodel was not significant (p=0.12). Theinteraction term was dropped in the finalmodel. Drinking unboiled tap water wasagain shown to be significantly associatedwith sporadic cryptosporidiosis overall [Oddsratio 1.543 (1.212,1.965)(p fortrend<0.001)]. Risk was not significantlydifferent between the different water supplyzones. The risk was also increased by contactwith cow and other farms [Odds ratio 4.532(1.757,11.690) (p=0.002)], and feedingpets leftovers [Odds ratio 3.746(1.214,11.560)(p=0.021)]. A protective effectwas seen for consumption of mixed salad[Odds ratio 0.498(0.266,0.932) (p=0.024)].Most of these impacts were derived from thelarger number of cases in the pre interventionperiod.

No association was detected with age, sex,sewage system of the house, contact withanother person outside the household withdiarrhoea or with feeding pets biscuits.

Microbiological Results

The Cryptosporidium Reference Unit (CRU)confirmed all the isolates of the study casessent to their Laboratory as Cryptosporidiumparvum. Over the five years 1998 to 2002,the Reference Unit received on average 68%of the isolates of cases in the study. Analysisof 84 isolates received by the Reference Unitfrom January 1998 to August 2002, showed70 isolates (83%) were genotype 2, four (5%)were genotype 1, and 10 (12%) could not bedefinitively typed. Cryptosporidium parvumgenotype 2, suggests mammalian (animalsand humans) origins, and genotype 1 signifieshuman origins. The result of thepredominantly genotype 2 in these isolatesstrongly suggests “zoonotic” transmission.This obviously has implications forpreventative measures, in terms of drainageinto reservoirs, contact with grazing livestockand other animals in the vicinity.

Discussion

The main features of the study highlighted inthe above Results Section are discussedextensively in the main text of the Report.The “Discussion sections” have not beenincluded in this Executive Summary as theycontain detailed comparisons with otherstudies, and discursive exploration of theliterature on pertinent topics. Readersinterested, should refer to the relevantsections of the Main Report, under Sporadiccase-control Study - Discussion; andIntervention Study - Discussion.


Executive Summary

34

Conclusions

Sporadic case-control Study

This protracted four year longitudinal casecontrol study in two rural communities inNorth Cumbria has identified important riskfactors of sporadic cryptosporidiosis.

The results showed a highly significantassociation (p=0.001) between illness in casesand drinking unboiled tap water in all thewater supply zones in the local authorities ofAllerdale and Copeland in North Cumbria. Adose-response relationship was also found,with the odds of illness increasingby approximately 40% with each extrapint of unboiled water consumed daily. Therisk of Cryptosporidium infection throughconsuming water in the different water supplyzones was the same, irrespective of whetherthe water supply zones received water that wasunfiltered, a variety of conventionally treatedand unfiltered or private.

There were also significant associationsbetween cases and short farm visits, contactwith farms, farm animals, animal faeces, anyother contact with farm animals, strokinganimals, and frequency of farm visits in thesingle variable analysis. Short farm visitsremained significant in the multi-variableanalysis (p=0.04), as well as frequency of farmcontact (p=0.02).

Eating food within 1-2 hours of contact witha farm animal was found to be a significantrisk factor in the single variable analysis.Washing hands before eating, after visits tofarms appears to protect against the infectionin the multivariable analysis which excludedindividuals with mixed water supply.

Microbiological analysis of isolates of casesshowed that they were predominantly

Cryptosporidium parvum genotype 2, thestrain with a wide host range, including farmanimals.

Several public health messages concerningcryptosporidiosis should be re-emphasised,such as washing hands before eating food,after contact with farm animals; and “boilingpotable water”, the advice given by the ChiefMedical Officer to doctors for the immune-compromised.

Intervention Study

This study examined the impact of theinstallation of membrane filters on theincidence of Cryptosporidium infection in twowater supply zones (Ennerdale andCrummock), and compared the results withthe “other” water supply zones that did notexperience change in North Cumbria. Riskfactors were also explored.

The results show that in the post filtrationperiod of this study there was a very clearreduction in the incidence of sporadiccryptosporidiosis in the whole study area. Themost likely cause of this reduction was theFMD epidemic and the attendant control andcontainment measures adopted. This wouldhave applied equally to all the different watersupply zones. However, there was a greaterreduction in the incidence rates within theCrummock and Ennerdale water supply zonesthat had new membrane filters comparedwith the other water supply zones that didnot. Thus, despite the confounding effect ofthe FMD epidemic, the statisticallysignificant differential decrease in theincidence rates of sporadic cryptosporidiosisin these particular water zones could beattributed to the installation of MembraneFilters.

Drinking unboiled tap water remained a


Executive Summary

35

highly significant risk factor overall(p<0.001). Risk was not significantly differentbetween the water supply zones. Risk was alsoincreased by contact with cow and otherfarms (p=0.002) and feeding pets leftovers(p=0.021).

Microbiological analysis on the isolates for thewhole study period, consistently showedCryptosporidium parvum genotype 2 to bepredominant for the whole of the studyperiod. The differential dominance ofgenotype 2 (animals and humans strain) overgenotype 1 (the human strain) suggestszoonotic transmission.


Section IEpidemiological

Study


BackgroundCryptosporidium, a protozoan parasite, wasdiscovered in 1907 by Tyzzer, in mice [1].The first human case of Cryptosporidiuminfection was reported in 1976 in the USA[2]. In the late 1970s and early 1980s,Cryptosporidium was considered anopportunistic pathogen, affecting AIDS andimmuno-compromised individuals. However,it has emerged as an important cause ofgastro-intestinal illness in both the immuno-compromised and immunocompetent [3, 4, 5, 6].

Cryptosporidium parvum is now the third mostcommon cause of non-viral gastro-enteritis inEngland and Wales, after campylobacter andsalmonella [7, 8]. The Public HealthLaboratory Service (PHLS) survey in 1990,estimated Cryptosporidium accounted for 2%(range 0.5% to 3.9%) of all faecal specimensexamined in the 16 participating laboratories[9]. It is likely that laboratory isolatesrepresent only a small proportion of theCryptosporidium infection in the community.

Cryptosporidium infection can beasymptomatic. In immuno-competentindividuals, it presents as a self-limitinggastro-intestinal illness characterised byprofuse, offensive, watery diarrhoea andabdominal pain. Nausea, vomiting, anorexia,weight loss and fever have also been reported.Duration of illness is on average nine days(range: few days to two weeks). The highestincidence is in the 1-4 year olds with anothersmall peak in the 15-44 years age group.Among immunocompetent individualsinfected, children are the most likely to be

hospitalised. In certain cases in the immuno-compromised, cryptosporidiosis may besevere, protracted, potentially life threateningillness with complications affecting the liver,biliary tract, pancreas and respiratory system.Diarrhoea may persist for weeks, months andeven years and can be intermittent. Thehighest incidence in the immuno-compromised is usually in adults between 31- 40 years, reflecting the age of AIDS sufferers[10, 11, 12, 13]. There is no specificantibiotic for treatment of cryptosporidiosis.Recently, the introduction of highly activeanti-retroviral therapy (HAART) hascontributed to the improved prospects ofmany AIDS patients with this infection [12,14].

Cryptosporidium parvum has a worldwidereservoir in wild and domestic animals such ascalves, lambs, pigs, deer, goats, rabbits,monkeys, cats, dogs, rodents and birds [15,16, 17]. Human infection has been reportedfrom over 90 countries and six continents[16]. Human cryptosporidiosis is the result ofingestion of Cryptosporidium oocyst, aspherical ovoid body 4-6 microns in diameter,excreted by infected animals and humans.Transmission has been documented fromdirect contact with farm animals particularlycalves and lambs [17-21], indirectly fromcontaminated foods [3, 16, 22], milk [3],private and mains water [12, 23-33]; waterfrom recreational pools [34-37] or fromanother infected individual [38, 39, 40].Rural zoonotic infections are more frequentlyassociated with farms and farm animals andcan involve farm workers and veterinarypractitioners [41-43].

SECTION I

Introduction


Introduction

40

Urban infections are usually associated withsecondary transmission within families [38,40], day care centres [38, 39], and hospitals[44, 45]. Under-developed countries areknown to have a higher incidence ofcryptosporidiosis [46]. It is an importantcause of traveller’s diarrhoea, affecting notonly travellers in areas of high incidence, butalso at holiday resorts in Europe, whereoutbreaks have occurred [47].

Epidemiological investigations had primarilybeen focused on outbreaks rather thansporadic cases. Water-borne outbreaks in theUSA and United Kingdom (UK) causewidespread concern because potentially, largenumbers of people in the community couldbe affected [12, 23-33]. The most notableoutbreak in Milwaukee, USA, in 1993,affected an estimated 403,000 persons [28].Several large outbreaks involving hundreds ofpeople have also been documented in the UK,such as those in Swindon and Oxfordshire in1990, [25] South and West Devon in 1995[32], North West England in 1999 [33].

In response to the Swindon and Oxfordshireoutbreak, the Department of theEnvironment and the Department of Healthjointly convened the Expert Group onCryptosporidium in Water Supplies, under thechairmanship of the late Sir John Badenoch.The Expert Group was asked to review theSwindon and Oxfordshire and otheroutbreaks and to report on the significance ofCryptosporidium in water supplies.

The Expert Group sat throughout the 1990sand is currently active under thechairmanship of Professor Ian Bouchier.Three reports have been made to Ministersand more than $2 million have been allocatedto carrying out research recommended by theExpert Group [12,17,48]. The recommenda-tions and research outputs from the ExpertGroup that are most relevant to this study

include: the importance of the multiplebarrier approach to water treatment, theconcept of planning for management ofoutbreaks and rehearsal of contingency plans,and a consistent and methodologicalapproach to surveillance and epidemiologicalstudies.

Cryptosporidiosis is not a notifiable disease[49]. Surveillance in England and Wales isbased on voluntary reports from laboratories.Whilst there may be variations in laboratorymethods and protocols in the country, manylaboratories now include Cryptosporidium inroutine diagnostic tests of stool specimens. InEngland and Wales, between 1991 and 2000,the total number of laboratoryCryptosporidium cases averaged 4761 annually(range: 3660 to 5797) [50]. Regionalvariations can be seen from one year to thenext. Three regions: the North West, SouthWest, and Northern and Yorkshire, featuredconsistently higher rates than the Englandand Wales average [50, see Results: Table 5].High annual incidence in certain years wasdue, in part, to documented outbreaks.However, in the many years withoutoutbreaks, the consistently high annualincidence of sporadic cases in some areas hasbeen largely unexplained.

The 1990 PHLS survey found considerablevariation in the prevalence of Cryptosporidiuminfection amongst 16 participatinglaboratories. The higher prevalence in ruralareas was not considered to be due to variationin laboratory methods. No seasonal variationwas observed but sudden infrequentcommunity-wide increases of Cryptosporidiumwas thought to be due to undetected commonsource infections [9].

A ten-year retrospective analysis of laboratoryreports (1990 - 1999) was carried out in theNorth West region, compared six HealthAuthorities, which had been affected by a


Introduction

41

single water supply, with other HealthAuthorities in the region. The study foundthat excess numbers of cases was due torecurrent peaks of infection in the six HealthAuthorities. It was suggested that the excesseswere not seasonal peaks, as they varied fromone year to the next, but may have been dueto unrecognised outbreaks from a recurrentsource, possibly from an unfiltered watersupply [51].

A detailed longitudinal case-control study inan area of consistently high incidence ofsporadic cases of cryptosporidiosis, willtherefore be useful to elucidate risk factorsand to establish whether the high incidence isdue to a single putative endemic source, ormultiple unrelated causes.

IntroductionIn 1992, an outbreak of cryptosporidiosisoccurred in Allerdale and Copeland, two localauthorities in North Cumbria. (WestCumbria and East Cumbria wereamalgamated to form North Cumbria in1996). A case control study conductedduring the outbreak showed a statistically

significant dose-response relationshipbetween consumption of unboiled mainswater from the Ennerdale water supply andCryptosporidium gastroenteritis. There werealso a small number of cases in theCrummock water supply zone, which did notshow a statistically significant association withconsumption of unboiled mains water. Theoutbreak control team concluded that thestudy suggested but did not prove that theoutbreak was associated with consumption ofunboiled mains water from the Ennerdalewater supply [52]. Prior to March 2000, themains water supply for both Ennerdale andCrummock water supply zones wasunfiltered, whilst the rest of the water supplyzones in Allerdale and Copeland received avariety of conventionally treated andunfiltered water.

Following the outbreak, high levels ofsporadic cases persisted in Allerdale andCopeland, compared to the neighbouringlocal authority areas of Carlisle City andEden. [Table 1]

YearLocal

Authorities

Allerdale &

Copeland

Carlisle &

Eden

Allerdale &

Copeland

Carlisle &

Ed

Table [1] Number of cases, Incidence rate of Cryptosporidiosis and ratio of Salmonellosis to

Cryptosporidiosis

Ratio of Salmonellosis/

Cryptosporidiosis

1993

0.9

2.33

39.7

18.2

Cases of

Cryptosporidiosis

Cases / 100,000

residents

1994

67

27

54 32.3 1.8

36 23.9 2.5

Allerdale &

Copeland

Carlisle &

Eden

Allerdale &

Copeland

Carlisle &

Eden

1994

1995

54

30

32.3 1.8

36 23.9

19.9 3.2

2.5

52 31.1 2.2

Higher ratios of cryptosporidiosis to salmonellosis in Allerdale and Copeland were also observed.

TABLE 1 NUMBER OF CASES, INCIDENCE RATE OF CRYPTOSPORIDIOSIS AND RATIOOF SALMONELLOSIS TO CRYPTOSPORIDIOSIS


Introduction

42

Towards the end of 1993, a meeting wasconvened to discuss the proposal for a studyinto sporadic cryptosporidiosis. All theinterested parties who attended stronglysupported the study. These included repre-sentatives from Local and Health Authorities,Consultant Microbiologists, Experts from theReference Laboratory, Drinking WaterInspectorate, Department of Health and theWater Company.

The case-control study into sporadic casesbegan on 1 March 1996 and was initiallyscheduled for 18 months. It was extended foranother year because of the low number ofcases in the second year. In 1998, members ofthe steering group agreed to the continuationof the case-control study as an interventionstudy, when it became known that membranefilters were to be commissioned at theEnnerdale and Cornhow treatment works.(The Cornhow treatment works suppliesdrinking water to the Crummock watersupply zone). The study subsequentlycontinued till 31 August 2002, as anintervention study.


Aims

I Case-control study into sporadic cases (1 March 1996 - 29 February 2000)

To determine whether the sporadic cases of cryptosporidiosis occurring in the Allerdale andCopeland local authorities are associated with a common risk factor(s), and to test thehypothesis that there is a dose-response relationship between the risk of gastro-enteritis dueto Cryptosporidium and the consumption of mains water in the Crummock and Ennerdalewater supply zones.

II Intervention study (1 March 1996 - 31 August 2002)

Membrane filters were commissioned at Ennerdale and Cornhow Water Treatment Works(WTW), (the latter being the treatment works for Crummock water supply zone) betweenthe 1 March 2000 and the 31 July 2000. The pre intervention period was defined as 1March 1996 to the 29 February 2000 and the post intervention period as 1 August 2000 to31 August 2002.

To determine whether there are any differences before and after the installation ofmembrane filters in Ennerdale and Cornhow treatment works in terms of :-

1) Incidence rates of cryptosporidiosis in the water supply zones of Ennerdale and Crummock.

2) Cryptosporidiosis and association with risk factors in the same areas.

3) Dose-response relationship between the risk of gastro-enteritis due tocryptosporidiosis and consumption of mains water in the Ennerdale and Crummock water supply zones.


Methods

Sporadic Case Control StudyThe study period covered 1 March 1996 to 29February 2000, before the installation ofmembrane filters at Ennerdale and Cornhowwater treatment works. Within Allerdale andCopeland, the study areas, there were twolarge zones, Ennerdale and Crummockreceiving unfiltered water supply; the “other”water zones out-with Ennerdale andCrummock received a variety ofconventionally treated (coagulation and sandfiltration), unfiltered water, and private watersupplies (see Section III). No change hadtaken place in any of the water supply zonesduring this study period. Water supply zonesboundaries are not co-terminus with localauthority boundaries.

Intervention StudyThe Intervention Study covered the wholeperiod of 1 March 1996 to 31 August 2002.Membrane filters were commissioned at thetwo water treatment works at Ennerdale andCrummock, between 1 March 2000 and 31July 2000. The study compared the postintervention period (1 August 2000 to 31August 2002) with the pre-interventionperiod (1 March 1996 to 29 February 2000)in the water supply zones of Ennerdale andCrummock to study the effects of themembrane filters.

The same method for contacting andinterviewing cases was applied throughout thewhole, uninterrupted period of six and a halfyears.

Although the study was conducted in thewhole of the two local authority areas,Allerdale and Copeland only Ennerdale andCrummock water supply zones experienced

the intervention, i.e. the membrane filtersinstallation. No change had taken place inthe “other” water supply zones outwithEnnerdale and Crummock water supplyzones, but within the local authorities. Casesand controls were allocated to the appropriatewater supply zones after the interviews, frompostcodes information, which was particularlypertinent to the Intervention Study (seeSection III water supply zones).

Ethical Approval and Steering GroupThe East and West Cumbria Ethics ofResearch Committees gave ethical approvalfor all parts of the research. A Steering Groupcomprising of all relevant parties, includingthe Department of Health, Drinking WaterInspectorate, Department for Environment,Food and Rural Affairs (Defra), UnitedKingdom Water Research Limited (UKWIR)Consultant Microbiologists, Water Company,Local Authorities and the Health Authoritymet on a regular basis to oversee the progressof the study.

Communication with doctors and publicGeneral Practitioners and hospital doctorswere informed on three occasions about thestudy; at the start, when the study wasextended and the appointment of a thirdresearch worker in 2001. Doctors were givendetails about the study, which included a copyof the information leaflet given tointerviewees. Press releases were issued at thestart of the study and in 1998, to explain thecontinuation of the study (because of lownumbers of cases). Local and national presscoverage of cryptosporidiosis was monitored,during the six and a half years of the study.


Methods

45

A seven-month survey was conducted in 1999to examine whether the study population hadbeen influenced by increased media coverageat the time (Media Interest Study).

Study designThe case-control study into sporadic cases wasdesigned for a period over one year with threecontrols per case. The sample size estimationfor the case-control study was that 41 caseswould be sufficient to give 80% power todetect an odds ratio of 3 or more with 95%confidence if 30% to 40% of controls areexposed (for example by consuming 2+ glassesof water per day).

Research assistant and deputiesFor the whole period of the study, threeresearch assistants (RAs) were appointed, eachfor different periods of the study. Twoenvironmental health officers (EHOs), onefrom each local authority covered the absencesof the research assistant. The same leadconsultant trained all the research assistantsand EHOs. At certain intervals, the RAs andEHOs accompanied each other on interviewsto ensure the interview method wasconsistently applied. The guidance forinterviewers, set out in the Bouchier Reportwas followed.

The StudyAll laboratory confirmed cryptosporidiosiscases of residents in Copeland and Allerdalewere eligible for inclusion in the study from 1March 1996 to 31 August 2002.

Three local laboratories: the Carlisle PublicHealth Laboratory, the West CumberlandHospital Microbiology Laboratory and theFurness General Microbiology Laboratoryconducted diagnostic analysis on stoolspecimens. Isolates were sent to theCryptosporidium Reference Unit for

confirmation from 1996 and genotypingfrom 1998 [see Section II].

Following the agreed protocol, all laboratoryconfirmed cases in Allerdale and Copelandwere reported to the Research Assistant asthey occurred. Standard introductory letterstogether with appointment times were sent tocases for early investigations at home. Severalattempts would be made to contact the case;home visits would still be made, even if noreply were received. Refusals, non-contactable cases and non-responders werenoted. A standard protocol for contactingcases and controls was devised to ensure allinterviewers followed the same method(Appendix 7).

Case definitionA case was defined as a resident in the twonamed Local Authorities with diarrhoea;microbiologically confirmed to haveCryptosporidium (and no other pathogen)from a routine faecal sample submitted to thelocal laboratories; onset of symptoms duringthe years of the study; no known contact witha case of cryptosporidiosis or contact with ahousehold member with symptoms ofdiarrhoea in the two weeks prior to onset ofillness; and no travel abroad in the two weeksbefore illness. Cases that did not fulfil thecriteria and outbreak cases were excluded.

Control definition and selectionControls were defined as residents in theAllerdale and Copeland local authority areas,with no diarrhoea and who had not travelledabroad in the two weeks prior to interview.Controls were to be identified at random andloosely comparable to the case for age in threebroad age bands 0-5 years, 6-15 years, 16+years and resident in a similar post code area.The control selection was made using a


Methods

46

Microsoft Access® macro routine designed byIT staff at the Health Authority to extractpatient details from the general practitionerpatient register (Exeter) system, stratified inaccordance with the age band and postcodecriteria for the particular case. The postcodeselection criterion was based on using the firstfour, five or six digits of the respective six,seven or eight digit full postcode for the case(exclusive of the space between the first andsecond group of digits). Once all potentialcontrols on the EXETER system thatmatched the selection criteria had beenidentified, they were numbered individuallyon a table. A sample of controls was thengenerated by running a Structured QueryLanguage command using the randomisedfunction. The name, address, age and generalpractitioner of potential controls for each casewas then printed.

Initially, controls were selected and listed atthe Health Authority in batches of five for theresearch assistant to recruit the required threecontrols, in accordance with the studyprotocol. If the required number could not berecruited from the first batch, a further fivepotential controls were requested and noted asan extra set drawn. The names from the list ofpotential controls were checked against casesand controls already recorded in the Access®administrative database maintained by theresearch assistant. As the research progressed,by the year 2000, the batch size for potentialcontrols was increased to ten, to avoidduplication of controls and cases already inthe research. Controls for contact wereselected from the randomly generated list instrict sequential order on the list. Cases andcontrols were not duplicated in the study.Controls that had a household memberalready in the study or had been contactedand interviewed previously were not used.

Following the same procedure as the case,specially prepared introductory letters with

appointment times were sent to controls, andfollowed by visits to interview controls athome. Three consenting controls fulfiling thecriteria set down in the protocol wereco-opted for each case, from the list ofneighbourhood controls generated by theHealth Authority, as described above. Casesand controls were interviewed as early aspossible after the date of reporting;sometimes, this included out of hours andweekend interviews.

QuestionnaireA specially designed questionnaire was usedfor the face-to-face interviews of cases andcontrols at home. Telephone interviews wereconducted on request, and were offeredduring the Foot & Mouth outbreak.Interviews were conducted directly with theinterviewee if over 18 years or with theirparent/guardian present if under 18 years,unless the interviewee requested to beinterviewed separately and the parent/guardianconsented to this. Cases and controls wereasked to verify their personal details includingoccupation and questioned about: recentillness; travel; household contacts withdiarrhoea; contact with cases ofcryptosporidiosis; consumption of mains andbottled water; exposures to recreational water;consumption of various foods, dairy products,milk, salads, raw vegetables, raw sausages andother uncooked meats; contact with farms,farm animals, pets, fields sprayed with slurry;attendance at day care facilities, in the twoweeks prior to illness for the cases and, for thecontrols, two weeks prior to interview. Astandard pictorial leaflet of a cup, glass,tumbler, and pint mug was shown to theinterviewee to assess liquid consumption.

The same basic questionnaire was usedthroughout the study. After an initial period,certain questions were expanded, for example,contact with animals, to allow for differentanimals to be incorporated. In 1998, the


Methods

47

questionnaire was revised to facilitate dataentry and data entry boxes were added;however no changes were made to the text.

On completion of the questionnaire, aleaflet with questions and answers oncryptosporidiosis and information about thestudy was given to the interviewee. Writtenconsent was obtained for all cases andcontrols. Case refusals and those with publichealth concerns were reported to theenvironmental health department.

Following the interview, post-codes of allcases and controls were translated to localauthority areas and water supply zones fromgeographical information system (GIS)information provided by the Water Company.This also allowed identification of districtmeter areas (DMAs) with mixed watersupplies, for the whole of the study period.[See section III on Water Supply Zones].

Administrative databaseAn administrative database was developed inMicrosoft Access® by the Health Authorityto record all the cases and controls in thestudy. This database was designed to recordcomprehensive details such as date ofinterview of cases and controls; excluded casesand reasons for exclusion; and microbiologicaldetails including genotype. All the completedquestionnaires were sent to The PHLSStatistics Unit, for double entry data inputand analysis. Only primary cases fulfiling thestudy criteria were considered for statisticalanalysis.

ValidationAll the primary cases for inclusion in thestudy and reasons for excluded cases wereperiodically reviewed and reported to theSteering Group. Similarly, the reasonscontrols that were contacted but did not takepart were also noted. These exclusion reasonsare described in the section in Results 4, B, C.In June 2002, a validation exercise found that3 cases and 8 controls were excluded for travelin the UK for more than 7 days. These werechecked; 2 cases and 3 controls subsequentlyfound to be travel within the UK werere-introduced into the Intervention Studyanalysis. The remaining one case and 5controls remained excluded, for travel abroadand contact with a case of diarrhoea.

Data AnalysisThe PHLS Statistics Unit conducted theanalysis for both the sporadic case-controlstudy and Intervention Study.

Analyses were done using the statisticalsoftware packages Epi-Info [53] and GLIM[54]. Both the reports for sporadic case-control study and the Intervention Study areset out in the Results section.


Results : Incidence

48

Results

Ai) Reported cryptosporidiosis:annual incidence in Allerdaleand Copeland; 1 March 1996- 31 August2002[Table: 2]

The North Cumbria cryptosporidiosisstudy began on 1 March 1996 andcontinued uninterrupted until 31August 2002. During this period, alllaboratory identifications ofcryptosporidiosis of residents in thelocal authorities of Allerdale andCopeland were reported to theResearch Assistant (RA). Table 2shows the monthly reported casesduring the study period.

Membrane filters were installed atEnnerdale and Cornhow treatmentworks between 1 March 2000 and 31July 2000. In the four years prior tomembrane filtration, 1996-1999, anaverage of 52 laboratory cases werereported annually. The highestnumber, 89 reported cases, was seenin 1999, and the lowest number, 24cases, was in 1997. A marked seasonalincrease was observed each spring inthe months of April, May, and Junewith a smaller increase in September,October, and November. A cluster ofcases in April 1999 was investigated,but was not found to be an outbreak.

Following the installation ofmembrane filters in July 2000, 14cases were reported between 1 August2000 and 31 December 2000. Thiscontrasted with a mean of 12 caseseach year (range 7-17) between 1996and 1999 for the same period.Overall, in year 2000, only 27 caseswere reported for the whole year,representing one third of that seen in

1999, but was similar to the 24 casesseen in 1997. Year 2001 was the yearof the Foot and Mouth Outbreak.Very few cases were reported in thestudy area; the experience was similarto other parts of the District andnationally.


Results : Incidence

49

TA

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199

4 T

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1994

1995

1996

1997

1998

1999

2000

2001

2002

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CB

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10

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10

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33

11

20

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10

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Mar

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24

32

50

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22

42

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20

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37

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75

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83

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614

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37

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56

39

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12

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Results : Incidence rates

50

A ii) Reported cryptosporidiosis:Incidence rates in Allerdaleand Copeland. Comparisonswith Carlisle City and Eden,regionally and nationally. 1 March 1996 - 31 August2002 [Tables: 3, 4, 5]

Examination of annual incidence ratesof reported cryptosporidiosis inAllerdale and Copeland between 1996and 1999, prior to installation ofmembrane filters, showed on averagean annual incidence rate of 31.2reported cases per 100,000 for thetwo local authorities. The highestannual incidence rate of 53.9 casesper 100,000 was seen in 1999; thelowest annual rate of 14.4 per100,000 was in 1997 [Table3].

Comparison of the annual incidencerates of Allerdale and Copeland withneighbouring local authorities ofCarlisle City and Eden between 1996and 1999 showed the study area tohave similar or lower incidence ratesin 1996 and 1997, but higherincidence rates in 1998 and 1999. In1999, the incidence rates in Allerdaleand Copeland was almost twice thatin Carlisle City and Eden [Table 3].

Allerdale and Copeland together withthe District, North Cumbria, showedconsistently higher annual incidencerates of reported cryptosporidiosis,compared with the Northern andYorkshire region and England andWales between 1996 and 1999 [Table4]. The lowest incidence rate in 1997in the study area was still about oneand a half times the regional andnational rates. The highest incidencerate in 1999 in Allerdale and

Copeland was six times the regionaland national rates.

In Year 2000, membrane filters wereinstalled at Ennerdale and Cornhowtreatment works. The annualincidence rate of reported cases inAllerdale and Copeland (16.4 per100,000) was half of that of CarlisleCity and Eden for the year 2000[Table 3].

In 2001, Foot and Mouth disease wasprevalent throughout the study area,in the District and many parts of thecountry; low incidence rates of cryp-tosporidiosis were seen in many localauthorities. Allerdale and Copelandshowed a slightly lower annualincidence rate of 6.1 cases per100,000 compared to 7.3 cases per100,000 for the District, but wassimilar to 6.9 cases per 100,000 forEngland and Wales [Table 4].

Allerdale and Copeland are localauthorities in North Cumbria district,which is part of Northern andYorkshire region. In the ten years1991 - 2000, the annual incidencerate of all reported cases, whichincluded both sporadic and outbreakcases, in Northern and Yorkshireregion, was the third highest inEngland and Wales, following theNorth West and South West region[Table 5].



51

1993 1994 1995

No Rate No Rate No Rate

Allerdale 34 35.3 35 36.4 33 34.4

Copeland 40 56.0 19 26.8 19 26.9

Total 74 44.2 54 32.3 52 31.2

Carlisle 19 18.5 19 18.4 17 16.4

Eden 13 27.8 17 35.9 13 27.1

Total 32 21.4 36 23.9 30 19.8

NCHA 106 33.4 90 28.3 82 25.8

TABLE 3 DISTRICT REPORTED CASES OF CRYPTOSPORIDIOSIS BY LOCAL AUTHORITY INNORTH CUMBRIA 1993 TO 1995 NUMBERS/RATES PER 1000,000

1996 1997 1998 1999 2000 2001 2002*

No Rate No Rate No Rate No Rate No Rate No Rate No Rate

Allerdale 20 20.9 13 13.5 29 30.2 50 52.4 19 20.0 7 7.4 5 5.3

Copeland 22 31.1 11 15.6 23 32.9 39 55.9 8 11.6 3 4.3 2 2.9

Total 42 25.2 24 14.4 52 31.3 89 53.9 27 16.4 10 6.1 7 4.3

Carlisle 22 21.3 23 22.3 14 13.6 18 17.6 27 26.5 10 9.8 5 4.9

Eden 16 32.9 18 36.4 24 47.9 27 53.7 21 41.4 3 5.9 7 13.8

Total 38 25.0 41 26.9 38 24.8 45 29.5 48 31.5 13 8.5 12 7.9

NCHA 80 25.2 65 20.4 90 28.2 134 42.2 75 23.7 23 7.3 19 6.0

DISTRICT REPORTED CASES OF CRYPTOSPORIDIOSIS BY LOCAL AUTHORITY IN NORTHCUMBRIA 1996 TO 2002 NUMBERS/RATES PER 1000,000

N.B.* To 31/08/2002Source Public Health Medicine North Cumbria Health Authority / Carlisle &District PCT from1 April 2002



52

Nu

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100,0

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00

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00

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00

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5797

10.9

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4321

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24

14.4

Are

a

1996

1997

1998

1999

2000

*2001

Note

s

*In

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des p

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data

for

Engla

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Wale

s

Sou

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um

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AL

HE

AL

TH

AU

TH

OR

ITY

AN

D E

NG

LA

ND

& W

AL

ES1

996

TO

200

1



53

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Northern &

Yorkshire 618 806 749 801 765 678 498 516 576 463

Trent 466 503 462 526 573 344 468 402 536 705

Eastern 394 486 488 352 626 283 589 273 419 480

London 546 234 205 176 257 168 161 135 205 267

South East 982 555 710 687 872 502 558 526 416 805

South West 706 709 565 595 1071 451 490 508 605 715

West

Midlands 334 414 452 261 397 346 291 313 434 588

North West 778 1166 859 704 754 666 1044 801 1233 1417

England total 4824 4873 4490 4102 5315 3438 4099 3474 4424 5440

Wales 341 338 342 331 376 222 221 271 335 357

England +

Wales total 5165 5211 4832 4433 5691 3660 4320 3745 4759 5797

Scotland 982 954 900 865 732 618 690 879 598 867

Northern

Ireland 149 58 177 89 81 98 82 180 181 417

UK 6296 6223 5909 5387 6504 4376 5092 4804 5538 7081

Source Public Health Laboratory Service Topics A to Z. Last accessed 24/09/2002 at http://www.phls.co.uk/topics_az/crypto/data_all.htm

Table 5 United Kingdom Number and Incidence Rates for Cryptospordium Laboratory Reports 1991 - 2000

Cryptosporidium LABORATORY REPORTS

United Kingdom, All identifications, 1991 - 2000

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Northern &

Yorkshire 9.8 12.8 11.8 12.7 12.1 10.7 7.9 8.1 9.1 7.3

Trent 9.3 9.9 9.1 10.3 11.2 6.7 9.1 7.8 10.4 13.7

Eastern 7.7 9.4 9.4 6.7 11.9 5.3 11.0 5.1 7.7 8.8

London 7.9 3.4 3.0 2.5 3.7 2.4 2.3 1.9 2.8 3.6

South East 11.9 6.7 8.5 8.2 10.3 5.9 6.5 6.1 4.8 9.2

South West 15.0 14.9 11.8 12.4 22.2 9.3 10.0 10.4 12.3 14.4

West

Midlands 6.3 7.8 8.5 4.9 7.5 6.5 5.5 5.9 8.1 11.0

North West 11.8 17.7 13.0 10.6 11.4 10.1 15.8 12.1 18.7 21.4

England total 10.0 10.1 9.3 8.4 10.9 7.0 8.3 7.0 8.9 10.9

Wales 11.8 11.7 11.8 11.4 12.9 7.6 7.6 9.2 11.4 12.1

England +

Wales total 10.1 10.2 9.4 8.6 11.0 7.0 8.3 7.1 9.0 10.9

Scotland 19.2 18.7 17.6 16.9 14.2 12.1 13.5 17.2 11.7 17.0

Northern

Ireland 9.3 3.6 10.8 5.4 4.9 5.9 4.9 10.7 10.7 24.6

UK 10.9 10.7 10.2 9.2 11.1 7.4 8.6 8.1 9.3 11.8

* The Regional Office boundaries were revised from 1 April 1999. Earlier years figures have been revised to reflect theses changes

Incidence rates by Health Regional Office areas of England*, Wales, Scotland & Northern Ireland

Population estimates used to calculate rates from PHLS Laboratory report data above are those published by ONS Health Statistics Quarterly

10 / Summer 2001

Projections are based on mid-1996 population estimates, consistant with the national projections produced by the Government Actuary's

Dept.

TABLE 5 UNITED KINGDOM NUMBER AND INCIDENCE RATE FOR CRYPTOSPORDIUMLABORATORY REPORTS 1991 - 2000

INCIDENCE RATES BY HEALTH REGIONAL OFFICE AREA OF ENGLAND*, WALES,SCOTLAND & NORTHERN IRELAND


Exclusions

54

B i) “Exclusions” Definition.

All laboratory confirmed cases ofresidents in the study area, Allerdaleand Copeland, were routinelyreported to the research assistant asthey occurred, during the studyperiod. Controls were selected foreach case matched for the relevant agegroup and similar post-code sector.Cases and controls were encouragedto participate in their respectiveletters of introduction (see Methodssection).

Prior to conducting the interviews,there were cases and controls who didnot participate; the reasons werefound to be refusals, failure torespond, could not be interviewed,non residents of study area, duplicatesof cases and controls already in study.

From information received atinterviews, there were also cases andcontrols who did not fulfil the studycriteria; such as cases and controlswho had travelled abroad, cases whohad contact with another case ordiarrhoea in the household, andcontrols with diarrhoea.The separation of all these cases andcontrols from the list for statisticalanalyses was conducted with care.This section lists all these separatedcases and controls with the reasonsfor the separation set out in differentcategories. The definition of“exclusions” therefore, was all thecases and controls that were eligiblebut did not participate in the study,and included cases and controls thatdid not fulfil the study criteria.

a) Sporadic case-control study: 1March 1996 - 29 February 2000Case exclusions and exclusionreasons (Table 6, 7, 8)

Table 6, 7, 8 shows the results of theanalysis of the case exclusions andreasons for the exclusions, for thesporadic case-control study. A total of207 laboratory confirmed cases wasreported to the research assistantduring the period 1 March 1996 - 29February 2000 [Table 6]. Of the 207cases, 55 cases (26.6%) wereexcluded, and 152 (73.4%) wereprimary cases included in the study,according to the study criteria.

Case exclusion reasons were examined[Table 6]. The largest number 36(17.4% of total) were secondarycases, which had a member of theirhousehold with diarrhoea orconfirmed cryptosporidiosis, in the14 days prior to the case illness. Sixcases (2.9%) had travelled abroad inthe two weeks prior to illness. Fourcases (2 %) could be defined as non-responders, if the case exclusionreasons of the non-responders, refusalto participate and notinterviewed/social reasons werecombined. Three cases had travelledoutside the study area for more thanseven days. (These were revalidatedin 2002 and adjusted for theintervention study). There was onlyone visitor to the area. Three casesdid not fulfil the study criteria; onewas a resident outside the study area,another had a dual infection and thethird had no diarrhoea.

Comparison of the case exclusionreasons for the local authorities ofAllerdale and Copeland did not showany marked differences. (Tables 7,8).

The total number of primary casesincluded into the sporadic case-control study was 152 [Table 6].


Case control study : Exclusions

55

Sp

ora

dic

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rid

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ntr

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)0

(0.0

)55

(26.6

)

Tota

l p

rim

ary

case

s31

(77.5

)20

(83.3

)38

(73.1

)61

(68.5

)2

(100.0

)152

(73.4

)

Tota

l ca

ses

rep

ort

ed40

(100.0

)24

(100.0

)52

(100.0

)89

(100.0

)2

(100.0

)207

(100.0

)

* N

ote

fro

m 0

1/0

3/1

996

Def

init

ion

s

Sec

ondar

y =

Cas

e w

her

e a

mem

ber

of

thei

r house

hold

had

dia

rrhoea

or

confi

rmed

Cry

pto

spori

dio

sis

in t

he

14 d

ays

pri

or

to t

he

case

's i

llnes

s

Dual

infe

ctio

n =

Cas

e w

ith c

onfi

rmed

Cry

pto

spori

dio

sis

& a

noth

er p

athogen

cap

able

of

causi

ng g

astr

o-i

nte

stin

al i

llnes

s

Res

iden

ce o

uts

ide

study a

rea

= C

ase

lives

adja

cent

to s

tudy a

rea

and o

nly

iden

tifi

ed a

s outs

ide

study a

rea

at i

nte

rvie

w

Tab

le 6

S

um

mary

of

Case

Excl

usi

on

Rea

son

s fr

om

1 M

arc

h 1

996 t

o 2

9 F

ebru

ary

2000

TO

TA

L

1996(*

)1997

1998

1999

2000

All

excl

usi

ons

are

due

toth

est

ated

even

tin

the

14

day

spri

or

toth

eonse

tof

sym

pto

ms

oth

erth

anfo

rnon

resp

onder

s,re

fusa

lsan

dth

ose

not

inte

rvie

wed

/inte

rvie

wed

pre

vio

usl

y

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

edC

ase

excl

usi

on

rea

son

s

Spor

adic

Cry

ptos

pori

dios

is C

ase

- C

ontr

ol S

tudy

TA

BL

E 6

SU

MM

AR

YO

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FR

OM

1 M

AR

CH

199

6 T

O 2

9 F

EB

RU

AR

Y20

00



56

Sp

ora

dic

Cry

pto

spo

rid

iosi

s C

ase

-Co

ntr

ol

Stu

dy

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

Sec

on

dary

4(2

1.1

)1

(7.7

)3

(10.3

)11

(22.0

)0

(0.0

)19

(17.0

)

Sec

on

dary

& i

nte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Sec

on

dary

& c

on

tact

wit

h c

on

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Con

tact

wit

h a

con

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Bee

n a

bro

ad

0(0

.0)

0(0

.0)

1(3

.4)

2(4

.0)

0(0

.0)

3(2

.7)

Aw

ay g

reate

r th

an

7 d

ays

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.0)

0(0

.0)

1(0

.9)

Vis

itor

to s

tud

y a

rea

0(0

.0)

1(7

.7)

0(0

.0)

0(0

.0)

0(0

.0)

1(0

.9)

Res

iden

ce o

uts

ide

stu

dy a

rea

0(0

.0)

0(0

.0)

1(3

.4)

0(0

.0)

0(0

.0)

1(0

.9)

Non

res

pon

der

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.0)

0(0

.0)

1(0

.9)

Ref

use

d t

o p

art

icip

ate

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.0)

0(0

.0)

1(0

.9)

Not

inte

rvie

wed

/Soci

al

reaso

ns

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Inte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)1

(3.4

)1

(2.0

)0

(0.0

)2

(1.8

)

Du

al

infe

ctio

n0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Du

al

infe

ctio

n a

nd

bee

n a

bro

ad

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

No d

iarr

hoea

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Tota

l ex

clu

ded

case

s4

(21.1

)2

(15.4

)6

(20.7

)17

(34.0

)0

(0.0

)29

(25.9

)

Tota

l p

rim

ary

case

s15

(78.9

)11

(84.6

)23

(79.3

)33

(66.0

)1

(100.0

)83

(74.1

)

Tota

l ca

ses

rep

ort

ed19

(100.0

)13

(100.0

)29

(100.0

)50

(100.0

)1

(100.0

)112

(100.0

)

* N

ote

fro

m 0

1/0

3/1

996

Def

init

ion

s

Sec

ondar

y =

Cas

e w

her

e a

mem

ber

of

thei

r house

hold

had

dia

rrhoea

or

confi

rmed

Cry

pto

spori

dio

sis

in t

he

14 d

ays

pri

or

to t

he

case

's i

llnes

s

Dual

infe

ctio

n =

Cas

e w

ith c

onfi

rmed

Cry

pto

spori

dio

sis

& a

noth

er p

athogen

cap

able

of

causi

ng g

astr

o-i

nte

stin

al i

llnes

s

Res

iden

ce o

uts

ide

study a

rea

= C

ase

lives

adja

cent

to s

tudy a

rea

and o

nly

iden

tifi

ed a

s outs

ide

study a

rea

at i

nte

rvie

w

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

edT

OT

AL

2000

Tab

le 7

S

um

mary

of

Case

Excl

usi

on

Rea

son

s fr

om

1 M

arc

h 1

996 t

o 2

9 F

ebru

ary

2000 (

AL

LE

RD

AL

E)

1996(*

)1997

1998

1999

All

excl

usi

ons

are

due

toth

est

ated

even

tin

the

14

day

spri

or

toth

eonse

tof

sym

pto

ms

oth

erth

anfo

rnon

resp

onder

s,re

fusa

lsan

dth

ose

not

inte

rvie

wed

/inte

rvie

wed

pre

vio

usl

y

Case

excl

usi

on

rea

son

s

Spor

adic

Cry

ptos

pori

dios

is C

ase

- C

ontr

ol S

tudy

TA

BL

E 7

SU

MM

AR

YO

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FR

OM

1 M

AR

CH

199

6 T

O 2

9 F

EB

RU

AR

Y20

00 (

AL

LE

RD

AL

E)



57

Sp

ora

dic

Cry

pto

spo

rid

iosi

s C

ase

-Co

ntr

ol

Stu

dy

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

Sec

on

dary

2(9

.5)

2(1

8.2

)5

(21.7

)8

(20.5

)0

(0.0

)17

(17.9

)

Sec

on

dary

& i

nte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Sec

on

dary

& c

on

tact

wit

h c

on

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Con

tact

wit

h a

con

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Bee

n a

bro

ad

1(4

.8)

0(0

.0)

0(0

.0)

2(5

.1)

0(0

.0)

3(3

.2)

Aw

ay g

reate

r th

an

7 d

ays

1(4

.8)

0(0

.0)

1(4

.3)

0(0

.0)

0(0

.0)

2(2

.1)

Vis

itor

to s

tud

y a

rea

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Res

iden

ce o

uts

ide

stu

dy a

rea

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Non

res

pon

der

1(4

.8)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

1(1

.1)

Ref

use

d t

o p

art

icip

ate

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Not

inte

rvie

wed

/Soci

al

reaso

ns

0(0

.0)

0(0

.0)

1(4

.3)

0(0

.0)

0(0

.0)

1(1

.1)

Inte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Du

al

infe

ctio

n0

(0.0

)0

(0.0

)1

(4.3

)0

(0.0

)0

(0.0

)1

(1.1

)

Du

al

infe

ctio

n a

nd

bee

n a

bro

ad

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

No d

iarr

hoea

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.6)

0(0

.0)

1(1

.1)

Tota

l ex

clu

ded

case

s5

(23.8

)2

(18.2

)8

(34.8

)11

(28.2

)0

(0.0

)26

(27.4

)

Tota

l p

rim

ary

case

s16

(76.2

)9

(81.8

)15

(65.2

)28

(71.8

)1

(100.0

)69

(72.6

)

Tota

l ca

ses

rep

ort

ed21

(100.0

)11

(100.0

)23

(100.0

)39

(100.0

)1

(100.0

)95

(100.0

)

* N

ote

fro

m 0

1/0

3/1

996

Def

init

ion

s

Sec

ondar

y =

Cas

e w

her

e a

mem

ber

of

thei

r house

hold

had

dia

rrhoea

or

confi

rmed

Cry

pto

spori

dio

sis

in t

he

14 d

ays

pri

or

to t

he

case

's i

llnes

s

Dual

infe

ctio

n =

Cas

e w

ith c

onfi

rmed

Cry

pto

spori

dio

sis

& a

noth

er p

athogen

cap

able

of

causi

ng g

astr

o-i

nte

stin

al i

llnes

s

Res

iden

ce o

uts

ide

study a

rea

= C

ase

lives

adja

cent

to s

tudy a

rea

and o

nly

iden

tifi

ed a

s outs

ide

study a

rea

at i

nte

rvie

w

Tab

le 8

S

um

mary

of

Case

Excl

usi

on

Rea

son

s fr

om

1 M

arc

h 1

996 t

o 2

9 F

ebru

ary

2000 (

CO

PE

LA

ND

) TO

TA

L

All

excl

usi

ons

are

due

toth

est

ated

even

tin

the

14

day

spri

or

toth

eonse

tof

sym

pto

ms

oth

erth

anfo

rnon

resp

onder

s,re

fusa

lsan

dth

ose

not

inte

rvie

wed

/inte

rvie

wed

pre

vio

usl

y

Case

excl

usi

on

rea

son

s

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

1996(*

)1997

1998

1999

2000

Spor

adic

Cry

ptos

pori

dios

is C

ase

- C

ontr

ol S

tudy

TA

BL

E 8

SU

MM

AR

YO

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FR

OM

1 M

AR

CH

199

6 T

O 2

9 F

EB

RU

AR

Y20

00 (

CO

PE

LA

ND

)



58

b) Sporadic case-control study: 1March 1996 - 29 February 2000

Controls: exclusions andexclusion reasons (Tables 9, 10)

Tables 9 and 10 show the differentcategories of controls. The ‘notcontacted’ (B) category shows thenumber of controls that were on thelist generated by the computer butwere not used [Table 9]. The RA hadnot contacted the controls, butchecks against names already in theresearch database had beenconducted. Therefore the number ofcontrols in this category mainlyrepresents ‘extra’ controls thatremained on the list, after theachievement of the three requiredcontrols, and some duplicates of casesor controls already in the study. Atotal of 378 controls were in thiscategory [Table 9]. There were nomarked changes between 1996 and1999 in the proportion of controls inthis category. However in late 1999,certain areas such as Millomexperienced difficulty in recruitmentof controls, particularly children, asmany were already in the research.To avoid duplication, additionalcontrols had to be generated by thecomputer, adding another fivecontrols to the original five in the listfor contact.

Reasons why 312 controls werecontacted but not incorporated intothe study, category (A), are listed inTable 10. The main reason was ‘noanswer’; 125 controls (40.1%) werenot present at interview time and didnot respond to follow up. Thirty-fivecontrols (11.2%) made contact tocancel interviews or confirmunavailability at the time. The RA

cancelled 19 interviews foradministrative reasons, havingachieved the required three controls.Twenty- three (7.4%) controls alsorefused to be interviewed. Therewere 27 (8.7%) controls who hadmoved and therefore not resident atthe address provided. Two controlswere residents outside the study area,and the addresses of three controlscould not be found. Of the controlsthat had been interviewed, the largestnumber, 46 (14.7%) were excludedbecause of diarrhoea. A smallernumber, five (1.6%) had travelledabroad, and seven (2.2%) had beeninterviewed previously. Eightcontrols had also travelled outside thestudy area for more than 7 days andwere not used. (These were furthervalidated for the Intervention Studyin June 2002). The reasons forexclusion of three controls were notknown.

The final number of controlsincorporated into the sporadic casecontrol study was 466 controls[Table 9].



59

Primary

cases total

(n) (n)

As % of all

controls in

year

(n)

As % of all

controls in

year

(n)

As % of all

controls in

year

(n)

As % of all

controls in

year

1996 31 96 41% 47 20% 92 39% 235 100%

1997 20 50 45% 23 21% 37 34% 110 100%

1998 38 120 42% 78 27% 89 31% 287 100%

1999 61 197 38% 164 32% 154 30% 515 100%

2000 2 3 33% 0 0% 6 67% 9 100%

Total 152 466 40% 312 27% 378 33% 1156 100%

Definitions

Category A = Controls contacted from list generated, letters sent / visits made / interviews conducted.

See next table (10) for exclusion reasons for category A controls

Category B = Controls in list generated by computer, no contact made either by post, telephone or visits.

Checks made against names held on database.

Cases Controls

Year

Incorporated into

study

Contacted but not

incorporated

(Category A)

Not contacted

(Category B)

Total provided by

NCHA

Sporadic Cryptosporidiosis Case - control study1 March 1996 to 29 February 2000

TABLE 9 CONTROLS GENERATED AND USAGE



60

Sporadic Cryptosporidiosis Case - control study1 March 1996 to 29 February 2000

TABLE 10 CONTROL EXCLUSION REASONS - NUMBER N, (%) CONTACTED BUT NOTINCORPORATED CATEGORY A

Definitions1) No answer = Not present at requested interview time and no response to follow up as per interview protocol.2) Not convenient = Control makes contact to either cancel the requested interview or confirm reasons for being un-available

when RA has visited at the requested time e.g. Control away from home.3) Cancelled = The interview request was cancelled by the RA for administrative reasons e.g. sufficient controls obtained or case

excluded.4) Address not found = Control address could not be found.5) Diarrhoea = Protocol exclusion reason6) Abroad = Travel abroad in the 14 days prior to interview, a protocol exclusion reason.7) Residence outside area = Control address found to be outside study area, a protocol exclusion reason.8) Wrong age = Age of control is not in the same age band as that of the case, a protocol exclusion reason.9) Moved = Control not resident at the address provided.

10) Interviewed prior = Control or a member of their household previously interviewed as a control or case.11) Refused = Declined to be interviewed or give consent after interview.12) Unknown = Reason for exclusion not recorded on the administrative database.13) Outside area >7 days = More than seven nights away from home in the 14 days before interview.

n (%)

1) No Answer 125 40.1%

2) Not convenient 35 11.2%

3) Cancelled 19 6.1%

4) Address not found 3 1.0%

5) Diarrhoea 46 14.7%

6) Abroad 5 1.6%

7) Residence outside area 2 0.6%

8) Wrong age 9 2.9%

9) Moved 27 8.7%

10) Interviewed prior 7 2.2%

11) Refused 23 7.4%

12) Unknown 3 1.0%

13) Outside area > 7 days 8 2.6%

Total 312 100.0%

Exclusion reasonNumber of controls (%)

N.B. Due to rounding of individual %, the sum of these may not equal 100%


SPORADIC CRYPTOSPORIDIUM IN WEST CUMBRIA : A Case-Control Study

STATISTICS REPORT - NEVILLE VERLANDER AND MARK REACHER

IntroductionA case-control study was set up in West Cumbria in March 1996 following local increases insporadic Cryptosporidium cases. Cases were those individuals satisfying the following criteria:diarrhoea, Cryptosporidium (and no other pathogen) identified in the stool sample and onset ofsymptoms during the study period. Cases were also required to have not had any known contactwith a case of cryptosporidiosis in the two weeks prior to onset of illness and no householdmember was to have had symptoms of diarrhoea in the two weeks prior to onset of illness.Controls were those individuals with no diarrhoea in the two weeks before interview. Both casesand controls had to be resident in the Copeland and Allerdale local authority areas and were notto have travelled abroad in the two weeks prior to illness or interview, respectively. Theobjective of the study was to determine how the incidence of cases was associated with a numberof risk factors. In particular, the study was designed to investigate whether there was anyevidence of a dose-response relationship between Cryptosporidium infection and theconsumption of unboiled mains water. This report considers data collected to 29 February2000. Three controls, frequency matched on age group (0-5 yrs, 6-15 yrs, 16+ yrs) andpostcode, were randomly selected for each case.

A total of 58 individuals were excluded for violating one or more of the case or control definitions,resulting in 152 cases and 466 controls being considered in the analysis.

Data ManipulationThe manipulations that were performed on the data are mentioned here. Unsure responses werecoded as missing. Questions which had no responses had their sub-questions also set to no. Forinstance, if the respondent had no contact with a farm animal then that person did not feed a farmanimal either. The exception to this rule concerned hand washing: if the respondent did not feeda farm animal, then a separate category for hand washing response was made, namely ‘no contactwith farm animal.’ When there were multiple choices to a particular question, if the box was leftunticked the response was assumed to be no. For instance, it was assumed did not feed pet tinnedfood if the corresponding box was not ticked. If there was no response or the response was unsureregarding contact with slurry, the frequency and type of slurry contact was set to missing. Likewisefor farm, farm animal and animal contact. Individuals who did not drink water were assigned asdrinking 0 pints of water at home and at work and included in the <1/4 pints category in the singlevariable analysis. Total water consumed was found by adding the pints drunk at home and at workand then categorised for the single variable analysis as above. For the multivariable analysis, totalpints of water drunk used the uncategorised values and was treated as a continuous variable.Likewise for soft drinks and pasteurised milk. Question 27 in the questionnaire asked aboutconsumption of lettuce, tomatoes, coleslaw, mixed salad, raw sausages, other uncooked meats,fresh raw vegetables, raw cheese (locally produced and other), yoghurt, ice cream and cream. Each of these foods had four possible categories of, not at all, 1-2 times, 3-7 times and most days,apart from not sure. The first four categories were collapsed to yes and no for analysis.


Statistics Report : Case-Control Study

62

MethodologyEach potential risk factor has been considered singly by way of Odds Ratios (and 95% ConfidenceIntervals) and continuity corrected Chi-square tests or Fisher’s Exact Test where the data are sparse.Dose-response was investigated using Chi-square Tests for Trends. Two sets of analyses wereperformed, one using the whole data set and the other excluding individuals whose householdsreceive a mixed water supply. This involved 51 controls and 11 cases. The results for these two setsof single variable analysis are shown in Appendix A and B, respectively.

Variables with a positive association with illness reaching a 20% significance level were deemedsignificant and included in a Logistic Regression model. Pasteurised milk and hand washing wereincluded in a regression model if they reached 20% significance even if they were protectivefactors, as this is highly plausible. Terms were assessed by comparison of nested models usingLikelihood Ratio Tests. Variables were removed from models if their corresponding p value was 0.3or greater, with the most insignificant ones being removed first. The variables for age, sex andwater supply zone were included and retained in the multivariable models regardless of their singleand multivariable significance. Analyses were done using the statistical software packages Epi-Infoand GLIM.



63

There were a total of 42 cases within the Ennerdale region, 56 within the Crummock region and54 within other regions.

Table 2 shows the age and sex distribution among the water sources.

TABLE 1 AGE AND WATER SOURCE DISTRIBUTION OFTHOSE RECRUITED TO THE STUDY

Cases Controls

AGE n % n %0-5 86 57 273 596-15 47 31 136 2916+ 19 12 57 12

WATER SOURCECrummock 56 37 152 33Ennerdale 42 28 144 31Crummock & Ennerdale 98 64 296 64Other 54 35 170 36

TOTAL 152 100 466 100

TABLE 2 AGE AND SEX DISTRIBUTION AMONG THE WATER SOURCES OF THOSERECRUITED TO THE STUDY

Crummock Ennerdale Crummock Other TOTAL& Ennerdale

Sex Sex Sex SexAge M F M F M F M F

0-5 56 43 72 58 128 101 59 71 359

6-15 40 37 23 23 63 60 36 24 183

16+ 11 21 6 4 17 25 15 19 76

TOTAL 107 101 101 85 208 186 110 114 618

ResultsDescriptive StatisticsThe study involved data collected from 152 cases and 466 controls, of whom 82(54%) cases and236(51%) controls were male. Three hundred and thirty two (59%) of the subjects were aged 5or under, only 64(11%) aged 16 years or over. The age distribution was similar for the cases andcontrols determined by the sampling methods. The mean and median age of the cases were 8 and4 years, respectively, and ranged from 0 to 55 years of age. Table 1 shows the age and water sourcedistribution. The median age was 5 years and ranged from 0 to 83 years of age. The water zonesof Crummock North and Crummock South were amalgamated to form the water source labelledCrummock and the water source of Ennerdale comprised the water zones of Ennerdale North andEnnerdale South. The water zones of Private, Quarry Hill, Fellside, Hayknott, Hausegill,Underscar, Bridge End, Millom and Mixed were amalgamated to form the water source labelledOther. The sex distribution is shown in Appendix A.



64

Figure 1 shows the number of cases per month for all water sources and also for each watersource.

0

5

10

15

20

Mar-96 Mar-97 Mar-98 Mar-99 Mar-00

Month

Nu

mb

er

of

cases

All zones Crummock Ennerdale Other

Table 3 shows the calculations to produce yearly rates per 100,000 by averaging thepopulations in each water source over the four years 1996-1999.

FIGURE 1. PRIMARY CASES RECRUITED TO THE STUDY BY WATER SUPPLY ZONE

TABLE 3. CRYPTOSPORIDIUM INFECTION RATE PER YEAR PER 100,000 BY WATER SOURCE

Water Source Estimate of yearly Population Rate per yearnumber of cases per 100,000

Crummock 14.0 58,295 24.0

Ennerdale 10.5 47,780 22.0

Crummock & Ennerdale 24.0 106,075 23.1

Other 13.5 59,699 22.6

The yearly distribution is shown in Table 4 overleaf. These are crude estimates and therefore takeno account of the seasonality of the distribution of Cryptosporidium cases.



65

1A period of March-August inclusive was used rather than the full-year’s data since this data wasavailable for all four years and scaling up would be difficult due to the seasonality of the organism

Thirty seven cases had continuing symptoms at the time of interview and of the remaining, themedian duration of illness was 9 days (range: 2-21). The most common symptoms experienced bythe 152 cases are given in Table 5 below:

Year Water Source Number of Cases Population Rate for 6 monthsestimated within 6 per 100,000

month period 1

1996 Crummock 8 57,120 14.0Ennerdale 10 47,480 21.1Crummock& Ennerdale 18 104,600 17.2Other 7 60,015 11.7




TABLE 5 CASE SYMPTOMS OF THOSE RECRUITED TO THE STUDY

Symptom N %

Diarrhoea 152 100Abdominal Pain 110 72Vomiting 94 62Fever 69 45Loss of Appetite 68 45Weight Loss 56 37

TABLE 6 AGE AND SEX DISTRIBUTION OF HOSPITALISED CASES RECRUITED

TO THE STUDY

SexAge Male Female

0-5 14 5

6-15 2 2

16+ 0 0

Twenty three (15%) of the cases were admitted to hospital due to their illness. The ages ofhospitalised cases ranged from 0 to 14 years with mean and median age of 3.7 and 2 years,respectively. Table 6 shows the age and sex distribution of hospitalised cases.

TABLE 4. YEARLY DISTRIBUTION OF CRYPTOSPORIDIUM INFECTION BY WATER SOURCE



66

Multivariable analysis

An initial multivariable model was fitted which included all the significant variables detailing thefrequency and type of contact with farms, farm animals and slurry and total usual dailyconsumption of cold unboiled tap water (Table 7).

A second model was fitted using usual daily consumption of cold unboiled tap water at homeinstead of total usual daily consumption of cold unboiled tap water (Table 8).

A third model fitted using total usual daily consumption of cold unboiled tap and excludingsubjects served by mixed water supplies (Table 9)

All three models showed that usual consumption of cold unboiled tap water was a highlysignificant risk factor for sporadic cryptosporidiosis. Furthermore, there was no difference in riskbetween the different water supply zones .

In the first model (Table 7) the risk for total usual daily consumption of cold unboiled tap waterincreased by 40 % [ Odds ratio 1.40 (1.14, 1,71) p for trend =0.001] for each pint of waterconsumed per day. (Table 7) The only other significant association was with short visits to farms[Odds ratio 2.02 (1.04, 3.90) p = 0.04] with a borderline increase in risk with feeding pets rawvegetables. [Odds ratio 2.11 (0.98, 4.56) p = 0.06] The results were virtually the same if usualconsumption of unboiled tap water at home was used instead of usual total consumption ofunboiled tap water (Table 8)

In the third model (Table 9), excluding individuals served by mixed public water supplies, madeno substantive difference to the risk estimate of usual total consumption of cold unboiled tapwater [Odds ratio 1.36 (1.07,1.73) p=0.01 for trend] per pint consumed per day. A positiveassociation was also apparent for frequency of farm contact (p for trend = 0.02). A protectiveassociation was suggested for consumption of pasteurised milk [Odds ratio 0.55 (0.33, 0.91)p=0.02 for trend] per pint per day. An apparent protective effect of hand washing associated withanimal contact should be interpreted with caution as individuals with no animal contact were usedas one of the groups in the test for trend.

The important messages from the final models are that the risk of cryptosporidiosis increased by40% with each pint of unboiled tap water usually consumed each day; and that this risk wassimilar for all water supplies to people’s homes.



67

Adjusted Odds Ratio 95% Confidence Interval p value

Water Zone Private 0.004 0, 203.4 0.71Quarry Hill 1.36 0.61, 3.05

Fellside 0.002 0,Hayknott 0.91 0.17, 4.97Hausegill 1.29 0.25, 6.64

Crummock North 1.00Crummock South 1.28 0.61, 2.67

Underscar 1.83 0.16, 20.37Ennerdale North 1.004 0.54, 1.88Ennerdale South 0.91 0.39, 2.11

Bridgend n.e. n.e.Millom 1.06 0.52, 2.18Mixed 0.77 0.34, 1.77

Sex Male 1.10 0.73, 1.67 0.64Female 1.00

Age 0.99 per year 0.97, 1.01 0.29

Total cold tap water consumption 1.40 per pint 1.14, 1.71 0.001*

Other Cheese Y 1.49 0.91, 2.43 0.10N 1.00

Feed pet biscuits Y 1.77 0.94, 3.33 0.08N 1.00

Feed pet raw vegetable Y 2.11 0.98, 4.56 0.06N 1.00

Contact with a cow farm Y 1.67 0.73, 3.82 0.23N 1.00

Other farm contact Y 1.96 0.79, 4.88 0.15N 1.00

Short visit at a farm Y 2.02 1.04, 3.90 0.04*N 1.00

n.e. not estimable * significant at 5% level

8

TABLE 7 MULTIVARIABLE MODEL: USUAL TOTAL DAILY CONSUMPTION OF COLD UNBOILED TAP WATER



68

TABLE 8 MULTIVARIABLE MODEL: USUAL DAILY CONSUMPTION OFCOLD UNBOILED TAP WATER AT HOME


Water Zone Private 0.004 0, 3407 0.86Quarry Hill 1.36 0.61, 3.05

Fellside 0.002 0,Hayknott 0.89 0.16, 4.85Hausegill 1.37 0.26, 7.11



Bridgend n.e. n.e.Millom 1.04 0.51, 2.13Mixed 0.81 0.35, 1.85

Sex Male 1.14 0.75, 1.73 0.54Female 1.00

Age 0.99 per year 0.97, 1.01 0.31

Home cold tap water consumption 1.40 per pint 1.13, 1.74 0.003*

Other Cheese Y 1.56 0.95, 2.56 0.07N 1.00


Feed pet raw vegetable Y 2.22 1.02, 4.86 0.05*N 1.00

Contact with a cow farm Y 1.68 0.73, 3.89 0.23N 1.00


Short visit at a farm Y 2.04 1.05, 3.96 0.04*N 1.00


8



69

TABLE 9 MULTIVARIABLE MODEL: USING TOTAL CONSUMPTION OF COLD UNBOILED TAP WATER

EXCLUDING SUBJECTS SERVED BY MIXED SUPPLIES


Water Zone Private 0.0005 0, 25340 0.28Quarry Hill 1.31 0.51, 3.36

Fellside 0.001 0,Hayknott 0.001 0,Hausegill 0.76 0.09, 6.47



Bridgend n.e. n.e.Millom 1.22 0.56, 2.64

Sex Male 1.53 0.91, 2.58 0.11Female 1.00

Age 0.99 per year 0.96, 1.01 0.28

Total cold tap water consumption 1.36 per pint 1.07, 1.73 0.01*

Other Cheese Y 1.49 0.82, 2.69 0.18N 1.00

Frequency of farm contact 1.19 1.02, 1.39 0.02*

Frequency of farmanimal contact 0.90 0.80, 1.01 0.05*

Feed pet left overs Y 2.68 0.54, 13.28 0.22N 1.00


Feed pet raw vegetable Y 2.18 0.91, 5.22 0.09N 1.00


Pints of pasteurised milk 0.55 per pint 0.33, 0.91 0.02*

Hand washing carried out Y 0.05 0.004, 0.74 0.01*N 1.00

No contact 0.03 0.002, 0.46with farm animal


88



70

APPENDIX A SINGLE VARIABLE ANALYSIS (X2 TEST OR FISHER�S EXACT TEST) - ALL DATA

Cases Controls Odds Ratio 95% CIs p-value

Sex M 82 236 1.14 0.78,1.68 0.539

F 70 230 1.00

Contact with play group Y 61 164 1.27 0.84,1.90 0.269

N 82 279 1.00

Contact with anyone Y 25 63 1.28 0.75, 2.20 0.403with Diarrhoea N 123 398 1.00

Nights away from home Y 49 163 0.88 0.59, 1.33 0.603

N 103 303 1.00

Water supply Mains 150 456 1.64 0.33,11.14 0.7392

Private 2 10 1.00

Mains disrupted Y 8 14 1.79 0.67, 4.70 0.294

N 143 448 1.00

Water discoloration Y 14 33 1.41 0.69, 2.84 0.398

N 130 431 1.00

Cold tap water Y 136 373 2.12 1.16, 3.91 0.012*

N 16 93 1.00

Cold tap water at home <1Ú4 pints 23 106 1.00 0.0051*1Ú4 - 1 65 218 1.37 0.79, 2.42

>1 - 2 40 96 1.92 1.03, 3.59

>2 + 21 40 2.42 1.14, 5.13

Cold tap water at <1Ú4 pints 83 273 1.00 0.4951

work/school 1Ú4 - 1 39 110 1.17 0.73, 1.85

>1+ 2 5 1.32 0.17, 7.82

Total cold tap water <1Ú4 pints 19 108 1.00 0.0171*1Ú4 - 1 58 175 1.88 1.03, 3.47

>1 - 2 45 121 2.11 1.12, 4.01

>2 + 28 62 2.57 1.26, 5.24

Drink outside Y 13 31 1.29 0.62, 2.67 0.573Copeland/Allerdale area N 137 422 1.00

Ice Y 29 106 0.83 0.51, 1.36 0.514

N 116 354 1.00

Ice at home Y 11 57 0.56 0.27, 1.15 0.119*

N 141 409 1.00

Bottled water Y 16 36 1.43 0.73, 2.79 0.323

N 133 429 1.00

Soft drinks Y 87 283 0.86 0.58, 1.27 0.467

N 64 178 1.00

Pints of soft drink <1Ú4 66 181 1.00 0.3581

1Ú4 - 3Ú4 36 110 0.90 0.55, 1.47

1 - 13Ú4 31 103 0.83 0.49, 1.39

2 + 11 40 0.75 0.34, 1.63

Swimming Y 44 141 0.94 0.61, 1.44 0.838

N 108 325 1.00

Water sports Y 2 18 0.33 0.05, 1.53 0.1852*

N 150 448 1.00

Paddling Y 22 57 1.23 0.70, 2.17 0.531

N 128 408 1.00

Other contact with water Y 16 39 1.29 0.66, 2.49 0.516

N 133 418 1.00

1 Chi-Squared Test for Trend 2 Fisher's Exact Test * significant at 20% level



71


Lettuce Y 36 166 0.58 0.37, 0.90 0.013*

N 112 298 1.00

Tomatoes Y 42 170 0.65 0.43, 1.00 0.048*

N 110 291 1.00

Coleslaw Y 26 93 0.85 0.51, 1.41 0.572

N 122 369 1.00

Mixed salad Y 25 123 0.56 0.33, 0.92 0.020*

N 124 339 1.00

Raw sausages Y 6 12 1.56 0.51, 4.61 0.4062

N 145 452 1.00

Other raw meat Y 8 13 1.93 0.71, 5.14 0.233

N 144 451 1.00

Fresh raw vegetables Y 47 177 0.76 0.50, 1.16 0.216

N 100 288 1.00

Local cheese Y 5 8 1.94 0.54, 6.71 0.3252

N 144 446 1.00

Other cheese Y 113 322 1.43 0.91, 2.27 0.124*

N 34 139 1.00

Yoghurt Y 113 346 1.03 0.66, 1.63 0.968

N 37 117 1.00

Ice cream Y 98 338 0.68 0.45, 1.04 0.072*

N 53 125 1.00

Cream Y 18 95 0.53 0.30, 0.95 0.029*

N 131 369 1.00

Pasteurised milk Y 134 396 1.30 0.72, 2.36 0.431

N 18 69 1.00

Pints of pasteurised milk <1Ú4 19 71 1.00 0.2211

1Ú4 - 3Ú4 66 153 1.61 0.87, 3.01

1+ 56 202 1.04 0.56, 1.94

Unpasteurised milk Y 9 22 1.28 0.53, 3.02 0.699

N 142 443 1.00

Contact with domestic pets Y 98 293 1.08 0.72, 1.62 0.770

N 53 171 1.00

Any pet with diarrhoea Y 6 23 0.78 0.27, 2.12 0.763

N 85 254 1.00

Contact with slurry Y 16 28 2.00 0.99, 4.02 0.052*

N 116 406 1.00

Contact with farms Y 59 108 2.11 1.40, 3.20 <0.001*

N 91 352 1.00

Contact with farm animals Y 53 92 2.23 1.45, 3.43 <0.001*

N 94 364 1.00

Feed animal4 Y 23 45 1.74 0.97, 3.12 0.061*

N 116 396 1.00

Other animal contact Y 75 248 0.84 0.54, 1.30 0.475

N 51 142 1.00

Faecal contact4 Y 13 17 3.04 1.33, 6.94 0.006*

N 89 354 1.00

Sewerage system Mains 130 411 0.73 0.41, 1.31 0.322

Other3 22 51 1.00

1 Chi-Squared Test for Trend 2 Fisher's Exact Test 3 37 septic tanks and 1 chemical toilet (case)

4 Not on questionnaire for first 4 months of study (88 questionnaires affected)

* significant at 20% level



72


Feed your pet Raw Meat Y 0 2 0.00 0.00, 12.74 1.0002

N 152 464 1.00

Feed your pet Tinned Meat Y 42 126 1.03 0.67, 1.59 0.970

N 110 340 1.00

Feed your pet Pellets Y 2 6 1.02 0.00, 5.73 1.0002

N 150 460 1.00

Feed your pet Biscuits Y 21 39 1.76 0.95, 3.21 0.070*

N 131 427 1.00

Feed your pet Left overs Y 6 5 3.79 1.00, 14.69 0.0312*

N 146 461 1.00

Feed your pet Raw veg Y 13 20 2.09 0.95, 4.56 0.069*

N 139 446

Feed your pet Other food Y 44 127 1.09 0.71, 1.67 0.763

N 108 339 1.00

Eat Food within 1-2 hours Y 32 41 3.11 1.79, 5.38 <0.001*of contact with farm animal N 96 382 1.00

Hand washing carried out Y 27 39 1.00 <0.001*

N 5 4 1.81 0.44, 7.35

No Contact 94 364 0.37 0.22, 0.64with farm animal

Walk past slurry Y 5 10 1.72 0.50, 5.64 0.3512

N 123 422 1.00

Close to slurry (in field) Y 6 9 2.31 0.71, 7.34 0.1222*

N 122 423 1.00

Other contact with slurry Y 1 7 0.48 0.02, 3.95 0.6892

N 127 425 1.00

Frequency of contact 0 116 406 1.00 0.2831

with slurry 1 6 9 2.33 0.72, 7.34

2 3 4 2.63 0.46, 14.09

3 2 4 1.75 0.22, 11.25

>3 2 7 1.00 0.10, 5.35

Frequency of farm contact 0 91 352 1.00 0.0031*

1-5 44 82 2.08 1.32, 3.27

6-10 3 2 5.80 0.78, 50.38

>10 8 11 2.81 1.00, 7.81




73


Any contact with Y 13 18 2.38 1.06, 5.31 0.033*dairy farm N 127 418 1.00

Any contact with cow farm Y 15 29 1.68 0.83, 3.40 0.164*

N 125 407 1.00

Any contact with Y 10 20 1.60 0.67, 3.73 0.334mixed farm N 130 416 1.00

Any contact with Y 15 19 2.63 1.22, 5.66 0.010*other farm N 125 417 1.00

Any short visit at a farm Y 40 57 2.56 1.57, 4.17 <0.001*

N 107 391 1.00

Any overnight stay Y 1 5 0.61 0.03, 5.45 1.0002

at a farm N 146 443 1.00

Any other farm contact Y 17 41 1.30 0.68, 2.46 0.487

N 130 407 1.00

Stroke any farm animal Y 29 49 2.01 1.17, 3.42 0.009*

N 123 417 1.00

Feed any farm animal Y 16 32 1.60 0.80, 3.14 0.197*

N 136 434 1.00

Any other contact Y 28 35 2.78 1.57, 4.93 <0.001*with a farm animal N 124 431 1.00

Frequency of farm 0 94 364 1.00 0.0511*animal contact 1-20 38 68 2.16 1.34, 3.50

>20 4 5 3.10 0.68, 13.60

Local Authority Allerdale 83 248 1.06 0.72, 1.55 0.838

Copeland 69 218 1.00

Water Supply Zone Private 2 9 0.62 0.13, 3.00 0.946

Quarry Hill 16 41 1.09 0.55, 2.16

Fellside 0 1 0.03 0, 3674

Hayknott 2 6 0.93 0.18, 4.80

Hausegill 3 5 1.67 0.38, 7.33

Crummock N 37 103 1.00

Crummock S 19 49 1.08 0.56, 2.07

Underscar 1 3 0.93 0.09, 9.18

Ennerdale N 29 101 0.80 0.46, 1.40

Ennerdale S 13 43 0.84 0.41, 1.74

Bridgend 0 0 n.e. n.e.

Millom 19 54 0.98 0.51, 1.86

Mixed 11 51 0.60 0.28, 1.27

1 Chi-Squared Test for Trend 2 Fisher's Exact Test n.e. not estimable




74

APPENDIX B - SINGLE VARIABLE ANALYSIS (X2 TEST OR FISHER'S EXACT TEST) - EXCLUDING MIXED WATER SUPPLY


Sex M 79 210 1.24 0.83, 1.87 0.309

F 62 205 1.00

Contact with play group Y 57 146 1.29 0.84, 1.97 0.259

N 75 247 1.00

Contact with anyone with Y 23 58 1.22 0.69, 2.15 0.539Diarrhoea N 114 352 1.00

Nights away from home Y 45 146 0.86 0.56, 1.33 0.547

N 96 269 1.00

Water supply Mains 139 406 1.54 0.30, 10.59 0.7382

Private 2 9 1.00

Mains disrupted Y 8 12 2.02 0.73, 5.48 0.206

N 132 399 1.00

Water discoloration Y 13 29 1.41 0.67, 2.95 0.422

N 122 384 1.00

Cold tap water Y 126 335 2.01 1.07, 3.80 0.026*

N 15 80 1.00

Cold tap water at home <1Ú4 pints 20 93 1.00 0.0041*1Ú4 - 1 59 197 1.39 0.77, 2.55

>1 - 2 40 85 2.19 1.14, 4.23

>2 + 19 36 2.45 1.10, 5.47

Cold tap water at <1Ú4 pints 75 245 1.00 0.4061

work/school 1Ú4 - 1 37 97 1.25 0.77, 2.02

>1+ 2 5 1.31 0.12, 8.17

Total cold tap water <1Ú4 pints 16 93 1.00 0.0201*1Ú4 - 1 53 157 1.96 1.02, 3.81

>1 - 2 45 109 2.40 1.22, 4.76

>2 + 25 56 2.59 1.21, 5.61

Drink outside Y 12 31 1.13 0.53, 2.39 0.869Copeland/Allerdale area N 127 371 1.00

Ice Y 25 95 0.76 0.45, 1.28 0.324

N 109 314 1.00

Ice at home Y 11 51 0.60 0.29, 1.25 0.191*

N 130 364 1.00

Bottled water Y 13 33 1.20 0.58, 2.47 0.722

N 125 381 1.00

Soft drinks Y 80 250 0.85 0.57, 1.29 0.484

N 60 160 1.00

Pints of soft drink <1Ú4 61 163 1.00 0.2401

1Ú4 - 3Ú4 36 95 1.01 0.61, 1.69

1 - 13Ú4 27 94 0.77 0.44, 1.33

2 + 9 33 0.73 0.30, 1.70

Swimming Y 42 124 1.00 0.64, 1.55 0.932

N 99 291 1.00

Water sports Y 2 16 0.36 0.06, 1.67 0.2682

N 139 399 1.00

Paddling Y 21 51 1.26 0.70, 2.26 0.503

N 119 363 1.00

Other contact with water Y 16 37 1.32 0.67, 2.56 0.484

N 122 371 1.00




75


Lettuce Y 32 151 0.53 0.33, 0.85 0.006*

N 105 262 1.00

Tomatoes Y 39 152 0.65 0.42, 1.01 0.054*

N 102 258 1.00

Coleslaw Y 24 83 0.84 0.49, 1.43 0.576

N 113 328 1.00

Mixed salad Y 23 112 0.53 0.31, 0.91 0.017*

N 115 299 1.00

Raw sausages Y 5 9 1.66 0.47, 5.60 0.3592

N 135 404 1.00

Other raw meat Y 8 11 2.20 0.78, 6.09 0.1072*

N 133 402 1.00

Fresh raw vegetables Y 42 161 0.70 0.45, 1.09 0.115*

N 94 253 1.00

Local cheese Y 5 8 1.86 0.51, 6.45 0.3322

N 133 395 1.00

Other cheese Y 105 292 1.37 0.85, 2.22 0.212

N 31 118 1.00

Yoghurt Y 105 310 1.02 0.63, 1.64 0.965

N 34 102 1.00

Ice cream Y 90 296 0.71 0.46, 1.09 0.114*

N 50 116 1.00

Cream Y 18 86 0.57 0.31, 1.02 0.058*

N 120 327 1.00

Pasteurised milk Y 124 357 1.16 0.63, 2.18 0.709

N 17 57 1.00

Pints of pasteurised milk <1Ú4 18 59 1.00 0.082 1*1Ú4 - 3Ú4 63 136 1.52 0.80, 2.92

1+ 49 181 0.89 0.46, 1.72

Unpasteurised milk Y 9 19 1.43 0.58, 3.46 0.525

N 131 395 1.00

Contact with domestic pets Y 92 263 1.09 0.71, 1.68 0.740

N 48 150 1.00

Any pet with diarrhoea Y 6 20 0.87 0.30, 2.41 0.949

N 79 228 1.00

Contact with slurry Y 15 23 2.18 1.03, 4.57 0.038*

N 108 361 1.00

Contact with farms Y 56 97 2.17 1.41, 3.35 <0.001*

N 83 312 1.00

Contact with farm animals Y 48 80 2.19 1.39, 3.45 <0.001*

N 89 325 1.00

Feed animal4 Y 21 37 1.84 0.99, 3.41 0.054*

N 109 353 1.00

Other animal contact Y 72 224 0.85 0.54, 1.34 0.514

N 46 121 1.00

Faecal contact4 Y 13 17 2.97 1.29, 6.80 0.007*

N 82 318 1.00

Sewerage system Mains 120 369 0.68 0.37, 1.25 0.230

Other3 21 44 1.00

1 Chi-Squared Test for Trend 2 Fisher's Exact Test 3 37 septic tanks and 1 chemical toilet (case)

4 Not on questionnaire for first 4 months of study (88 questionnaires affected)




76


Feed your pet Raw Meat Y 0 2 0.00 0.00, 12.24 1.0002

N 141 413 1.00

Feed your pet Tinned Meat Y 39 110 1.06 0.67, 1.67 0.875

N 102 305 1.00

Feed your pet Pellets Y 2 6 0.98 0.00, 5.50 1.0002

N 139 409 1.00

Feed your pet Biscuits Y 20 34 1.85 0.98, 3.48 0.056*

N 121 381 1.00

Feed your pet Left overs Y 5 4 3.78 0.86, 17.19 0.0502*

N 136 411 1.00

Feed your pet Raw veg Y 13 18 2.24 1.00, 5.00 0.049*

N 128 397

Feed your pet Other food Y 42 112 1.15 0.73, 1.79 0.594

N 99 303 1.00

Eat Food within 1-2 hours Y 29 33 3.34 1.85, 6.03 <0.001*of contact with farm animal N 90 342 1.00

Hand washing carried out Y 24 33 1.00 <0.001*

N 5 3 2.29 0.51, 10.53

No Contact 89 325 0.38 0.21, 0.67with farm animal

Walk past slurry Y 5 8 2.06 0.56, 7.17 0.2002*

N 114 375 1.00

Close to slurry (in field) Y 5 8 2.06 0.56, 7.17 0.2002*

N 114 375 1.00

Other contact with slurry Y 1 6 0.53 0.02, 4.57 1.0002

N 118 377 1.00

Frequency of contact 0 108 361 1.00 0.2091

with slurry 1 6 7 2.87 0.78, 10.17

2 2 4 1.67 0.15, 11.83

3 2 2 3.34 0.24, 46.47

>3 2 6 1.11 0.11, 6.35

Frequency of farm contact 0 83 312 1.00 1.00 <0.0011*

1-5 41 75 2.05 1.21, 3.31

6-10 3 2 5.64 0.63, 68.14

>10 8 8 3.76 1.41, 4.03

1 Chi-Squared Test for Trend 2 Fisher's Exact Test




77


Any contact with Y 13 15 2.75 1.18, 6.37 0.015*dairy farm N 117 371 1.00

Any contact with Y 15 23 2.06 0.98, 4.31 0.056*cow farm N 115 363 1.00

Any contact with Y 9 20 1.36 0.55, 3.28 0.599mixed farm N 121 366 1.00

Any contact with Y 14 18 2.47 1.11, 5.44 0.022*other farm N 116 368 1.00

Any short visit Y 38 55 2.41 1.46, 3.98 <0.001*at a farm N 98 342 1.00

Any overnight stay Y 1 5 0.58 0.03, 5.22 1.0002

at a farm N 135 392 1.00

Any other farm contact Y 16 32 1.52 0.76, 3.01 0.259

N 120 365 1.00

Stroke any farm animal Y 27 40 2.22 1.26, 3.92 0.004*

N 114 375 1.00

Feed any farm animal Y 15 25 1.86 0.89, 3.83 0.100*

N 126 390 1.00

Any other contact Y 23 31 2.41 1.30, 4.49 0.004*with a farm animal N 118 384 1.00

Frequency of 0 89 325 1.00 0.0141*farm animal contact 1-20 34 59 2.10 1.26, 3.50

>20 4 3 4.87 0.80, 33.68

Local Authority Allerdale 80 218 1.19 0.79, 1.78 0.443

Copeland 61 197 1.00

Water Supply Zone Private 2 9 0.62 0.13, 3.00 0.986

Quarry Hill 16 41 1.09 0.55, 2.16

Fellside 0 1 0.03 0, 3674

Hayknott 2 6 0.93 0.18, 4.80

Hausegill 3 5 1.67 0.38, 7.33

Crummock N 37 103 1.00

Crummock S 19 49 1.08 0.56, 2.07

Underscar 1 3 0.93 0.09, 9.18

Ennerdale N 29 101 0.80 0.46, 1.40

Ennerdale S 13 43 0.84 0.41, 1.74

Bridgend 0 0 n.e. n.e.

Millom 19 54 0.98 0.51, 1.86

1 Chi-Squared Test for Trend 2 Fisher's Exact Test n.e. not estimable * significant at 20% level


Intervention Study Exclusions

78

C i)Cryptosporidiosis InterventionStudy:Pre intervention period : 1 March 1996- 29 February 2000Post intervention period : 1 August2000 - 31 August 2002

a) Laboratory reported cases -Exclusions and exclusionreasons in the pre and postintervention periods

Tables 11-13 show the laboratoryreported cases of the intervention study.The cases that occurred in the filter-commissioning period between 1 March2000 and 31 July 2000 are not shownin the tables. The number of cases inthe pre intervention period differedslightly from that shown in the sporadiccase control study; this was the result offurther validation of all cases in June2002. Cases in the ‘away for 7 days’category of the sporadic case controlstudy were redefined into othercategories or included into the study as‘away from home in U.K.’ for statisticalanalysis.

The total number of laboratory reportedcases in the pre-intervention period was207 with 54 cases excluded and 153primary cases included in the study[Table 11]. The post interventionperiod featured a total of only 31laboratory reported cases with 13 casesexcluded and 18 primary cases includedin the study. Comparisons of theproportion of included and excludedcases in the two time periods show26.1% excluded and 73.9% included inthe pre intervention period contrastingwith 41.9% excluded and 58.1%included in the post-interventionperiod. This represented a marked

decrease in the proportion ofprimary/included cases and the increasein proportion of excluded cases in thepost intervention period. The decreasein total cases in the post interventionperiod began in year 2000 andcontinued into year 2001 and 2002.Year 2001 was the year of the Foot andMouth outbreak the effects of whichwere likely to reduce the numbers ofhuman cryptosporidiosis cases duringthat time.

Examination of the proportion ofincluded and excluded cases in Allerdaleand Copeland did not show any markeddifferences in the two local authoritiesin the pre intervention period [Tables12,13]. However in the postintervention period, there was only atotal of 31 reported cases, 22 cases inAllerdale and 9 in Copeland. Thereduction in total cases was moremarked in Copeland than Allerdale.The total number of cases in Allerdalewas 112 in the pre intervention periodand 22 in the post intervention period,a reduction of 80%. In Copeland, therewere 95 cases in the pre interventionperiod and only 9 cases in the postintervention period, representing areduction of 91%. In both localauthorities the main reduction was inthe included primary cases rather thanthe excluded cases.

The reasons for the exclusions of thecases in the pre and post interventionperiod were examined [table 11]. In thepre intervention period, secondary casespredominate as the main reason forexclusion. Thirty-six cases (17.4%)were in this category. Second to this,eight cases (3.9%) had travelled abroad.In contrast, in the post interventionperiod, seven cases who had travelled



79

abroad (22.6%) featured as the largestgroup. Secondary cases, three cases(9.6%), were the second largest group.The proportion of secondary cases inthe post intervention period (9.6%) wasconsiderably lower than in the preintervention period (17.4%).

The number of cases who had travelledabroad was virtually the same in the preand post intervention periods; eightcases in the pre-intervention period andseven in the post intervention period.However, travel abroad cases representedthe larger proportion in the postintervention period, because of thesmaller overall total number of cases inthe post intervention period [Table 11].

Comparison of the combined categoriesof non-responder, refused to participateand not interviewed/social reasonsshows four cases (2%) in the pre-intervention period and only one case(3.4%) in the post intervention period.The proportional difference was againthe result of the difference in the totalnumber of cases (denominators) in thetwo time periods. The combinedoverall non-responder rate for the wholesix and a half years of the studyremained 2% if all five non-respondercases were considered.

The total number of primary cases forinclusion in the study was 153 cases inthe pre intervention period and 18 casesin the post intervention period. Inaddition, there were four primary casesin the commissioning period, featuredin the footnote of the tables [Table 11].The total for the whole period wastherefore 175 primary cases.



80

Cry

pto

spori

dio

sis

Inte

rven

tion

Stu

dy 1

Marc

h 1

996 t

o 3

1 A

ugu

st 2

002

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

Sec

on

dary

6(1

5.0

)3

(12.5

)8

(15.4

)19

(21.3

)0

(0.0

)36

(17.4

)1

(7.1

)0

(0.0

)0

(0.0

)1

(3.2

)

Sec

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dary

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nte

rvie

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pre

vio

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Sec

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dary

& c

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ase

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Con

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ase

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)

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itor

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0(0

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Res

iden

t ou

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0(0

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0(0

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0(0

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Non

res

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1(2

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0(0

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0(0

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Ref

use

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o p

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icip

ate

0(0

.0)

0(0

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0(0

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1(1

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0(0

.0)

1(0

.5)

0(0

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0(0

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0(0

.0)

0(0

.0)

Not

inte

rvie

wed

/Soci

al

reaso

ns

0(0

.0)

0(0

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1(1

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0(0

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0(0

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Inte

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pre

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y0

(0.0

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(0.0

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(1.9

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(1.1

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0(0

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0(0

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No d

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0(0

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0(0

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0(0

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1(1

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0(0

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Tota

l ex

clu

ded

case

s9

(22.5

)4

(16.7

)13

(25.0

)28

(31.5

)0

(0.0

)54

(26.1

)8

(57.1

)4

(40.0

)1

(14.3

)13

(41.9

)

Tota

l p

rim

ary

case

s31

(77.5

)20

(83.3

)39

(75.0

)61

(68.5

)2

(100.0

)153

(73.9

)6

(42.9

)6

(60.0

)6

(85.7

)18

(58.1

)

Tota

l ca

ses

rep

ort

ed40

(100.0

)24

(100.0

)52

(100.0

)89

(100.0

)2

(100.0

)207

(100.0

)14

(100.0

)10

(100.0

)7

(100.0

)31

(100.0

)

N.B

. F

urt

her

vali

dati

on p

erf

orm

ed J

une 2

002. 4 c

ases "

Aw

ay g

reate

r th

an 7

days" r

e-d

efi

ned. 2 t

ravell

ed a

bro

ad a

nd 2

inclu

ded i

n s

tudy

Table

does n

ot

show

the 4

pri

mary

and 7

exclu

ded (

all

secondary

) cases t

hat

occurr

ed i

n t

he f

ilte

r com

mis

sio

nin

g p

eri

od 0

1/0

3/2

000 t

o 3

1/0

7/2

000

Def

init

ion

s

All

exclu

sio

ns are

due t

o t

he s

tate

d e

vent

in t

he 1

4 d

ays p

rior

to t

he o

nset

of

sym

pto

ms o

ther

than f

or

non r

esponders

, re

fusals

and t

hose n

ot

inte

rvie

wed f

or

socia

l re

asons a

nd i

nte

rvie

wed p

revio

usly

Secondary

= C

ase w

here

a m

em

ber

of

their

household

had d

iarr

hoea o

r confi

rmed c

rypto

spori

dio

sis

in t

he 1

4 d

ays p

rior

to t

he c

ase's

ill

ness

Dual

infe

cti

on =

Case w

ith c

onfi

rmed c

rypto

spori

dio

sis

& a

noth

er

path

ogen c

apable

of

causin

g g

astr

o-i

nte

sti

nal

illn

ess

Resid

ence o

uts

ide s

tudy a

rea =

Case l

ives a

dja

cent

to s

tudy a

rea a

nd o

nly

identi

fied a

s o

uts

ide s

tudy a

rea a

t in

terv

iew

Case

excl

usi

on

rea

son

s

Pre

-in

terv

enti

on

(01/0

3/1

996 t

o 2

9/0

2/2

000)

1997

1998

1999

2000

Post

-in

terv

enti

on

(01/0

8/2

000 t

o 3

1/0

8/2

002)

Tab

le 1

1 C

om

pari

son

of

Case

Excl

usi

on

Rea

son

s fo

r th

e P

re &

Post

In

terv

enti

on

Per

iod

s of

the

Stu

dy

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

TO

TA

L

2000

2001

2002

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

TO

TA

L

1996

TA

BL

E 1

1 C

OM

PAR

ISO

N O

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FO

R T

HE

PR

E &

PO

STIN

TE

RV

EN

TIO

N P

ER

IOD

S O

FT

HE

ST

UD

Y

Cry

ptos

pori

dios

is I

nter

vent

ion

Stud

y 1

Mar

ch 1

996

to 3

1 A

ugus

t 20

02



81

Cry

pto

spori

dio

sis

Inte

rven

tion

Stu

dy 1

Marc

h 1

996 t

o 3

1 A

ugu

st 2

002

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

Sec

on

dary

4(2

1.1

)1

(7.7

)3

(10.3

)11

(22.0

)0

(0.0

)19

(17.0

)1

(10.0

)0

(0.0

)0

(0.0

)1

(5.0

)

Sec

on

dary

& i

nte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Sec

on

dary

& c

on

tact

wit

h c

on

firm

ed c

ase

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0(0

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Con

tact

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0(0

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.4)

3(6

.0)

0(0

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.6)

3(3

0.0

)2

(28.6

)0

(0.0

)5

(25.0

)

Vis

itor

to s

tud

y a

rea

0(0

.0)

1(7

.7)

0(0

.0)

0(0

.0)

0(0

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1(0

.9)

0(0

.0)

0(0

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0(0

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Res

iden

t ou

tsid

e st

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y a

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0(0

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0(0

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0(0

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1(0

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0(0

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0(0

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0(0

.0)

0(0

.0)

Non

res

pon

der

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.0)

0(0

.0)

1(0

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0(0

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0(0

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0(0

.0)

0(0

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Ref

use

d t

o p

art

icip

ate

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.0)

0(0

.0)

1(0

.9)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Not

inte

rvie

wed

/Soci

al

reaso

ns

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

1(1

4.3

)0

(0.0

)1

(5.0

)

Inte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)1

(3.4

)1

(2.0

)0

(0.0

)2

(1.8

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Du

al

infe

ctio

n0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

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(0.0

)0

(0.0

)

Du

al

infe

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n a

nd

bee

n a

bro

ad

0(0

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0(0

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0(0

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0(0

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0(0

.0)

0(0

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1(1

0.0

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(0.0

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(0.0

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(5.0

)

No d

iarr

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0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Tota

l ex

clu

ded

case

s4

(21.1

)2

(15.4

)6

(20.7

)17

(34.0

)0

(0.0

)29

(25.9

)7

(70.0

)3

(42.9

)0

(0.0

)10

(50.0

)

Tota

l p

rim

ary

case

s15

(78.9

)11

(84.6

)23

(79.3

)33

(66.0

)1

(100.0

)83

(74.1

)3

(30.0

)4

(57.1

)5

(100.0

)12

(50.0

)

Tota

l ca

ses

rep

ort

ed19

(100.0

)13

(100.0

)29

(100.0

)50

(100.0

)1

(100.0

)112

(100.0

)10

(100.0

)7

(100.0

)5

(100.0

)22

(100.0

)

N.B

. F

urt

her

vali

dati

on p

erf

orm

ed J

une 2

002. 1 c

ase "

Aw

ay g

reate

r th

an 7

days" r

e-d

efi

ned t

o "

Been a

bro

ad"

Table

does n

ot

show

the 3

pri

mary

and 5

exclu

ded c

ases t

hat

occurr

ed i

n t

he f

ilte

r com

mis

sio

nin

g p

eri

od 0

1/0

3/2

000 t

o 3

1/0

7/2

000

Def

init

ion

s

All

exclu

sio

ns are

due t

o t

he s

tate

d e

vent

in t

he 1

4 d

ays p

rior

to t

he o

nset

of

sym

pto

ms o

ther

than f

or

non r

esponders

, re

fusals

and t

hose n

ot

inte

rvie

wed f

or

socia

l re

asons a

nd i

nte

rvie

wed p

revio

usly

Secondary

= C

ase w

here

a m

em

ber

of

their

household

had d

iarr

hoea o

r confi

rmed c

rypto

spori

dio

sis

in t

he 1

4 d

ays p

rior

to t

he c

ase's

ill

ness

Dual

infe

cti

on =

Case w

ith c

onfi

rmed c

rypto

spori

dio

sis

& a

noth

er

path

ogen c

apable

of

causin

g g

astr

o-i

nte

sti

nal

illn

ess

Resid

ence o

uts

ide s

tudy a

rea =

Case l

ives a

dja

cent

to s

tudy a

rea a

nd o

nly

identi

fied a

s o

uts

ide s

tudy a

rea a

t in

terv

iew

Tab

le 1

2 C

om

pari

son

of

Case

Excl

usi

on

Rea

son

s fo

r th

e P

re &

Post

In

terv

enti

on

Per

iod

s of

the

Stu

dy -

All

erd

ale

Case

excl

usi

on

rea

son

s

Pre

-in

terv

enti

on

(01/0

3/1

996 t

o 2

9/0

2/2

000)

Post

-in

terv

enti

on

(01/0

8/2

000 t

o 3

1/0

8/2

002)

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

TO

TA

L

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

TO

TA

L

2000

2000

2001

2002

1996

1997

1998

1999

TA

BL

E 1

2 C

OM

PAR

ISO

N O

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FO

R T

HE

PR

E &

PO

STIN

TE

RV

EN

TIO

N P

ER

IOD

S O

FT

HE

ST

UD

Y-

AL

LE

RD

AL

E

Cry

ptos

pori

dios

is I

nter

vent

ion

Stud

y 1

Mar

ch 1

996

to 3

1 A

ugus

t 20

02



82

Cry

pto

spori

dio

sis

Inte

rven

tion

Stu

dy 1

Marc

h 1

996 t

o 3

1 A

ugu

st 2

002

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

(n)

%(n

)%

Sec

on

dary

2(9

.5)

2(1

8.2

)5

(21.7

)8

(20.5

)0

(0.0

)17

(17.9

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Sec

on

dary

& i

nte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Sec

on

dary

& c

on

tact

wit

h c

on

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Con

tact

wit

h a

con

firm

ed c

ase

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Bee

n a

bro

ad

2(9

.5)

0(0

.0)

0(0

.0)

2(5

.1)

0(0

.0)

4(4

.2)

1(2

5.0

)0

(0.0

)1

(50.0

)2

(22.2

)

Vis

itor

to s

tud

y a

rea

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Res

iden

t ou

tsid

e st

ud

y a

rea

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Non

res

pon

der

1(4

.8)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

1(1

.1)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Ref

use

d t

o p

art

icip

ate

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Not

inte

rvie

wed

/Soci

al

reaso

ns

0(0

.0)

0(0

.0)

1(4

.3)

0(0

.0)

0(0

.0)

1(1

.1)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

Inte

rvie

wed

pre

vio

usl

y0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Du

al

infe

ctio

n0

(0.0

)0

(0.0

)1

(4.3

)0

(0.0

)0

(0.0

)1

(1.1

)0

(0.0

)0

(0.0

)0

(0.0

)0

(0.0

)

Du

al

infe

ctio

n a

nd

bee

n a

bro

ad

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

0(0

.0)

No d

iarr

hoea

0(0

.0)

0(0

.0)

0(0

.0)

1(2

.6)

0(0

.0)

1(1

.1)

0(0

.0)

1(3

3.3

)0

(0.0

)1

(11.1

)

Tota

l ex

clu

ded

case

s5

(23.8

)2

(18.2

)7

(30.4

)11

(28.2

)0

(0.0

)25

(26.3

)1

(25.0

)1

(33.3

)1

(50.0

)3

(33.3

)

Tota

l p

rim

ary

case

s16

(76.2

)9

(81.8

)16

(69.6

)28

(71.8

)1

(100.0

)70

(73.7

)3

(75.0

)2

(66.7

)1

(50.0

)6

(66.7

)

Tota

l ca

ses

rep

ort

ed21

(100.0

)11

(100.0

)23

(100.0

)39

(100.0

)1

(100.0

)95

(100.0

)4

(100.0

)3

(100.0

)2

(100.0

)9

(100.0

)

N.B

. F

urt

her

vali

dati

on p

erf

orm

ed J

une 2

002. 3 c

ases "

Aw

ay g

reate

r th

an 7

days" r

e-d

efi

ned. 1 t

ravell

ed a

bro

ad a

nd 2

inclu

ded i

n s

tudy

Table

does n

ot

show

the 1

pri

mary

and 2

exclu

ded c

ases t

hat

occurr

ed i

n t

he f

ilte

r com

mis

sio

nin

g p

eri

od 0

1/0

3/2

000 t

o 3

1/0

7/2

000

Def

init

ion

s

All

exclu

sio

ns are

due t

o t

he s

tate

d e

vent

in t

he 1

4 d

ays p

rior

to t

he o

nset

of

sym

pto

ms o

ther

than f

or

non r

esponders

, re

fusals

and t

hose n

ot

inte

rvie

wed f

or

socia

l re

asons a

nd i

nte

rvie

wed p

revio

usly

Secondary

= C

ase w

here

a m

em

ber

of

their

household

had d

iarr

hoea o

r confi

rmed c

rypto

spori

dio

sis

in t

he 1

4 d

ays p

rior

to t

he c

ase's

ill

ness

Dual

infe

cti

on =

Case w

ith c

onfi

rmed c

rypto

spori

dio

sis

& a

noth

er

path

ogen c

apable

of

causin

g g

astr

o-i

nte

sti

nal

illn

ess

Resid

ence o

uts

ide s

tudy a

rea =

Case l

ives a

dja

cent

to s

tudy a

rea a

nd o

nly

identi

fied a

s o

uts

ide s

tudy a

rea a

t in

terv

iew

2001

2002

TO

TA

L

1996

1997

2000

Tab

le 1

3 C

om

pari

son

of

Case

Excl

usi

on

Rea

son

s fo

r th

e P

re &

Post

In

terv

enti

on

Per

iod

s of

the

Stu

dy -

Cop

elan

d

Case

excl

usi

on

rea

son

s

Pre

-in

terv

enti

on

(01/0

3/1

996 t

o 2

9/0

2/2

000)

Post

-in

terv

enti

on

(01/0

8/2

000 t

o 3

1/0

8/2

002)

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

TO

TA

L

Nu

mb

er o

f C

ase

s (n

) b

y c

ale

nd

ar

yea

r of

stu

dy &

per

cen

tage

(%)

of

tota

l ca

ses

rep

ort

ed

2000

1998

1999

TA

BL

E 1

3 C

OM

PAR

ISO

N O

FC

ASE

EX

CL

USI

ON

RE

ASO

NS

FO

R T

HE

PR

E &

PO

STIN

TE

RV

EN

TIO

N P

ER

IOD

S O

FT

HE

ST

UD

Y-

CO

PE

LA

ND

Cry

ptos

pori

dios

is I

nter

vent

ion

Stud

y 1

Mar

ch 1

996

to 3

1 A

ugus

t 20

02



83

b) Controls: Exclusions andexclusion reasons in the pre andpost intervention periods

Tables 14 and 15 show the comparisonof the controls in the differentcategories: not contacted (B), contactedbut not incorporated (A), incorporatedinto study, for the pre and postintervention periods. Category B, notcontacted, represented controls on thelist generated by the computer that hadnot been contacted by the RA.However, checks were made againstnames held on the database, to ascertainwhether they were cases or controlsalready in the study. Category A,contacted but not incorporated controlswere those that had been contacted, buthad not been incorporated; the manyreasons for controls not to beincorporated into the study wereexamined further.

Comparisons between the pre and postintervention periods show thatproportionally more controls (48% oftotal) in the not contacted (B) grouphad to be generated to achieve therequired three controls per case in thepost intervention period [Table 14].More controls 40% were incorporatedinto the study in the pre interventionperiod compared to the postintervention period (22%). Theproportion of controls that had beencontacted but not incorporated,category A, were approximately thesame in the two time periods.

As the study progressed, in year 2000, itwas found that some of the controls onthe generated list were cases andcontrols already in the database andextra controls had to be generated toavoid duplication. The number of

controls in the list generated by thecomputer increased from five controls,in the pre-intervention period to tencontrols as a routine in the postintervention period. The difficulty inobtaining the required three controlsper case was seen more acutely incertain towns such as Thursby andMillom. Hence in the Year 2000, thenumber of controls seen in Category B,not contacted, was more than inprevious years, and was a mixture ofunused controls and duplicates of casesand controls already in the study.However, by the end of Year 2001, threecontrols were easily achieved for a casein a larger town, leaving many unusedcontrols on the list [Table 14].

Comparisons of the reasons the controlsin Category A, (that had been contactedbut not incorporated) did notparticipate in the study, in the two timeperiods, show that the main reason was‘no answer’, which was that intervieweeswere not present at requested interviewtime and there was no response tofollow up; 40.3% in the preintervention and 28.8% in the postintervention period [Table 15]. A smallproportion of controls in both periodsalso contacted RA to cancelappointments or to report unavailabilityat the requested interview time. The RAcancelled 6.1% of control interviews inthe pre intervention period and 26% inthe post intervention period, afterachieving the three required controls.The proportion of controls’ refusals15.1% in the post intervention periodwas more than the 7.4% in the preintervention period. Amongst controls that had beeninterviewed, diarrhoea remained animportant reason for exclusion in bothtime periods.



84

Cry

pto

spo

rid

iosi

s in

terv

enti

on

stu

dy

1 M

arc

h 1

99

6 t

o 3

1 A

ug

ust

20

02

Ca

ses

Case

s

Pri

mar

y c

ases

tota

l (b

y d

ate

of

repo

rtin

g)

Pri

mar

y c

ases

tota

l (b

y d

ate

of

report

ing)

(n)

(n)

As

% o

f

all

contr

ols

in

yea

r

(n)

As

% o

f al

l

contr

ols

in

yea

r

(n)

As

% o

f

all

contr

ols

in

yea

r

(n)

As

% o

f

all

contr

ols

in y

ear

(n)

(n)

As

% o

f

all

con

tro

ls i

n

yea

r

(n)

As

% o

f al

l

con

tro

ls i

n

yea

r

(n)

As

% o

f

all

con

tro

ls i

n

yea

r

(n)

As

% o

f al

l

con

tro

ls i

n

yea

r

19

96

31

96

41

%4

720%

92

39%

235

100%

- -

- -

- -

- -

-

19

97

20

46

43

%2

422%

37

35%

107

100%

- -

- -

- -

- -

-

19

98

39

12

34

3%

75

26%

89

31%

287

100%

- -

- -

- -

- -

-

19

99

61

20

03

9%

16

432%

154

30%

518

100%

- -

- -

- -

- -

-

20

00

23

33

%0

0%

667%

9100%

616

17%

16

17%

64

67%

96

100%

20

01

- -

- -

- -

- -

-6

18

23%

35

44%

26

33%

79

100%

20

02

- -

- -

- -

- -

-6

19

28%

22

32%

27

40%

68

100%

To

tal

15

34

68

40

%3

10

27%

378

33%

1156

100%

18

53

22%

73

30%

117

48%

243

100%

(*)

Incl

ud

es i

nco

rpo

rate

d c

on

tro

ls i

nte

rvie

wed

up

to a

nd i

ncl

udin

g 3

Sep

tem

ber

2002 t

o m

ainta

in c

ase

asso

ciat

ion.

Def

init

ion

s

Ca

teg

ory

A

= C

on

tro

ls c

on

tact

ed f

rom

lis

t g

ener

ated

, le

tter

s se

nt

/ vis

its

mad

e /

inte

rvie

ws

conduct

ed.

Ca

teg

ory

B =

Co

ntr

ols

in

lis

t g

ener

ated

by

co

mp

ute

r, n

o c

onta

ct m

ade

eith

er b

y p

ost

, te

lephone

or

vis

its.

Chec

ks

mad

e ag

ainst

nam

es h

eld o

n d

atab

ase.

See

nex

t ta

ble

(R

EF

*)

for

excl

usi

on

rea

son

s fo

r ca

tegory

A c

ontr

ols

Ta

ble

14

C

om

pa

riso

n o

f co

ntr

ol

usa

ge

for

def

ined

per

iod

s of

the

stu

dy

Inco

rpo

rate

d

into

stu

dy

(by

dat

e o

f

inte

rvie

w)

Co

nta

cted

but

not

inco

rpora

ted

(Cat

egory

A)

Not

conta

cted

(Cat

egory

B)

Tota

l pro

vid

ed

by N

CH

A

Con

trols

Yea

r

Pre

-in

terv

enti

on

per

iod

1 M

arc

h 1

996 t

o 2

9 F

ebru

ary

2000

Post

-in

terv

enti

on

per

iod

1 A

ugu

st 2

000 t

o 3

1 A

ugu

st 2

002

Du

e to

ro

un

din

g o

f th

e in

div

idu

al %

's i

n e

ach

yea

r, t

he

sum

of

thes

e fo

r th

e yea

r m

ay n

ot

equal

100%

N.B

. T

able

do

es n

ot

sho

w t

he

4 p

rim

ary

cas

es, 1

6 i

nco

rpora

ted c

ontr

ols

, 9 C

ateg

ory

A &

82 C

ateg

ory

B c

ontr

ols

duri

ng t

he

filt

er c

om

mis

sionin

g p

erio

d 0

1/0

3/2

000 t

o 3

1/0

7/2

000

Con

trols

Inco

rpora

ted

into

stu

dy

(by d

ate

of

inte

rvie

w)

(*)

Conta

cted

but

not

inco

rpora

ted

(Cat

egory

A)

Not

conta

cted

(Cat

egory

B)

Tota

l pro

vid

ed

by N

CH

A

Cry

ptos

pori

dios

is I

nter

vent

ion

Stud

y 1

Mar

ch 1

996

to 3

1 A

ugus

t 20

02

TA

BL

E 1

4 C

OM

PAR

ISO

N O

FC

ON

TR

OL

USA

GE

S F

OR

DE

FIN

ED

PE

RIO

DS

OF

TH

E S

TU

DY

(15)

for

excl

usi

on

rea

son

s fo

r ca

teg

ory

A c

ontr

ols



85

n (%) n (%)

1) No Answer 125 40.3% 21 28.8%

2) Not convenient 34 11.0% 3 4.1%

3) Cancelled 19 6.1% 19 26.0%

4) Address not found 3 1.0% 0 0.0%

5) Diarrhoea 47 15.2% 6 8.2%

6) Abroad 8 2.6% 4 5.5%

7) Residence outside area 2 0.6% 0 0.0%

8) Wrong age 9 2.9% 0 0.0%

9) Moved 27 8.7% 7 9.6%

10) Interviewed prior 7 2.3% 1 1.4%

11) Refused 23 7.4% 11 15.1%

12) Unknown 3 1.0% 0 0.0%

13) Not resident 14 days prior 3 1.0% 1 1.4%

Total 310 100.0% 73 100.0%

Exclusion reason

Number of controls

Pre-intervention Post-intervention

Definitions1) No answer = Not present at requested interview time and no response to follow up as per interview protocol.2) Not convenient = Control makes contact to either cancel the requested interview or confirm reasons for

being un-available when RA has visited at the requested time e.g. Control away from home. 3) Cancelled = The interview request was cancelled by the RA for administrative reasons e.g. sufficient controls

obtained or case excluded.4) Address not found = Control address could not be found.5) Diarrhoea = Protocol exclusion reason6) Abroad = Travel abroad in the 14 days prior to interview, a protocol exclusion reason.7) Residence outside area = Control address found to be outside study area, a protocol exclusion reason.8) Wrong age = Age of control is not in the same age band as that of the case, a protocol exclusion reason.9) Moved = Control not resident at the address provided.

10) Interviewed prior = Control or a member of their household previously interviewed as a control or case.11) Refused = Declined to be interviewed or give consent after interview.12) Unknown = Reason for exclusion not recorded on the administrative database.13) Not resident in the study area in the 14 days prior to interview.

TABLE 15 COMPARISON OF CONTROL EXCLUSION REASONS CONTACTED BUT NOTINCORPORATED (CATEGORY A)

N.B. Due to rounding of the individual %, the sum of these may not equal 100%Table does not show the 9 excluded (6 cancelled by RA, 1 refused, 2 no answer) controls in the filter commisioning period 01/03/2000 to 31/07/2000

Administrative errors, such as controlsof wrong age group, residence outsidestudy area or address not found werenot seen in the post intervention period.In June 2002, a revalidation exercisereclassified cases and controls in thecategory of ‘away from the study areamore than 7 days’. Whilst travel abroadwas a criterion for exclusion, travel inthe United Kingdom was included inthis study for analysis. As a result ofthis reclassification, no controls were

featured in this category in theintervention study. The total number ofcontrols incorporated in theintervention study was 468 in the preintervention period and 53 in the postintervention period. In addition, therewere 16 controls that fulfilled the studycriteria, in the commissioning period,featured in the footnote of the table[Table 14]. The total number ofcontrols for the whole period wastherefore 537.


Statistics Report : Intervention Study

86

Impact of installation of Membrane Filtration of drinking water on the incidence and risk factors

for sporadic cryptosporidiosis, Copeland and Allerdale local authorities 1996 to 2002

Report by Neville Q Verlander, Andre Charlett, Mark Reacher (January 2003)

IntroductionA case control study of risk factors of sporadic cryptosporidiosis was undertaken in residents of theLocal Authority areas of Copeland and Allerdale in Cumbria North West England arising between1 March 1996 and 31 August 2002.

The study population was served by a variety of water sources (Table 1). Approximately one thirdof the study population was served by each of the water sources of Ennerdale and Crummock,both sources were supplied unfiltered until March 2000, when installation of Membrane Filtrationcommenced. The remaining third of residents were served by water from a variety of smallersources, some of which had been treated with conventional sand filtration between 1 March 1996and 29 February 2000. These were combined into a third category “other” indicating receipt of avariety of conventionally treated, unfiltered, and private source water.

TABLE 1 WATER SOURCES, ZONES, FILTRATION AND POPULATIONS SERVED, COPELANDAND ALLERDALE LOCAL AUTHORITIES, 1996 TO 2002

Water sources Water zones Filtration status Average population priorto installation of membrane filtration

Crummock Crummock North Unfiltered 1 March 1996 to 58,295Crummock South 29 February 2000 then

installation of Membrane Filtration commenced March 2000

Ennerdale Ennerdale North Unfiltered 1 March 1996 to 47,780Ennerdale South 29 February 2000 then

installation of Membrane Filtration commenced March 2000

�Other� QuarryHill Variety of supplies* throughout 59,699Fellside the study periodHayknott 1 March 1996 to 31 August 2002HausegillUnderscarBridegendMillomMixed Private*

* A variety of conventionally treated and unfiltered water, and private supplies.



87

The results of the case control study on cases arising between 1 March 1996 and 29 February 2000have already been presented (Sporadic Cryptosporidium in West Cumbria: A case control study(February 2002)). This study indicated that consumption of mains tap water was an independentrisk factor for infection and established that a dose response relationship existed between ingestionof mains tap water and risk of cryptosporidiosis.

In order to address this risk, Membrane Filtration was installed by the water undertaker as anadditional step in treating water from the Crummock and Ennerdale sources beginning in March2000 (Table 1).

Prolongation of enrolment to the case control study provided an opportunity to examine theimpact of the installation, commissioning and operation of Membrane Filtration in thepopulations receiving water from the Crummock and Ennerdale sources, compared with the samepopulations prior to the installation of Membrane Filtration and compared to the populationserved by “other” water sources. The “other” water sources comprises of those sources which hadbeen provided with conventionally treated and unfiltered water throughout the study periods, andprivate supplies (That is before, during and after installation of Membrane Filtration of theCrummock and Ennerdale sources). There have been no major changes to the “other” watersources during the course of the study.

The United Kingdom was struck by a severe epidemic of Foot and Mouth Disease (FMD) inLivestock during 2001. The first and last cases were diagnosed in weeks 8 and 39. The epidemicwas contained by a variety of policies, notably mass slaughter of livestock, restriction of publicaccess to the countryside and restriction of animal movements. Voluntary containment of animalsfrom normal pastures was also reported to have been common.

The Foot and Mouth Epidemic was associated with a substantial fall in national reporting of cryp-topsoridiosis, which was most marked in the North West Region, including Cumbria. This areawas historically had the highest rates cryptosporidiosis in man and high sheep and cattle densitiesand was particularly hard hit by the FMD epidemic and its controls. The reasons for the declinein human cryptosporidiosis associated with the FMD epidemic cannot be deduced with certainty,but would be consistent with lower levels of Cryptosporidium associated livestock faecalcontamination of water sources combined with lower public access to the countryside. The FMDepidemic is anticipated to cause a permanent change to the economy and ecology of Cumbria.

The FMD epidemic occurred during the planned period of recruitment to the post intervention(post installation of Membrane Filtration) study. Interpretation of trends within the studypopulation must therefore consider the impact of the FMD epidemic as well as the impact thatmay be explained by installation of Membrane Filtration.



88

Methods Data sources, data manipulation, the selection of variables for inclusion in a multivariable riskfactor analyses and multivariable methods were the same as those used for the pre interventionphase of the study and are described in the pre intervention phase report.

Additionally, Poisson Regression analysis was used to model the impact of the introduction ofmembrane filters and the FMD in livestock on the incidence of human cryptosporidiosis using theconventionally filtered “other” water sources as a reference within the model. Changes in the riskfactors for infection, including consumption of unboiled mains tap water were explored usinglogistic regression.

Division of the study period by Installation of Membrane Filtration and theFoot and Mouth Disease Epidemic

The period of the study was divided into five intervals (Table 2)

1. Pre-installation of membrane filters2. Commissioning of membrane filters3. Established Membrane Filtration prior to the FMD epidemic4. Established Membrane Filtration and the FMD epidemic5. Established Membrane Filtration following the end of FMD epidemic controls

TABLE 2 TIME PERIODS OF OBSERVATION BY INTRODUCTION OF MEMBRANEFILTRATION AND THE FOOT AND MOUTH DISEASE EPIDEMIC IN LIVESTOCK

From To FMD epidemic Crummock Ennerdale Other* interval

1 March 1996 29 February 2000 None No filtration No filtration Conventional filtration

1 March 2000 31 July 2000 None Commissioning Commissioning Conventional membrane filters membrane filters filtration

1 August 2000 20 February 2001 None Membrane filters Membrane filters Conventional established established filtration

21 February 2001 20 January 2002 FMD epidemic Membrane filters Membrane filters Conventional established established filtration

21 January 2002 31 August 2002 Post FMD Membrane filters Membrane filters Conventional epidemic established established filtration

* A variety of conventionally treated and unfiltered water, and private supplies.

Cases of sporadic cryptosporidiosis were related to the water supply zones, water sources andserved populations provided for each time interval by the water undertaker. Counts of cases,seasonality and incidence rates within each time period and for each water supply were examineddescriptively and compared.

TABLE 4 AGE AND SEX DISTRIBUTION AMONG THE WATER SOURCES OF THOSE RECRUITED TO THE STUDY

1/3/96 - 29/2/00 1/3/00 � 31/8/02

Crummock Ennerdale Other Crummock Ennerdale Other

Age Male Female Male Female Male Female Male Female Male Female Male Female

0-5 54 45 72 59 59 71 3 9 4 1 8 11

6-15 40 37 23 23 37 24 7 6 1 2 7 4

16+ 12 21 5 4 15 20 1 0 3 2 11 11

TOTAL 106 103 100 86 111 115 11 15 8 5 26 26



89

Results A total of 175 cases and 537 controls were recruited. Table 3 shows the age, sex and water sourcedistribution, while Table 4 shows the age and sex distribution among the water sources.

TABLE 3 AGE AND WATER SOURCE DISTRIBUTION OF THOSERECRUITED TO THE STUDY

1/3/96 � 29/2/00 1/3/00-31/8/02Cases Controls Cases Controls

AGE0-5 87 273 9 276-15 47 137 7 2016+ 19 58 6 22

WATER SOURCECrummock 56 153 6 20Ennerdale 43 143 3 10Crummock & Ennerdale 99 296 9 30Other 54 172 13 39

SEXMale 83 234 7 38Female 70 234 15 31

TOTAL 153 468 22 69



90

In the period prior to 1 March 2000, twenty three (15%) of the cases were admitted to hospital

due to their illness and their ages ranged from 0 to 14 years with mean and median age of 3.7 and

2 years, respectively. In the period after 29 February 2000, three (14%) of the cases were admitted

to hospital due to their illness and their ages ranged from 3 to 12 years with mean and median age

of 8.3 and 10 years, respectively. Table 6 shows the age and sex distribution of hospitalised cases.

TABLE 6 AGE AND SEX DISTRIBUTION OF HOSPITALISED CASESRECRUITED TO THE STUDY

1/3/96 � 29/2/00 1/3/00-31/8/02

Age Male Female Male Female

0-5 14 5 0 1

6-15 2 2 1 1

16+ 0 0 0 0

Thirty eight cases in the period prior to 1 March 2000 and 4 in the period after 29 February 2000had continuing symptoms at the time of interview and of the remaining, the median duration ofillness was 9 days (range: 2-21) and 10 days (range: 3-20), respectively. The most commonsymptoms experienced by the cases are given in Table 5 below:

TABLE 5 CASE SYMPTOMS OF THOSE RECRUITED TO THE STUDY

1/3/96 � 29/2/00 1/3/00-31/8/02Symptoms n % n %

Diarrhoea 153 100 22 100

Abdominal Pain 110 72 18 82

Vomiting 94 61 10 46

Fever 69 45 9 41

Loss of Appetite 68 50 18 82

Weight Loss 56 44 17 77



91

Figure 1. Annual incidence rate per 100,000 of those

recruited to the study

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

1996 1997 1998 1999 2000 2001 2002

Year

Ra

te

FIGURE 1 ANNUAL INCIDENCE RATE PER 100,000 OF THOSE RECRUITED TO THE STUDY

The annual incidence of sporadic cryptosporidiosis over all water sources combined exceeded 10per 1000,000 in the preintervention phase from 1996 to 2000, peaking in 1999 at over 35 per100,000; and declined to below 10 per 1000,000 in the post intervention and FMD epidemicphase between 2000 and the end of recruitment in August 2002 (Figure 1).



92

A spring peak was apparent in cases prior between 1996 and 2000 but was no longer conspicuousfollowing the introduction of Membrane Filtration (Figures 2 and 3). Figures 2 and 3 are derivedby combining all the water zones.

Figure 2. Average number of primary cases

recruited to the study from 1 March 1996 to 29

February 2000 (Pre-intervention)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

Jan Mar May Jul Sep Nov

Month

Avera

ge n

um

ber

of

cases

Figure 3. Average number of primary cases

recruited to the study from 1 March 2000 to 31

August 2002 (Post-intervention)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

Jan Mar May Jul Sep Nov

Month

Avera

ge n

um

ber

of

cases

FIGURE 2 AVERAGE NUMBER OF PRIMARY CASESRECRUITED TO THE STUDY FROM 1 MARCH 1996

TO 29 FEBRUARY 2000 (PRE-INTERVENTION)

FIGURE 3 AVERAGE NUMBER OF PRIMARY CASESRECRUITED TO THE STUDY FROM 1 MARCH 2000

TO 31 AUGUST 2002 (POST-INTERVENTION)



93

The incidence per 100,000 person years was similar in populations served by Crummock,Ennerdale and Other water sources during the pre intervention phase (Figure 4). A decrease inincidence in Crummock and Ennerdale was seen for the Membrane Filtration commissioningphase (Figure 5) and the established Membrane Filtration phase prior to the FMD outbreak(Figure 6) compared to other water sources, but the 95% confidence intervals overlapped.

Figure 4. Incidence rate per 100,000 person-years of those

recruited to the study and 95% CI 1 March 1996 - 29

February 2000 (Pre-intervention)

0

5

10

15

20

25

30

35

40

Crummock Ennerdale Crummock & Ennerdale Other

Incid

en

ce R

ate


recruited to the study and 95% CI 1 March 2000 - 31 July

2000 (Commissioning membrane filtration)

0

5

10

15

20

25

30

35

40


Incid

en

ce R

ate


recruited to the study and 95% CI 1 August 2000 - 20

February 2001 (Established membrane filtration)

0

5

10

15

20

25

30

35

40


Incid

en

ce R

ate

FIGURE 4 INCIDENCE RATE PER 100,000 PERSON-YEARSOF THOSE RECRUITED TO THE STUDY AND 95% CI

1 MARCH 1996 - 29 FEBRUARY 2000 (PRE-INTERVENTION)


1 MARCH 2000 - 31 JULY 2000 (COMMISSIONING MEMBRANE FILTRATION)


1 AUGUST 2000 - 20 FEBRUARY 2001 (ESTABLISHED MEMBRANE FILTRATION)



94

During and following the FMD epidemic, a decline to incidence rates similar to Crummock andEnnerdale was observed for other water sources, but again with overlapping 95% confidenceintervals (Figures 7 and 8). The confidence intervals are wide because of the small numbers ofcases. The appendix provides the numerical values of the incidence rates and the corresponding95% confidence intervals.


recruited to the study and 95% CI 21 February 2001 - 20

January 2002 (Established membrane filtration and FMD

epidemic)

0

5

10

15

20

25

30

35

40


Incid

en

ce R

ate


recruited to the study and 95% CI 21 January 2002 - 31

August 2002 (Established membrane filtration post FMD

epidemic controls)

0

5

10

15

20

25

30

35

40


Incid

en

ce R

ate


21 FEBRUARY 2001 - 20 JANUARY 2002 (ESTABLISHED MEMBRANE FILTRATION AND FMD EPIDEMIC)


21 JANUARY 2002 - 31 AUGUST 2002 (ESTABLISHED MEMBRANE FILTRATION POST FMD EPIDEMIC CONTROLS)



95

Figure 9 shows the incidence rates dichotomised into before membrane Filtration (1 March 1996to 29 February 2000) and after commissioning and establishment of Membrane Filtration before,during and after the FMD epidemic (1 March 2000 to 31 August 2002).

A considerable reduction in the rates of sporadic cryptosporidiosis was apparent for each of thewater sources reflecting both installation of Membrane Filtration and the impact of the FMDepidemic in livestock. The third of the population receiving other supplies continued to be servedwith water treated by conventional filtration. The decline in this group may therefore be attributedto the FMD epidemic alone . The incidence rates suggest that Crummock and Ennerdaleexperienced a decline in incidence in excess of that which could be explained by the FMDepidemic and which may be attributed to the installation of Membrane Filtration.

Figure 9. Incidence rates of those recruited to the

study per 100,000 person-years before and after

installation of membrane filters

0.0

5.0

10.0

15.0

20.0

25.0

30.0

1 March 1996 - 29 February 2000 1 March 2000 - 31 August 2002

Rate


FIGURE 9 INCIDENCE RATE OF THOSE RECRUITED TO THE STUDYPER 100,000 PERSON-YEARS BEFORE AND AFTER

INSTALLATION OF MEMBRANE FILTERS



96

TABLE 7 MODELLING OF STUDY DATA IN POISSON REGRESSION MODEL

Membrane Filtration Pre Membrane Filtration Phase Post Membrane Filtration Phase

No, Other sources Rate 1 Rate 2

Yes, Crummock and Ennerdale Rate 3 Rate 4

Poisson Regression model of rates

In order to explore the statistical significance of these effects with maximum precision twoassumptions were made: each dichotomising the whole data set.

1. The populations of Crummock and Ennerdale were aggregated into a single group indicatingthe installation of Membrane Filtration, the other source group indicating no installation ofMembrane Filtration.

2. The period of observation was divided into the preintervention (Before installation ofMembrane Filtration) phase 1 March 1996 to 29 February 2000; and post interventionphase (Commissioning and establishment of Membrane Filtration for Crummock andEnnerdale Sources) (1 March 2000 to 31 August 2002)

A Poisson regression model was constructed with the number of sporadic cases ofcryptosporidiosis as the predictor variable and the number of person years of observation as theoffset. The independent effect of Membrane Filtration installation and for the time period beforeand after Membrane Filtration Installation were determined separately. The interaction betweenboth was tested.

In the first model, the impact of the commissioning phase (1 March 2000 to 31 July 2000) andthe post Commissioning phase (1 August 2000 to 31 August 2002) was also modelled. In thesecond model the Commissioning phase was omitted.

Conceptually, the modelling of the data may be described by the 2 by 2 table 7.



97

MODEL 1

Poisson regression Number of obs = 15

LR chi2 (3) = 61.92

Prob > chi2 = 0.0000

Log likelihood = -25.361277 Pseudo R2 = 0.5497

cases | IRR Std. Err. z P>|z| [95% Conf. Interval]

Filter | 1.028594 .1740104 0.17 0.868 .7383182 1.432994

Post inst. | .4140716 .1279217 -2.85 0.004 .226 .7586517

interaction | .3497771 .1628075 -2.26 0.024 .1404722 .8709481

denom |(exposure)

Where IRR are the Incidence Rate RatiosFilter = Rate 3 / Rate 1Post inst. = Rate 2 / Rate 1Interaction denom = Rate 4 / Rate 3

Rate 2 / Rate 1

There is a significant interaction between the two predictors (p=0.024). That is, the decrease inincidence in the water zones with membrane filtration is significantly different from the decreasein incidence in the “other” water zones.

Model 1 included the commissioning phase in the post filtration period and it may be that thetesting of the new filters would have been carried out. If the commissioning period from 1st March2000 to 31st July 2000 is ignored then the following results are obtained.

MODEL 2

Poisson regression Number of obs = 12

LR chi2 (3) = 52.78

Prob > chi2 = 0.0000

Log likelihood = -22.029292 Pseudo R2 = 0.5450

cases | IRR Std. Err. z P>|z| [95% Conf. Interval]

Filter | 1.028594 .1740104 0.17 0.868 .7383182 1.432994

Post inst. | .3867805 .1331551 -2.76 0.006 .1969815 .7594578

interaction | .4022404 .2025709 -1.81 0.071 .1499046 1.079335

denom |(exposure)

The interaction became slightly diminished (p=0.07).



98

The estimated incidence rate ratio in the “other” zones with conventional filtration throughout thestudy period was 0.387 (95% CI 0.197 to 0.759) for the time period after compared to beforeMembrane Filtration installation in Crummock and Ennerdale and may be interpreted as theindependent effect of the FMD epidemic.

For Crummock and Ennerdale sources in which Membrane Filtration was installed, the rate ratiofor sporadic Cryptosporidiosis post compared to pre Membrane Filtration was estimated to be0.156 (95% CI 0.076 to 0.320) Put another way, the introduction of Membrane Filters wereassociated with a reduction in incidence of 85.5% (95% CI: 68.8% to 92.4%), while in “other”water zones with conventional filtration, the reduction over the same time interval was 61.3%(95% CI: 24.1% to 80.3%).

Conclusion

In the post filtration phase of this study there is a very clear reduction in the incidence of sporadiccryptosporidiosis in West Cumbria. The most likely cause of this reduction is the FMD epidemic,however, there is a significantly greater reduction in the incidence in the Crummock andEnnerdale water zones where Membrane Filtration was installed.

This was indicated by an interaction term for the pre- versus postintervention phase; andMembrane Filtration introduced versus conventional filtration reaching standard levels ofsignificance (p= 0.024). That is, the probability that such an interaction could have occurred bychance alone was less than one in twenty.

Despite the confounding effect of the FMD epidemic on the post intervention study, a statisticallysignificant decrease in the incidence of sporadic cryptosporidiosis has been demonstratedfollowing installation of Membrane Filtration.



99

Complementary analysis of incidence of sporadic cryptosporidiosis followingintroduction of Membrane Filtration

The first analysis was based on rates by simplifying the time periods of observation into the periodbefore and after the introduction of Membrane Filtration.

An additional analysis was undertaken in which the five time periods of observation summarisedin table 2 were considered aggregated and then excluding the period of MembraneCommissioning and the FMD epidemic .

Table 8 shows number of months with stated number of cases per month in each period ofobservation.

The p-value for the Kruskal-Wallis test applied to the whole of Table 8 is 0.003, from which it isclear that the number of cases post Membrane Filtration was significantly lower compared to thepre-intervention phase.

The column “filtered and prior to FMD 1 August 2000 to 20 February 2001” represents the onlyperiod of observation in which Membrane Filtration was Established and without theconfounding effect of the FMD epidemic. Comparing this period with the Pre MembraneFiltration interval 1 March 1996 to 29 February 2000, the Kruskal-Wallis test statistic is 0.048 .Thus, even constricting the study interval data to the intervals of observation with EstablishedMembrane filtration and free from the effect of the FMD epidemic, the reduction of incidence insporadic cryptosporidiosis is significant at a level less than the traditional cut off of 0.05 ( A lessthan 1 in 20 probability of observing such a difference by chance). These results are congruentwith the Poisson Regression analysis suggesting a significant reduction in sporadiccryptosporidiosis following installation of Membrane Filtration after removal of an FMDepidemic effect.

TABLE 8 FREQUENCY OF MONTHS WITH STATED NUMBER OF CASES PER MONTHIN EACH PERIOD FOR ALL WATER SOURCES

Number of cases Pre-Membrane Post Membrane Filtrationper month Filtration

Filter Filtered and Filtered FMD Filtered and post1st March 1996 Commissioning prior to FMD 21 Feb 2001 FMD controls

29 Feb 2000 1 March 2000 1 August 2000 20 Jan 2002 21 Jan 200231 July 2000 20 Feb 2001 31 August 2002

0 11 2 4 9 31 9 2 2 1 02 10 1 0 1 33 8 0 0 1 04 1 0 1 0 05 1 0 0 0 06 2 0 0 0 07 0 0 0 0 08 0 0 0 0 09 0 0 0 0 0

>=10 6 0 0 0 0



100

Risk Factor Analysis

Changes in risk factors for sporadic cryptosporidiosis during the five time periods of observation

of the study (Table 2) was undertaken in five steps

Step 1. Exploratory analysis Five sets of contingency tables, one for each time period of observation, were

constructed for each exposure and odds ratios calculated.

Step 2. First selection of variables (main effects)Variables significant at p< 0.2 in any of the five sets of contingency tables were selected

for inclusion in logistic regression models. A sequence of multivariable models were

fitted removing clearly non-significant variables.

Step 3. Selection of significant interaction termsAn interaction term between time period and each of the remaining variables was

included in separate multivariable models. This was done to select a subset of

interactions for simultaneous examination in a multivariable model.

Step 4. Multivariable models investigating interactions The remaining interactions in step 3 were considered together in multivariable models

and non-significant interactions were removed one at a time. This sequence of models

resulted in a model, where all the remaining interactions were significant. However,

the confidence intervals for the odds ratios were very wide, so interactions were

removed one at a time until the interactions were significant and confidence intervals

not too wide. This resulted in the final model.

Step 5. Final model of risk of sporadic cryptosporidiosisThis consisted of a single interaction of daily mains tap water consumption and time

period, adjusted for the other variables (main effects) chosen from step 2.



101

Results

Table 9 shows the odds per pint of drinking water in each of the five study periods, adjusted forthe other variables in the model, as obtained in step 5.

Table 10 on the next page shows the other risk factors tested in the final model without anyinteractions since the interaction between water consumption and time period adjusted for theother variables is not significant (p=0.12).

TABLE 9 ADJUSTED ODDS RATIO (OR) AND 95% CONFIDENCE INTERVAL (CI) PER PINT OF WATER IN EACH PERIOD

Period OR CI

Pre-intervention: 1 March 1996 - 29 February 2000 1.552 1.195, 2.015

Membrane Filter commissioning: 1 March 2000 - 31 July 2000 0.736 0.207, 2.618

Membrane Filtered and prior to foot and mouth disease: 1 August 2000 - 20 February 2001 1.262 0.298, 5.350

Membrane Filtered and FMD: 21 February 2001 - 20 January 2002 19.34 0.609, 608.3

Membrane Filtered post FMD controls: 21 January 2002 - 31 August 2002 6.453 0.916, 46.21



102

TABLE 10 MODEL AVERAGING OVER FIVE PERIODS (*=SIGNIFICANT AT 5% LEVEL)

Adjusted 95% Odds Confidence p valueRatio Interval

Water Zone Private 0.100 0.007, 1.436 0.556Quarry Hill 0.703 0.273, 1.810

Fellside 0.005 0, ∞Hayknott 1.016 0.100, 10.290Hausegill 1.356 0.220, 8.345



Bridgend 0.004 0, ∞Millom 1.502 0.686, 3.288Mixed 0.893 0.320, 2.494

Age 1.002 0.983, 1.021 0.872per year

Water 1.543 1.212, 1.965 <0.001*consumption per pint

Faecal contact Y 2.366 0.970, 5.772 0.063N 1.000


Feed pet left-overs Y 3.746 1.214, 11.56 0.021*N 1.000

Feed pet raw vegetables Y 1.972 0.870, 4.467 0.112N 1.000

Contact with cow farm Y 4.532 1.757, 11.69 0.002*N 1.000

Contact with other farm Y 3.809 1.677, 8.651 0.002*N 1.000

Contact with anyone Y 1.776 0.934, 3.378 0.087with diarrhoea N 1.000Mixed salad Y 0.498 0.266, 0.932 0.024*

N 1.000Sex Male 0.730 0.450, 1.184 0.202

Female 1.000Sewerage system Mains 0.513 0.240, 1.094 0.090

Other 1.000Period Pre-intervention :

1/3/96 - 29/2/00 1.000 0.646Filter commissioning:

1/3/00 - 31/7/00 0.965 0.235, 3.958Filtered and prior to FMD:

1/8/00 - 20/2/01 1.115 0.319, 3.895Filtered and FMD : 21/2/01 - 20/1/02 0.367 0.078, 1.720

Filtered and post FMD controls: 21/1/02 - 31/8/02 0.485 0.138, 1.701


Conclusions

103

Conclusions

Drinking mains tap water was again shown to be significantly associated with sporadiccryptosporidiosis overall.

The numbers of observations in the post intervention period are small and the confidence intervalsin this interval are wide and include unity. It is not possible to conclude that risk of drinking mainstap water has changed in the decreased number of post intervention incident cases.

The risks for other exposures show in table 10 that there was no differential risk by water source,but risk was increased by contact with cow and other farms and feeding pets leftovers.

It should be noted that most of these impacts derive from the higher resolution of thepre- intervention phase. This averaged analysis should be viewed with caution.


Appendix

104

APPENDIX INCIDENCE RATES BY WATER ZONE AND TIME PERIOD FOR PRIMARY CASES RECRUITED TO THE STUDY

Water Zone Time Period Cases Person years Rates per 95% confidence100,000 person Interval

years

Other pre 54 238265 22.66 17.03 to 29.57

Other commissioning 3 24449 12.27 2.53 to 35.86

Other filter pre FMD 4 32257 12.40 3.38 to 31.75

Other filter and FMD 3 51997 5.77 1.19 to 16.86

Other filter post FMD 3 29824 10.06 2.07 to 29.40

Crummock pre 56 233623 23.97 18.11 to 31.13

Crummock commissioning 1 25726 3.89 0.10 to 21.66

Crummock filter pre FMD 1 33970 2.94 0.07 to 16.40

Crummock filter and FMD 1 54902 1.82 0.05 to 10.15

Crummock filter post FMD 3 31490 9.53 1.96 to 27.84

Ennerdale pre 43 191053 22.51 16.29 to 30.32

Ennerdale commissioning 0 20258 0 0 to 18.21

Ennerdale filter pre FMD 1 27223 3.67 0.09 to 20.47

Ennerdale filter and FMD 2 46387 4.31 0.52 to 15.574

Ennerdale filter post FMD 0 26606 0 0 to 13.86

Crummock &Ennerdale pre 99 424676 23.31 18.95 to 28.38

Crummock &Ennerdale commissioning 1 45984 2.17 0.06 to 12.11

Crummock &Ennerdale filter pre FMD 2 61193 3.27 0.40 to 11.81

Crummock &Ennerdale filter and FMD 3 101289 2.96 0.61 to 8.66

Crummock &Ennerdale filter post FMD 3 58096 5.16 1.06 to 15.09


Monitoring Media Coverage

105

Di) Monitoring of Media Coverage(Information Bias)

During the six and a half years studyperiod, there would have been manyopportunities for the study population tobe influenced by many sources.Providing accurate, consistentinformation to the public about thestudy was important. Two press releaseswere issued during the course of thestudy. Doctors were provided withinformation about the study, whichincluded the leaflet given to interviewees,to ensure consistency of informationcirculated to the public.

Adverse publicity in the media couldresult in biased responses; the main effectcould be from local or nationaloutbreaks, identifying particular riskfactors of cryptosporidiosis. During thestudy period, there were several minorreports in local newspapers, whenparents released information aboutinvestigations of their children. A localreporter also misinterpreted a reportsubmitted to Allerdale Local Authorityin regards to the extension of theresearch, and reported that 43 cases over18 months constituted an outbreak. Thelead consultant spoke on radio and tolocal reporters to explain the research.Importantly, no single risk factor washighlighted in all the local media reports.On one occasion, parts of the leaflet usedin the research were printed.

There had not been any local outbreaksduring the study period. However inApril and May 1999, increased publicityarose locally when a cluster of cases wasinvestigated in Allerdale. At the sametime, there was national reporting of anoutbreak in North West Region. Inview of this, a survey was conducted to

examine whether the study populationcould have been influenced by theincreased publicity. For a period of sevenmonths, from April to November 1999,three additional questions on knowledgeand transmission of cryptosporidiosiswere added to the interviews of cases andcontrols. The results showed that themajority (69%) had not heard aboutcryptosporidiosis, and those that hadheard, did not identify a single particularrisk factor [Tables 1,2. Media Intereststudy]. The survey also found that thoseinterviewed two and half months afterthe start of the publicity did not recallinformation from the media. Weconcluded that the study population hadnot been influenced by the increasedpublicity. This survey is shown as ‘MediaInterest Study’ in this section.



107

Media Interest Study (28 April 1999 to 30 November 1999)

BACKROUND: An increase in television and newspaper articles regarding cryptosporidiosis occurred in Cumbria in April and May 1999.

AIM: To ascertain whether this increase in media activity had any influence on the answers given by the interviewees at or up to seven months after the increase in media activity had occurred.

METHOD: Interviewees were asked three extra questions in addition to the case-control study questions to try to ascertain whether the increase in media activity had any influence on their answers.

Extra questions interviewees were asked between the 28 April - 30 November 1999:

1: Had you heard about cryptosporidiosis before you were contacted to participate in thecryptosporidiosis case-control study?

If yes, then continue with extra questions.

2: Can you remember where you heard about cryptosporidiosis?

3: Can you remember what you knew about cryptosporidiosis?

RESULTS:Figure 1 and Table 1 show the interviewees answers to questions 1 and 3 combined.From figure 1 it can be seen that 149 of the 215 interviewees (69%) had not heard ofcryptosporidiosis prior to being contacted to participate in the cryptosporidiosis case-controlstudy, and that of the 66 out the 215 interviewees (31%) who had heard of cryptosporidiosisprior to being contacted, no one single opinion of the illness i.e. it’s symptoms or transmissionmethods stood out from the rest.

Figure 2 and Table 2 show the interviewees answers to question 2From figure 2 it can be seen that of the 20% of interviewees who had heard of cryptosporidiosisprior to being contacted and remembered hearing about cryptosporidiosis from media coverage,all were interviewed before the 10th July. However, it must also be noted that media coverageappears to account for only a small source of cryptosporidiosis information and that inconjunction with question 3, the information was probably not biased as no one single opinionof the illness predominated.

CONCLUSIONS:● The majority of interviewees had not heard of cryptosporidiosis

● In general, from the responses given, the study population had not apparently beeninfluenced by the increased media activity occurring in April and May 1999 in Cumbria.



108

Cases interviewed <10 July = Not

heard of Cryptosporidiosis

(28) 13%

Cases interviewed >10 July = Not


(8) 4%

Controls interviewed <10 July = Not


(87) 40%

Controls interviewed >10 July = Not


(26) 12%

Thought water only (6) 3%

Thought farms only (6) 3%

Knew main symptoms (4) 2%

Knew main methods (4) 2%

Knew main methods & symptoms

(4) 2%

Knew name only (7) 3%

Confused/Vague about

Cryptosporidiosis (12) 6%

Knew of illness through work (9)

4%

Interviewed previously (5) 2%

Not stated (9) 4%

0

5

10

15

20

25

Television only Newspaper only Friend/ Rel. only Combination Other Unknown

Source of Cryptosporidiosis information

Nu

mb

er

of

inte

rvie

wees

Controls interviewed>10th July.

Controls interviewed<10th July.

Cases interviewed>10th July.

Cases interviewed<10th July.

FIGURE 1 INTERVIEWEES KNOWLEDGE OF CRYPTOSPORIDIOSIS PRIOR TO PARTICIPATINGIN THE CRYPTOSPORIDIOSIS CASE-CONTROL STUDY (N=215 INTERVIEWEES)

FIGURE 2 SOURCE OF CRYPTOSPORIDIOSIS INFORMATION OF INTERVIEWEES WHO HADHEARD OF CRYPTOSPORIDIOSIS PRIOR TO PARTICIPATING IN THE

CASE-CONTROL STUDY (N=66 INTERVIEWEES)



109

The interviewee answers given to questions 1 and 2 were split into two time periods:

Time period 1 (T1) = 28/04/99 - 09/07/99 an increase in media activity occurred in this time period.

Time period 2 (T2) = 10/07/99 - 30/11/99 no increase in media activity occurred in this time period.

TABLE 1: QUESTION 1 - HAD YOU HEARD ABOUT CRYPTOSPORIDIOSIS BEFORE BEING CONTACTED?

Heard of? T1 Cases (%) T2 Cases (%) T1 Controls (%) T2 Controls (%) Total (%)

Yes, heard of 9 (24) 3 (27) 44 (34) 10 (28) 66 (31)

No, not heard of 28 (76) 8 (73) 87 (66) 26 (72) 149 (69)

Total 37 (100) 11 (100) 131 (100) 36 (100) 215 (100)

TABLE 2: QUESTION 2 - CAN YOU REMEMBER WHERE YOU HEARD ABOUT CRYPTOSPORIDIOSIS?

Where from? T1 Cases T2 Cases T1 Controls T2 Controls Total (%)

Television only 2 0 6 0 8 (12)

Newspaper only 0 0 5 0 5 (8)

Friend/ Rel. only 2 1 10 1 14 (21)

Combination 1 0 2 1 4 (6)

Other 2 1 8 3 14 (21)

Unknown 2 1 13 5 21 (32)

Total 9 3 44 10 66 (100)


Monitoring Interview Times

110

D ii) Monitoring of time intervalsbetween date of reporting ofcase and interviews of casesand controls (Recall bias)

From the start of the study, both theRAs and the deputising EHOs weremade aware of the importance of earlyinterviews of cases and theircorresponding controls. Arrangementswere made for home interviews to beconducted at times convenient forworking parents and school children,such as after school and workinghours, weekends and evenings. Theresearch assistants monitored the timeintervals between the date of reportingof the case and the date of interviewsof the case and their correspondingcontrols, as a routine.

The standard was to interview cases, assoon as possible on receipt of thereport and to complete the interviewsof the corresponding three controls asnear to the date of the case interviewsas possible, and within two weeks ofthe case interview. An arbitrarymaximum time of four weeks forinterview completion was used as aguide.

Sporadic cryptosporidiosis case-control study 1 March 1996 to 29 February 2000

Tables: 16 - 19

For the period of the sporadic case-control study 1 March 1996 to 29February 2000, 152 were primarycases included in the study. Onehundred and twenty eight (84.2%)were interviewed within one week ofthe case report; 23 (15.1%) wereinterviewed within two weeks, and

one interviewed within four weeks[Table 16].

One hundred and thirty one cases(86.2%) had three or more controls;14 (9.2%) had two controls, and 7cases had one or no controls [Table17]. Examination of the time intervalbetween report of case and completionof interviews of the 131 cases togetherwith their three or more controlsshowed 85 (64.9%) cases and theircontrols were interviewed within twoweeks, and 125 (95.4%) wereinterviewed within three weeks. Foronly 6 (4.7%) cases and their controlswere interviews longer than threeweeks and for one case and its controlswithin eight weeks [Tables 18,19].

Cryptosporidiosis InterventionStudy 1 March 1996 to 31 August 2002

Tables: 20 - 23

The cryptosporidiosis interventionstudy identified 1 March 1996 to 29February 2000 as the pre interventionperiod and 1 August 2000 to 31August 2002 as the post interventionperiod. Cases in the filter-commissioning period were notconsidered.The pre interventionperiod incorporated 153 primarycases. This figure differed from thesporadic case-control study; one extracase was added as a result of theoutcome of further validationconducted in June 2002. The postintervention period incorporated only18 primary cases. Comparison of thetime for completion of interviews ofcases over the two time periodsshowed similar times taken for



111

completion of the interviews, with themajority conducted within 1 week:84.3% in the pre intervention periodand 88.9% in the post interventionperiod [Table 20].

Comparison of the number of controlsper case in the pre and postintervention periods show themajority had three or more controls inboth periods: 131 (85.6%) in the preintervention period and 13 (72.3%) inthe post intervention period. Twenty-two cases (14.5%) in the preintervention period and 5 cases(27.9%) in the post interventionperiod had fewer than two controls[Table 21].

Examination of the time taken tocomplete the interviews of cases andtheir corresponding three or morecontrols, i.e. 131 cases and theircontrols in the pre-intervention periodand 13 cases and their controls in thepost intervention period, showed thatthe majority in both periods wereinterviewed within two weeks; 85(64.9%) in the pre-intervention and 9(69.3%) in the post interventionperiod. A large proportion, 125 casesand their controls (95.6%) in the preintervention period was interviewedwithin three weeks; in the postintervention period, all 13 cases andtheir controls (100%) wereinterviewed within three weeks [Tables22, 23].

Certain difficulties were identifiedduring the course of the study. Someof these were common throughout thewhole period of the research, andincluded refusals, person unavailableat time of visit, person not contactableat the address given. Delays had been

caused by postal delays, cancellation orrescheduling of interviews, long traveltime and parents unavailability at thetime. Some controls that wereinterviewed had to be excludedbecause they did not fulfil the studycriteria, for example controls thatreported diarrhoea. (See exclusionsection in Results).

Controls were not duplicated in thestudy. In year 2000, the fourth year, itwas noted that some controlsgenerated by the computer were casesor controls already incorporated in thestudy. This was particularly pertinentin certain areas such as Millom orThursby and extra controls had to begenerated. However by the end ofYear 2001, the required three controlsin a larger town was easily achieved,without exhausting the first list of tencontrols.

The Foot and Mouth Outbreak (21February 2001 to 20 January 2002)had a marked effect in the research.Large areas of the countryside wereclosed; many farms were affected inboth local authorities areas and manyanimals were killed.

Face to face interviews were notpossible in many cases and alternativetelephone interviews were offered,which resulted in delays andfrequently non-response. (See sectionIII: 3 Foot and Mouth Chronology).



112

1

2

3

4

Total

Time interval for

interview (weeks)n (%)

128 84.2%

23 15.1%

152 100.0%

Cases

0

1

0.0%

0.7%

Within 1 week

" 2 "

" 3 "

" 4 "

" 5 "

" 6 "

" 7 "

" 8 "

Total

0.8%

(%)n

Time for completion

of interviews (1)

Cases

30.5%

17

40

131 100.0%

4

0.8%1

3.1%

1

13.0%

51.9%68

0 0.0%

0 0.0%

Controls

Number per case (1)

0

1

2

3

4

5

6

Total

121 79.6%

0 0.0%

0 0.0%

Cases

3.3%

9.2%

2 1.3%

152 100.0%

10 6.6%

5

p

14

n (%)

TABLE 17 NUMBER OF PRIMARY CASES, N (%) WITH REFERENCE TO NUMBER OFCONTROLS PER CASE.

1)Table does not show 32 controls retained for analysis but not associated with a case following exclusion of the case. Table includes one case with two controls in the set which were completed after 29 February 2000

Sporadic Cryptosporidiosis Case - Control Study1 March 1996 to 29 February 2000

TABLE 18 TIME INTERVAL BETWEEN REPORT OF CASE & COMPLETION OF INTERVIEWSFOR CASE AND CORRESPONDING SETS OF 3 OR MORE CONTROLS. (131 CASES)

N.B. Due to rounding of individual %, these may not total to 100%

1) Period starts on date of reporting of primary case to the Health Authority & concludes with the date of completion of the control interviews. The resultant number of days are then categorised into a relevant weekly band that includes this period.

TABLE 16 TIME INTERVAL BETWEEN REPORTING DATE AND COMPLETION OF PRIMARYCASE INTERVIEW, N (%) IN WEEKS.



113

Total

i) 2.4

ii) 1-4

iii) 2.5, 3

8

1

2

3

5

1

17

62 i) 2.3

ii) 1-8

iii) 2, 2

4 10

i) 2.5

ii) 2-4

iii) 2.5, 2

7%

6 2

1 4

3 3

1

3

2 14 9%

1

6

4

3

2

3

4

1

37

3121 81%

1

n (%) iii) Median & Mode

Number of

controls in

each set (1)

Total cases for control set

(2) Number of cases

Time taken to

complete set in

weeks (3)

Time taken (Weeks)

i) Mean

ii) Range

i) 2.4

ii) 1-5

4

1 5

1

23

iii) 2, 2

5 3%

1

150 100% 150

TABLE 19 ANALYSIS OF COMPLETION OF INTERVIEW TIMES FOR PRIMARY CASES &SETS OF CONTROLS 1 MARCH 1996 TO 29 FEBRUARY 2000.

N.B.1) Table does not show 32 controls retained for analysis but not associated with a case following exclusion of the

case. Also includes one case with two controls in the set that were completed after 29 February 20002) Table does not show 2 cases where the associated controls for the set were not recorded in the administrative

database3) Period starts on date of reporting of primary case to the Health Authority & concludes with the date of

completion of the control interviews. The resultant number of days are then categorised into a relevant weekly band that includes this period.

Sporadic Cryptosporidiosis Case - Control Study



114

Within 1 week

" 2 "

" 3 "

" 4 "

" 5 "

" 6 "

" 7 "

" 8 "

Total 131 100.0%

0 0.0%1 0.8%

13 100.0%

Time for

completion of

interviews (1)

Pre-intervention (2) Post-intervention

(01/03/1996 to 29/02/2000) (01/08/2000 to 31/08/2002)

n (%) n (%)

12.2% 4 30.8%

69 52.7% 5 38.5%

16

40 30.5% 4 30.8%

4 3.1% 0 0.0%

0.0%

1 0.8% 0 0.0%

0 0.0% 0 0.0%

0 0.0% 0

Controls

0

1

2

3

4

5

6

Total

Pre-intervention (2) Post-intervention

(01/03/1996 to 29/02/2000) (01/08/2000 to 31/08/2002)

3

1 5.6%0 0.0%

1 0.7%

1 5.6%

1 5.6%

50.0%

16.7%

120 78.4% 9

5 3.3%

14 9.2% 3

2.0% 1 5.6%

n (%)

Number per case

(1)n (%)

Cases

10 6.5% 2 11.1%

153 100.0% 18 100.0%

TABLE 20 TIME INTERVAL BETWEEN REPORTING DATE AND INTERVIEW OF PRIMARYCASES, N (%), FOR DEFINED PERIODS OF THE STUDY.

TABLE 22 COMPARISON OF TIME INTERVAL BETWEEN REPORT OF CASE & COMPLETIONOF INTERVIEWS FOR CASE AND CORRESPONDING SETS OF 3 OR MORE CONTROLS, FOR

DEFINED PERIODS OF THE STUDY. (131 CASES PRE-INTERVENTION & 13 CASESPOST-INTERVENTION)

N.B. Table does not include 4 primary cases (1 interviewed within 1week and 3 within 2 weeks) in the filtercommissioning period 01/03/2000 to 31/07/20001) Period starts on date of reporting of primary case to the Health Authority & concludes with the date of


2) Includes a case where the two control interviews were completed after 29/02/2000

Cryptosporidiosis Intervention Study 1 March 1996 to 31 August 2002

1

2

3

4

Total

16

2

18

88.9%

11.1%

100.0%

0

23 15.0%

129 84.3%

n (%)

Time interval

between reporting

& interview

(weeks)

Pre-intervention Post-intervention

(01/03/1996 to 29/02/2000) (01/08/2000 to 31/08/2002)

n (%)

0

153 100.0%

0.0%

0.0%

0

1

0.0%

0.7%

N.B. Table does not include 4 primary cases interviewed within 1 week in the filter commissioning period01/03/2000 to 31/07/2000

TABLE 21 COMPARISON OF NUMBER OF PRIMARY CASES, N (%) BY NUMBER OFASSOCIATED CONTROLS IN SET, FOR DEFINED PERIODS OF THE STUDY.

N.B. Table does not include 4 primary cases (2 with 3 controls and 2 with 4 controls) in the filtercommissioning period 01/03/2000 to 31/07/20001) Table does not show 32 controls retained for analysis but not associated with a case following exclusion of

the case. 2) Includes one primary case with two controls in the set which were completed after 29 February 2000



115

6

Total

5 2 1.17%1 3 ii) 1-3, iii) 2, No mode

-

i) 2.2

iii) 2, 2

i) 2.3

ii) 1-8

iii) 2, 2

1

i) 2.2

ii) 1-4

iii) 2, 3

ii) 1-4

i) 2.4

i) 2

Time taken (Weeks)

ii) Range

1

3

3

n (%)

Time taken to

complete set in

weeks (3)

i) Mean

131

4 144

3 76.61%3

1

1

19

69 2

38 3

2 17 9.94%

5

4

7

1

1 4

4

2

3

5

8

171 100.00% 171

3 2 ii) 1-5

iii) 2, 2

1 6 3.51%

1

5

2

1

Number of cases Total cases for control set (2)

Number of

controls in

each set (1)

1 1

8 2

1

1

8.19%

iii) Median & Mode

0.58%

4

1

1

TABLE 23 ANALYSIS OF COMPLETION OF INTERVIEW TIMES FOR PRIMARY CASES &SETS OF CONTROLS 1 MARCH 1996 TO 31 AUGUST 2002

N.B.1) Table does not show 32 controls retained for analysis but not associated with a case following exclusion of

the case.2) Table includes 4 primary cases in the Filter commissioning period 1 March 2000 to 31 July 2000 and does

not show 4 cases without an associated set of controls recorded in the administrative database3) Period starts on date of reporting of primary case to the Health Authority & concludes with the date of


Cryptosporidiosis Intervention Study


Discussion : Case control study

117

Case Control Study

This is the first prospective case-control studyinto sporadic cryptosporidiosis in the UnitedKingdom (UK). In the past, studies onsporadic cases in the UK had focused onclinical and epidemiological features of casesin different settings rather than prospectivecase-control studies [5, 6, 9, 55].

Association with drinking waterThe study found a strong statisticallysignificant association between illness due toCryptosporidium and drinking unboiled tapwater in all the water supply zones in Allerdaleand Copeland. The strong association wasconsistently found in all the single andmultivariate analyses. The test for linear trendfor consumption of water showed that odds ofillness increased by approximately 40% witheach extra pint of unboiled water consumed aday. These results were unlikely to haveoccurred by chance.

Water had been recognised as one of theroutes of transmission in outbreakinvestigations. Many outbreaks in the USAand UK had shown strong associationbetween cryptosporidiosis and consumptionof mains water from different types of watersources: filtered, unfiltered surface water,ground water, and even private water [12, 23-33]. The UK Expert Group onCryptosporidium in water supplies identifiedseveral factors that could contribute to thetotal risk of infection, which included rawwater quality, barriers in the water treatmentprocesses of the water supply and thesusceptibility of the consumer. The raw waterquality would also depend on backgroundenvironmental factors, [12, 17, 48].

The Study AreaThe local authorities of Allerdale andCopeland are rural areas with many arablefarms. Within the two local authorities liesthe protected land of the Lake DistrictNational Park, an area of natural beauty withlakes, mountains and forests, attracting manytourists each year.

There are a considerable number of farmanimals and a diversity of wild life in thestudy area. The 1997 census from theMinistry of Agriculture, Food and Fisheries,now superseded by the Department ofEnvironment, Food and Rural Affairs (Defra),reported 1400 dairy and animal farms with180,000 cattle and calves and 700556 sheepin Allerdale and Copeland. [see section III:3].Cryptosporidium can be found in wild as wellas domestic animals [15, 16]. The report ofthe UK Expert Group in 1995 quotedresearch, which demonstrated that calves andadult cattle could excrete large amounts ofCryptosporidium oocysts intermittently andover long periods [48, 56]. The localVeterinary Laboratories Agency of Defrareported over 50 isolates of Cryptosporidiumin individual herds of cattle and sheep in thestudy area each year [see section III: 3].Laboratory submissions were mainly fromcalves and lambs with diarrhoea andrepresented only a small proportion of theanimal cryptosporidiosis present in the animalpopulation of the area.

Sheep, lamb and cattle graze freely in openfields. Sheep also roam freely in largeunfenced ‘fells’ (mountain side grassland) andfields criss-crossed by roads displayingwarning signs to motorists to avoid sheep.These open fields and fells are often alsoadjacent to or are intersected by streams and

Discussion



118

rivers which feed into lakes that are thesurface reservoirs from which public watersupplies are derived. The spraying of fieldswith slurry is common practice. Research,outlined in the reports of the UK ExpertGroup, showed Cryptosporidium oocysts to bewidespread, in all areas of farm waste and inall types of environmental water, in lownumbers [12, 17, 48]. Oocysts are able tosurvive dormant but viable for months inclear water or moist cool soil [12, 17, 48].The 1995 Expert Group’s report pointed tosurveys conducted by the National ResearchProgramme, which examined the prevalenceof oocysts in different source waters [48,57].These showed positive samples (0.9 to 57%)in various lowland rivers sites, with oocystsconcentrations ranging from 0.06 to 2.7 perlitre. An upland waters survey found that11% contained low concentrations of oocysts,ranging from 0.0019 to 0.12 per litre, with amaximum concentration of 2.7 oocysts perlitre found in another survey. In the studyarea, large parts of the land surrounding thenatural lakes are protected land of theNational Park. Private farms, with grazinganimals, front several shores of these lakes.Some of the lakes are also accessible to thepublic for recreational activities, such asfishing, boating or swimming.The local background factors and collatedresearch (identified in the reports of the UKExpert Group) suggest that there is a highprobability that low concentrations ofCryptosporidium oocysts are present in surfacewaters in this study area. Their presence maybe due to various factors such as excess run-offfrom farms, slurry covered fields, or evendirectly from farm and wild animals grazingnear rivers and streams. The concentrationsof oocysts may increase in periods of heavyrainfall. Thus it is highly probable that someof the raw water fed to the treatment works inthe study area contains varyingconcentrations of Cryptosporidium oocysts,on occasion.

Water Supply Zones and Treatment WorksThe study found the same strong associationwith drinking unboiled tap water in all thewater supply zones, irrespective of whetherthe water supply zones received water that wasunfiltered, a variety of conventionally treatedand unfiltered, or private. Two of the waterzones, Ennerdale and Crummock, at the timeof this study, were served by unfiltered butdisinfected water. Unfiltered water isconsidered to be at higher risk fromCryptosporidium than filtered water fromconventional treatment works. The UKExpert Group examined treatment works aspart of their evaluation of the risks ofCryptosporidium in water. They concludedthat disinfection currently in place in watertreatment works is not effective againstCryptosporidium [48, 58, 59, 60]. Physicalremoval of the oocysts would be required,ideally with appropriate filters, matched tothe size of the oocysts. The Expert Groupstressed the need to apply the multiple barrierapproach in water treatment and drewparticular attention for the need to optimisetreatment for removal of Cryptosporidium.The Expert group noted that outbreaks ofcryptosporidiosis in public water supplieswere usually associated with inadequateprovision or operation of water treatment andthat risk situations were often associated withturbidity breakthrough. Well-operatedtreatment processors are capable of 2-3 logremoval of Cryptosporidium. The results ofCryptosporidium monitoring carried outunder the Water Supply (Water Quality)Regulations 2000 has confirmed that typicaloocyst concentrations in treated water areconsiderably less than 1 oocyst in 10 litres andthat such concentrations are not expected tocause outbreaks of cryptosporidiosis.



119

Researchers have also shown that periodically,low concentrations of Cryptosporidiumoocysts can occur in treated water fromconventional treatment works; however, thelevels will be low, usually less than 1 oocystper litre and can be as low as 0.0004 per litre[61-66]. One report recorded a maximumconcentration of 2.7 oocysts per litre in atreatment works outlet [63].

It is probable that low concentrations ofCryptosporidium oocysts could also be presentin all the potable water in this study area, onoccasion. This could be an explanation for thefinding that the risk of Cryptosporidiuminfection is virtually the same in all thedifferent water supply zones in this study.

Infective DoseLow concentrations of Cryptosporidiumoocysts can cause infections. The infectivedose in humans is low; human volunteerstudies have shown a median infective dose of132 oocysts and that a small dose of 30oocysts could still cause infection in 20% ofthe volunteers [67]. Recent studies on strainsof Cryptosporidium parvum genotype 2; theIOWA, UCP and TAMU strains, showed thatthe infective dose differed among the threeisolates. The TAMU strain was significantlymore infective than the others, with a medianinfective dose of only 9 oocysts [68].

Infection would depend on the immunity ofthe consumer. Human volunteer studies haveshown that immunity is not life long;re-infection after one year in volunteers whohave been previously infected has beenrecorded [69]. Infection can thus be due tovarying parasite virulence and/or immunestatus of the host.

Historical background and monitoring ofwater supply zones in study areaIn 1992, an outbreak of cryptosporidiosisoccurred in the Ennerdale and Crummockwater supply zones. Epidemiologicalinvestigations showed an association betweencases of cryptosporidiosis and drinking mainswater from Ennerdale but not fromCrummock [52]. Since then,Cryptosporidium ‘spot’ sampling had beenconducted several times per week for the rawwaters of Ennerdale and Cornhow treatmentworks. The results showed periodic lowconcentrations of Cryptosporidium oocysts ofless than 1 oocyst per litre. However, theviability and species of these oocysts were notknown [see section III:2]. RoutineCryptosporidium monitoring had not beenconducted at the other conventionaltreatment works at the time of the study.There had not been Cryptosporidiumoutbreaks in the water supply zones served byconventionally treated treatment works in thestudy area. No information was available onprivate water supplies in the study area.

Cryptosporidium genotype resultsThe Cryptosporidium Reference Unit carriedout genotype analysis on faecal isolates of thecases in the study [70-73]. The resultsshowed Cryptosporidium parvum genotype 2to be the dominant group, which suggestsanimal or human origins. Genotype 1 hashuman origins [see section II]. Althoughgenotype 2 can be transmitted from humans,its predominance in the human cases in thestudy area over genotype 1 suggests zoonotictransmission.

Association with farm animalsIt is plausible that there was a significant riskof sporadic cryptosporidiosis arising fromfarms and farm animals. The single variableanalysis showed short farm visits, contact withfarms, farm animals, animal faeces, any othercontact with farm animals, stroking animals



120

to be significant. The risk was increased withthe frequency of farm visits. Themultivariable analysis model that included alldata, showed both short visit at a farm anddrinking unboiled water to be significant(p=0.04, p=0.001, respectively). Frequency offarm contact was also significant in themultivariable analysis that excluded subjectswith mixed water supply (p for trend = 0.02).Outbreaks of cryptosporidiosis haddocumented associations with farm and farmanimals [18-21].

During the study period, a collaborative studytook place together with the local VeterinaryLaboratories Agency (Defra), to examinewhether the human cases in the study hadlinks to laboratory confirmed animalcryptosporidiosis. The results showed thattwo human cases had links to farms thatrecorded animal cryptosporidiosis [see sectionIII: 3]. This positive result, albeit small, addsto the association between human cases andfarm animals identified in the epidemiologicalcase control study.

Association with pet animalsThe result that feeding pet animals with rawvegetables and biscuits was significantlyassociated with cryptosporidiosis, as seen inthe single variable analysis that excludedmixed water supply, may have occurred bychance. Feeding pets raw vegetables wasfound to be borderline significant in themultivariable analysis, using all data. Someresearchers have suggested that pet animalsmay pose a small risk [74] although pets aregenerally not considered to be an importantsource of human infection. The small risk, ifit exists, could be related to possibleenvironmental contamination of shared rawvegetables and biscuits, rather than directcontact with pet animals. The study also didnot show a statistically significant association between cases and direct contact withdomestic pets or pets with diarrhoea.

Hand washingIndividuals who ate food within 1-2 hours ofcontact with farm animals were found to havean increased risk of infection in the singlevariable analysis. Multivariable analysisshowed that after visiting a farm, handwashing before eating, was a significantprotective factor (p=0.002) in the analysisthat excluded individuals with a mixed watersupply. Although this result has to be treatedwith caution, as some individuals with noanimal contact were included, washing handshas long been accepted as a simple andeffective public health measure in theprevention of primary and secondaryinfections relating to many organismsincluding cryptosporidiosis.

Pasteurised milkPasteurised milk was found to be protective inthe multivariable analysis that excludedindividuals with mixed water supply. Thereason for this is unclear, but it could be thatthose who drink milk perhaps may drinkproportionally less water.

Other variablesAll the other variables examined were notfound to be risk factors for sporadiccryptosporidiosis. These include salads, dairyproducts, raw sausages, raw meats, pasteurisedand unpasteurised milk, ice, bottled water,soft drinks, contact or walk past or close toslurry, swimming, water sports or paddling,contact with playgroup, contact with anyonewith diarrhoea (outside the household) travelin the UK outside the study area or differenttypes of sewerage systems. Variables that wereknown to have potential association withcryptosporidiosis had been included in thestudy. It is possible but unlikely that therecould be other risk factors not identified inthe study.



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A recent case-control study in Australia foundpublic toddlers pool to be a common riskfactor in sporadic cryptosporidiosis in twocities [75].

BiasesCase-control studies are prone to biasesespecially when the study period is extended,as in this study (six and a half years).

1) Information Bias relating to media reportsof cryptosporidiosis locally and nationallywas of particular concern. Monitoring ofmedia reports was carried out during theperiod of the study (see Results MediaInterest Study). A survey was conducted in1999, during the period of maximumpublicity, which showed that the studypopulation had not been influenced by themedia reports. Importantly, the effects of thelocal publicity appeared to be short-lived andconfined to the period of heightened mediaactivity. Therefore it would also be unlikelythat the study population could have beeninfluenced by earlier media coverage, whichwould include the cryptosporidiosis outbreakin West Cumbria in 1992.

2) Recall bias could occur if there was a longdelay between the time of illness in a caseand the time of interview. Comparisonsbetween cases and controls may not be validif a long time gap exists between interviewsof cases and the controls. Efforts were madeto conduct early interviews of both cases andcontrols during the whole period of thestudy. Monitoring of the times of interviewsshowed that 84% of the cases wereinterviewed within one week of reportingdate and all were interviewed within fourweeks. The average time between the date ofreporting the case and completion ofinterviews of the case and correspondingcontrols was two weeks for the 85% of caseswith three or more controls. Recall biaswould therefore be minimal.

3) Interview/Response/selection biases werealso considered in the study. Interviews wereconducted by three research assistants (RA)supported by two environmental healthofficers (EHO’s). They were all trained bythe same lead consultant and followed thesame protocol for contacting cases andcontrols and the guidance on interviews setout in the Expert Group 1998 report. Apictorial leaflet showing different drinkingutensils was shown to interviewees to assessliquid consumption.

Response bias may be possible in cases thathad increased their water consumption afterillness. However, the interview times of themajority of the cases were within one weekand recall of water consumption prior toillness would still have been possible.Selection of cases and controls werestandardised during the study. All laboratoryconfirmed cases of residents in the two localauthorities were eligible and controls wereselected from the GP register using acomputerised programme in the HealthAuthority.

4) Response rate The number of cases in aprospective study can be unpredictable. Veryfew cases were encountered in the secondyear of the study, which coincided with theintroduction of general practitioner (GP)fund holding. There was no obviousexplanation for the low numbers, andenquiries did not reveal a decrease inlaboratory submissions at the time. A goodresponse rate (98%) was observed in thestudy. There were only 4 cases (2%) thatwere non-responders; of these one was arefusal; two were non-responders, and onecould not be interviewed. The goodresponse rate was primarily due to thepersistence of the RA’s in making contact athome, allowing for out of hours andweekend interviews. Face to face interviewswere preferred to telephone interviews orpostal questionnaires. In the study area,many homes do not have telephones andpostal questionnaires would be unlikely toachieve as high a response rate and could beincomplete [76].



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Excluded casesThe study was designed to examine primarycases of sporadic cryptosporidiosis and itsassociation with local risk factors. Infectedindividuals who had travelled abroad andsecondary cases due to person to personspread among household members wereexcluded. In the study, travel abroad andsecondary cases represented 6 (2.9%) and 36(17.4%) of the reported cases respectively. Inthe event of an outbreak, cases would also beexcluded; however, there were nocryptosporidiosis outbreaks during the periodof the study in Allerdale and Copeland. Aclustering of cases in spring of 1999 wasindependently investigated and found not tobe an outbreak. Despite many visitors to theLake District each year, there were very fewtourists among the reported cases. This couldbe due to under notification (althoughtourists had returned to their homes andreported illness to their own GPs.). Assporadic human cryptosporidiosis is not anotifiable disease, the mechanism fornotifying infection between districts wouldtherefore not apply to cryptosporidiosis. Incontrast, in the outbreak situation in southand west Devon, a significant proportion ofcases amongst tourists was recorded. [32].

Seasonal PeaksThe sporadic cases in the study demonstratedseasonal increases in the months of April, Mayand June with a smaller rise in September,October and November. These seasonalincreases were similar to those observed byother researchers [3, 6, 9, 55]. Casemorefound an association with the spring peak andnewborn lambs [77].

The local Veterinary Laboratories Agencyidentified an increase in Cryptosporidiumanimal isolations in the months of March,April and May (see section III: 3). However,laboratory animal isolations have to be viewed

with caution, as they are dependent onvoluntary submissions by farmers.

Age GroupThe majority of cases in the study werechildren under 16 years: 86 (57%) under 5years; 47 (31%) between 6 - 15 years; andonly 19 (12%) over 16 years. The median agewas two (range 0-5) in the 0-5 age group; nine(range 6-15) in the 6-15 age group; and 28(range 19-55) in the over 16 age group. Themean and median ages of all the cases waseight and four years respectively and rangedfrom 0 to 55 years of age. The commonest agegroup in the under fives was similar to thatseen in the England and Wales nationalsurveillance of laboratory reports conductedby the Public Health Laboratory Service [7]and also the 1990 PHLS study [9]. Themedian age of sporadic cases in the AustralianStudy was 11 years (range 0-81 years) inMelbourne and 10 years (range 0-83 years) inAdelaide respectively [75].

It was of note that the 1992 outbreak ofcryptosporidiosis in West Cumbria showedthe same concentration of cases amongstchildren and did not record a shift in the agedistribution to adults as was seen in someearlier UK outbreaks [78]. This could be dueto a high immunity among adults in the studyarea. Researchers have found that re-infectioncan result in milder symptoms [69]. In thecase of a working adult, it was possible thatthe GP was not consulted.

Symptoms and DurationThe cases demonstrated similar symptomsseen in many other studies; diarrhoea (threeor more loose stools in 24 hour period),abdominal pain and vomiting were mostcommon, followed by fever, loss of appetiteand weight loss. Thirty seven cases in thestudy had continuing symptoms. Themedian duration of illness in 115 cases was



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nine days (range 2-21). The mean andmedian duration in the study on adult humanvolunteers recorded 9 and 6.3 daysrespectively [67]. The Australian studyreported a mean duration of 22.4 days (range1-100) in Melbourne, and a mean duration of19.4 days (range 2-120) in Adelaide [75].The 1990 PHLS study recorded a meanduration of diarrhoea of 9 days (range 1 - 90)with the longest mean duration of 12 days ininfants and patients over 65 years and thelowest duration of 7 days in patients 15-24years [9].

Admissions to HospitalTwenty three (15%) of the primary cases inthis study were admitted to hospital. Twelve(52%) of those admitted were children undertwo years, which was also the median age ofall hospital admissions (range <1to14). The1992 cryptosporidiosis outbreak in WestCumbria recorded 8 hospital admissionsrepresenting 16% of the primary cases in theoutbreak or 10% of all reported cases at thetime.

The 1990 PHLS study reported 20% patientsidentified with cryptosporidiosis wereadmitted to hospital, but this was thought tobe related to extremes of age rather thanseverity of symptoms [9]. The AustralianStudy reported 14 (7%) cases admitted tohospital in Melbourne and 16 (11.9%) casesin Adelaide respectively [75]; however themedian ages of the Australian cases were olderthan this North Cumbria study.

Public Health MessagesThe results of this study serve to re-emphasiseimportant public health messages concerningcryptosporidiosis that had been promulgatedpreviously. Washing hands after visits tofarms before eating, remains important in theprevention of sporadic cryptosporidiosis. In1999, the Chief Medical Officer advised“boiling potable water” for specific groupsand immuno-compromised individuals in thenewsletter to general practitioners [79]. TheHealth and Safety Executive had also givenout prevention advice to farmers and thoseworking in farms [80, 81].

Other recommendationsThe UK Expert group on Cryptosporidium inwater supplies made wide-ranging recommen-dations following the review of the risks ofcryptosporidiosis in water [12, 17, 48]. Inaddition, new regulations were introduced in1999, [The Water Supply (Water Quality)(amendment) Regulations 1999], whichrequire water companies to conduct riskassessments for each of its treatment works toestablish whether a significant risk fromCryptosporidium oocysts exists in watersupplied from the works [82]. Where it isestablished that there is such a risk, the watercompany must use a process for treating thewater to ensure that the average number ofCryptosporidium oocysts per 10 litres of wateris less than one. The existing regulations andrecommendations should be furtherexamined in light of their application tosporadic cases in different locations.

In Year 2000, membrane filters were installedin the Ennerdale and Cornhow watertreatment works. The intervention studyexamined the effects on humancryptosporidiosis cases, after the installation.


Conclusion - Case-control Study

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Sporadic case-control Study

This study examined risk factors and inparticular, if there was a dose responserelationship between cases of cryptosporidio-sis and drinking unboiled tap water in tworural communities.

The results showed that the many of the caseswere children less than six years (median age=4 years). A highly significant association(p=0.001) was found between illness in casesand drinking unboiled tap water in all thewater supply zones in the study area. A dose-response relationship was also found, with theodds of illness increasing by approximately40% with each extra pint of unboiled tapwater consumed each day. The risk ofCryptosporidium infection throughconsuming unboiled tap water in all the watersupply zones was the same, irrespective ofwhether the water supply zones received waterfrom unfiltered, a variety of conventionallytreated and unfiltered, or private watersupplies.

There were also significant associationsbetween cases and short farm visits, contactwith farms, farm animals, animal faeces, othercontact with farm animals, stroking animals,and frequency of farm visits in the singlevariable analysis. Short farm visits remainedsignificant in the multi-variable analysis(p=0.04), together with frequency of farmcontact (p for trend =0.02).

Eating food within 1-2 hours of contact witha farm animal was found to be a significantrisk factor in the single variable analysis.Washing hands before eating, after visits to

farms, appears to protect against the infectionin the multivariable analysis that excludedmixed water supply.

Microbiological analysis of isolates of casesshowed that they were predominantlyCryptosporidium parvum genotype 2, thestrain with a wide host range, including farmanimals.

There are probably different risk factorsassociated with sporadic cryptosporidiosis indifferent locale. This study was conducted intwo rural localities with strong agriculturalconnections, encompassing arable and animalhusbandry, and plentiful wild life. Thisprospective, longitudinal case-controlledstudy has shown the value of detailedinvestigations in elucidating the risk factors,clinical and microbiological features ofsporadic cryptosporidiosis in an area ofroutine high incidence.

Conclusion


Discussion - Intervention Study

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Intervention Study

Prospective intervention studies, involvinglarge populations over long periods of time,are prone to many difficulties, not least thechange in the background ecology of thestudy area. Concerns regarding the quality ofpotable water in non-outbreak scenarioprompted some intervention studies in USAand Australia. In the main, these studiesexamined, points of use home filters [83].Home filters had previously been found to beprotective against cryptosporidiosis in theoutbreak in Milwaukee [84]. A recent studyshowed that home filters were also protectiveagainst sporadic cryptosporidiosis [85].Intervention studies had not previouslyexamined the effects of installation of filters atthe treatment works and the effects on theincidence of cryptosporidiosis. One studyexamined seorprevalence in a collegecommunity rather than incidence of disease,following the installation of filters at thetreatment works [86]. This is the firstintervention study in the UK to examine theeffects of newly installed membrane filters inwater processing works, on the incidence ofsporadic cryptosporidiosis.

The intervention study in North Cumbriawas conceived in 1997 when it transpired thatmembrane filters were to be commissionedfor the water supply zones of Ennerdale andCrummock, each covering approximately athird of the population. Originally scheduledfor 1999, installation and commissioning ofthe filters began on 1 March 2000 and wereoperational after 31 July 2000, in the twotreatment works of the Ennerdale andCrummock water supply zones. This delay

resulted in a shorter post-intervention periodthan planned; the completion date for thestudy had already been pre-determined as 31August 2002, in the protocol.

Data collection procedures remained the sameas for the case control study period.Prolongation of enrolment provided anopportunity to examine the impact of theinstallation, commissioning and operation ofMembrane Filtration in the populationsreceiving water from the Crummock andEnnerdale sources, compared with the samepopulations prior to the installation ofMembrane Filtration and also to thepopulation served by unchanged “other”water sources, which had been provided withconventionally treated and unfiltered waterthroughout the study periods (That is, before,during, and after installation of MembraneFiltration of the Crummock and Ennerdalesources).

The United Kingdom was struck by a severeepidemic of Foot and Mouth Disease inlivestock during 2001. The first and last caseswere diagnosed in weeks 8 and 39; the firstcase was recorded on 21 February 2001 andthe country was declared free of Foot andMouth on 21 January 2002. During theepidemic, a variety of policies was applied;notably mass slaughter of livestock, restrictionof public access to the countryside andrestriction of animal movements. Voluntarycontainment of animals from normal pastureswas also reported to have been common.Moreover, farms within a three mile radius ofthose infected were compulsorily quarantinedand even the unaffected ones adopted a siegestrategy.

Discussion



126

Children and members of the public werebarred from large areas of the countryside,and therefore had virtually no contact withfarm animals throughout the whole episode.

The Foot and Mouth Epidemic wereassociated with a substantial fall in nationalreporting of cryptosporidiosis, which wasmost marked in the North West Region,including Cumbria [87]. This area historicallyhad the highest rates of cryptosporidiosis inman and high sheep and cattle densities andwas particularly hard hit by the FMDepidemic and the control and containmentmeasures. The reasons for the decline inhuman cryptosporidiosis associated with theFMD epidemic cannot be deduced withcertainty, but would be consistent with lowerlevels of Cryptosporidium associated livestockfaecal contamination of water sourcescombined with reduction of human contactwith animals. The FMD epidemic isanticipated to cause a permanent change tothe ecology and economy of Cumbria.

This epidemic occurred during the plannedperiod of recruitment to the post intervention(post installation of Membrane Filtration)study. Interpretation of trends within thestudy population must therefore consider theimpact of the FMD epidemic as well as theimpact that may be explained by installationof Membrane Filtration.

Comparison of incidence rates in the preand post intervention periodA total of 175 cases were recruited to thestudy: 153 in the pre intervention period (1March 1996-29 February 2000) and 22 in thepost intervention period (1 March 2000-31August 2002). The annual incidence rateexceeded 10 per 100,000 in the preintervention period with a peak of over 35 per100,000 in 1999 to below 10 per 100,000 inthe post intervention period.

Examination of cases resident in the watersupply zones show approximately equalproportions in the pre intervention period:Crummock (56), Ennerdale (43) and“other”(54), and similar incidence rates. Inthe post intervention period, there was aproportional difference in the reduction inthe three water supply zones, with six cases inCrummock, three in Ennerdale and 13 in“other” water supply zones seen in the postintervention period. Additionally, PoissonRegression analysis was used to model theimpact of the introduction of membranefilters and the FMD in livestock on theincidence of human cryptosporidiosis usingthe unchanged “other” water sources receivinga variety of conventionally treated andunfiltered water as a reference within themodel. The analysis took into account thedifferent time periods: pre intervention, filtercommissioning, established filtration preFMD, established filtration and FMD andestablished filtration post FMD. The analysisshowed a significant differential decrease inthe incidence rates in Ennerdale andCrummock compared with the “other” watersupply zones, when data for the period duringand after the commissioning period (after 1March 2000) were studied (p=0.024). Thereduction in the unchanged “other” watersupply zone without membrane filtration waslikely to be due to the FMD epidemic alone.It is highly probable that the reduction seen inEnnerdale and Crummock which was morethan the “other” water zones was not only dueto FMD epidemic but was also due to thenewly installed membrane filters.

Risk factorsRisk factors of sporadic cryptosporidiosis hadalready been examined in the initial four-yearperiod, prior to the installation of membranefilters. Further analysis of the six and halfyears data was conducted applying single andmultivariable analyses, for the whole studyperiod. The results showed that drinking



127

unboiled tap water was again significantlyassociated with sporadic cryptosporidiosis(p<0.001).

Other risk factors were found to be contactwith cow and other farms (p=0.002), andfeeding pets leftovers (p=0.021). These resultswere mainly derived from the larger numberof cases in the pre intervention period.

Biases (1 March 1996-31 August 2002)Recall bias for the whole study period wouldbe minimal. Interviews of over 84% of thecases were completed within one week.Completion of the interviews of casestogether with three and more controls werecarried out within two weeks amongst over64% cases and their controls, and withinthree weeks for over 95% cases and theircontrols. The study achieved a 98% responserate overall with only five cases who refusedor could not be found. There were no localoutbreaks or increased publicity during thepost intervention period. Thereforeinformation bias or selection bias would alsobe minimal.

Cases and controls were not duplicated in thestudy. This created some difficulties in thefourth year in the age group under five insome areas of the study, when some generatedcontrols were found to be cases or controlsalready in the study. More controls had to begenerated; however, there were sufficientnumbers in the population pool in thecommunity for the controls required in thisresearch. Researchers embarking on lengthyprospective studies should be aware of thisissue.

Age Group and SexThe majority were under 16 years. Mean ageoverall was 9.1, median 4.0 (range <1 to 62).In the pre intervention period, the median agefor the cases was 4 and that for the postintervention was 8. Children less than fiveyears predominate in both time periods.

Symptoms and DurationSymptoms of diarrhoea and abdominal painpredominate in both periods. Thirty-eightcases (25%) in the pre intervention periodand four cases (18%) in the post interventionperiod had continuing symptoms, at the timeof interview. Of the remaining cases, themedian duration of illness was 9 days (range2-21) and 10 days (range 3-20) in the twotime periods respectively.

Admission to HospitalIn the pre intervention period, 23(15%) ofthe cases were admitted to hospital, and theirages ranged from 0-14 years with a mean andmedian age of 3.7 and 2 years respectively. Inthe post intervention period, three cases(14%) were admitted to hospital and theirages ranged from 3 to 12 years with a meanand median age of 8.3 and 10 yearsrespectively.

Seasonal variation A spring peak was apparent in cases between1996 and 2000 but was no longerconspicuous after 1 March 2000 to 31 August2002. This could well be the effects of theFMD outbreak and the installation ofmembrane filters in Ennerdale andCrummock water supply zones.

Genotype ResultsThe Reference Unit reported thatCryptosporidium parvum genotype 2remained the predominant group throughoutthe total period of the study. However therewere very few cases in the post interventionperiod. Genotype 2 is associated with humansand animals.

Effect on study areaThe draconian measures taken to contain andcontrol the spread of Foot and Mouthepidemic in livestock have resulted insubstantial reduction in total farm and animalpopulation in the study area. It is likely that



128

this will remain a confounding factor in anyfuture studies of sporadic cases of humancryptosporidiosis in Ennerdale andCrummock water supply zones. It will take along while before the impact of Foot andMouth recedes and the ecology of this part ofCumbria returns to conditions prevailingbefore the disaster, if ever.

Thus even prolonging the current studybeyond 31 August 2002 may not haveproduced more convincing results to reflectthe sole effects of the installation ofmembrane filters for the Ennerdale andCrummock water supply zones.

Unexpected events do indeed disrupt theoutcome of the best-laid plans of projects, asoccurred in this intervention study. TheWater Company had explored the efficiencyof the membrane filtration in removingCryptosporidium oocysts [88]; similarmembrane filtration technology had beenapplied in certain water treatment works inAustralia, United States of America and in theUK. The reduction of humanCryptosporidium infection through theinsertion of such filters in water treatmentworks in a rural setting and over a shortperiod, has been demonstrated by this study.Confirmation of this would have to bedetermined by other studies and perhaps inother locations.


Conclusion - Intervention Study

129

Intervention Study

This study examined the impact of theinstallation of membrane filters on theincidence of Cryptosporidium infection in tworural communities in North Cumbria, wherenew membrane filters were installed in twowater supply zones and compared the resultswith the rest of the “other” water zones thatdid not have major changes in the treatmentworks during the course of the study.

During the study period, in 2001 until early2002, Foot and Mouth disease (FMD)occurred in animals in the study area. Manyanimals were killed and people were bannedfrom visiting farms and large parts of thecountryside. The study results show that inthe post filtration period, there was a veryclear reduction in the incidence of sporadiccryptosporidiosis in the whole study area. Themost likely cause of this reduction was theFMD epidemic and the attendant control andcontainment measures adopted. This wouldhave applied equally to all the different watersupply zones. However, there was asignificantly greater reduction in theincidence rates in the Crummock andEnnerdale water zones, which had newmembrane filters when compared with the“Other” supply zones that did not. Thus,despite the confounding effect of the FMDepidemic, the statistically significantdifferential decrease in the incidence ofsporadic cryptosporidiosis in the Ennerdaleand Crummock water zones could probablybe attributable to the installation ofMembrane Filters (p=0.024).

Risk factor analysis again showed drinkingunboiled tap water to be highly significantlyassociated with infection overall (p<0.001).Risk was not significantly different betweenthe different water supply zones. Other riskfactors were found to be contact with cow andother farms (p=0.002), and feeding petsleftovers (p=0.021).

Microbiological analysis on the isolates for thewhole study period, consistently showedCryptosporidium parvum genotype 2 to bepredominant for the six and half years, and inthe two time periods. The differentialpredominance of genotype 2 over genotype 1(the human strain) suggests zoonotictransmission.

Conclusion


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51. Hunter P, Syed Q, Naumova EN. Possibleundetected outbreaks of cryptosporidiosis in areasof the North West of England supplied by anunfiltered surface water source. Commun DisPublic Health 2001; 4(2): 136-8.

52. The Outbreak Control Team. Cryptosporidiumoutbreak. Spring 1992. West Cumbria HealthAuthority 1992.

53. Dean AG, Dean JA, Coulombier D, Brendal KA,Smith DC, Burton AH, Dicker AC, Sullivan K,Fagan RF, Arner TG. Epi Info, Version 6: a wordprocessing, database, and statistics program forepidemiogology on microcomputers, Centers forDisease Control and Prevention, Atlanta, Georgia,U.S.A., 1994.


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54. Francis B, Green M, Payne C (eds.). The GLIMSystem Release 4 Manual, 1993, Clarendon Press,Oxford.

55. Thomson MA, Benson JWT, Wright PA. Two yearstudy of Cryptosporidium infection. Arch Dis Child 1987; 62: 559 - 63.

56. Scott CA, Smith HV and Gibbs HA. Excretion ofCryptosporidium parvum oocysts by a herd of beefsuckler cows. Vet Rec (1994); 134: 174.

57. National Cryptosporidium Survey Group. A surveyof Cryptosporidium oocysts in surface andgroundwaters in the UK. Journal of the Instituteof water and Environmental Management 1992;6:697-703.

58. Finch GR, Black EK, Guyrek L, Belosevic M.Ozone inactivation of Cryptosporidium parvum indemand-free phosphate suffer determined by invitro excystation and animal infectivity. Appl Environ Microbiol 1993; 59: 4203-10.

59. Korich DG, Mead JR, Mladore Ms, Sinclair NA,and Sterling CR. Effects of ozone, chlorinedioxide, chlorine and monochlorine onCryptosporidium parvum oocysts viability, ApplEnviron Microbiol 1990; 56:1423-8.

60. Ransome ME, Carrington EG, Whitmore TN andHarman SA. Evaluation of the efficiency ofalternative disinfectants to chlorine. (Report DoE 3143) Medmenham WRc.

61. Le Chevallier MW, Norton WD, Lee RG. Giardiaand Cryptosporidium spp in filtered drinking watersupplies. Appl Environ Microbiol 1991; 57:2617-21

62. Smith HV, Grimason AM, Benton C, Parker JFW.The occurrence of Cryptosporidium spp oocysts inScottish waters and the development of afluorogenic viability assay for individualCryptosporidium spp oocysts. Water science andtechnology 1991; 23(2): 169-72.

63. Quennell S (in press). Review of Cryptosporidiummonitoring data in the UK. In West PA, andSmith MS Editors. Proceedings of workshop ontreatment optimisation for Cryptosporidiumremoval from water supplies. London HMSO.

64. Rose J, Gerba C and Jackubowski W. Survey ofportable water supplies for Cryptosporidium andGiardia. Environmental Science and Technology1991; 23:1393-1400.

65. Gregory J, Ives KJ, Scott JE, Manjuolo DB.Removal of Cryptosporidium oocysts by watertreatment methods or laboratory seals. [Finalreport to the Department of the Environmental1991].

66. Hall T, Pressdee J, Carrington EG. Removal ofCryptosporidium oocysts by water treatmentprocesses. [Report FR 0457]. Marlow:Foundation for water research.

67. Dupont HL, Chappell CL, Sterling CR, OkhuysenPC, Rose JB, Jakubowski W. The infectivity ofCryptosporidium parvum in healthy volunteers. N Eng J Med. 1995; 332:855-9.

68. Okhuysen PC, Chappell CL, Crabb JH, SterlingCR, Dupont HL. Infectivity of three distinctCryptosporidium parvum isolates for healthy adults.J. Infect Dis 1999; 180:1275-81.

69. Okhuysen PC, Chappell CL, Sterling CR,Jakubowski W, Dupont HL. Susceptibility andserologic response of healthy adults to reinfectionwith Cryptosporidium parvum. Infect Immun.1998; 66:441-3.

70. McLauchlin J, Pedraza-Diaz S, Amar-HoetzenederC, and Nichols GL. Genetic characterisation ofCryptosporidium strains from 218 patients withdiarrhoea diagnosed as having sporadic cryp-tosporidiosis. J Clin Microbiol 1999; 37(10):3153-8.

71. McLauchlin J, Amar C, Pedraza-Diaz S, NicholsGL.Molecular Epidemiological analysis ofCryptosporidium spp in the United Kingdom:Results of genotyping Cryptosporidium spp in 1705foecal samples from Humans and 105 faecalsamples from livestock animals. J Clin Microbiol2000; 38 (11): 3984-90.

72. Chalmers R, Elwin K. Implication andimportance of genotyping Cryptosporidium.Commun Dis Public Health 2000; 3(3): 155-7.

73. Patel S, Pedraza-Diaz S, McLauchlin J, CasemoreDP, Outbreak Control Team South and WestDevon 1995, et al. Molecular characterisation ofCryptosporidium parvum from two large waterborneoutbreaks. Commun Dis Public Health 1998;1:231-3.

74. Casemore DP, Wright SE, Coop RL.Cryptosporidiosis - human and animalepidemiology. In Fayer R. ed. Cryptosporidium andcryptosporidiosis. New York, London, Toyko,CRC Press 1997: 65-92.

75. Robertson B, Sinclair MI, Forbes AB et al. Casecontrol studies of sporadic cryptosporidiosis inMelbourne and Adelaide, Australia. EpidemiolInfect 2002; 128: 419-31.

76. Smeeth L, Fletcher AE. Improving the responserate to questionnaires. BMJ 2002; 324:1168-9.

77. Casemore DP. Cryptosporidiosis another source.BMJ 1989; 298:750-1.


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78. Maguire HC, Holmes E, Hollyer J, et al. Anoutbreak of cryptosporidiosis in south London:what value the p value? Epidemiol Infect 1995;115 (2): 279-87.

79. Chief Medical Officer. Cryptosporidium in water:advice to the immocompromised. CMO’s update21 1999, DoH, London.

80. Health and Safety Executive (HSE) InformationSheet No. 2. Common zoonoses in agriculture.Health and Safety Executive, London, UK.

81. Health and Safety Executive (HSE). InformationSheet No. 19. Occupational Health risks fromcattle. Health and Safety Executive, London, UK.

82. Department of the Environment, Transport andthe Regions. Statutory Instrument 1999 no 1524.Water Industry, England and Wales. The Water Supply (Water Quality) (Amendment)Regulations 1999.

83. Payment P, Hunter PR. Intervention studies inDrinking water and Infectious Diseases 2002;CRC Press LLC.

84. Addiss DG, Pond RS, Remshak M, Juranek DD,Stokes S, Davis JP. Reduction of risk of waterydiarrhoea with point - of - use water filters duringa massive outbreak of waterborne Cryptosporidiuminfection in Milkwaukee, Wisconsin, 1993. Am JTrop Med Hyg 1996; 54 (6): 549-53.

85. Calderon R and Craun G. CommunityIntervention Study for estimation of endemicwaterborne disease. Epidemiology 2000; 11:414.

86. Frost FJ, Muller T, Calderon RL, Craun GF. Aserological survey of college students for antibodyto Cryptosporidium before and after filtration plantEpidemiol Infect 2000; 87:125.

87. Smerdon WJ, Nichols T, Chalmers RM, Heine H,Reacher M. Foot and Mouth Disease in livestockand reduced cryptosporidiosis in Humans, Englandand Wales. Emerg Infect Dis 2000; 8 (1); 22-28.

88. USF. Memcor. Membrane technology for potablewater treatment. Information pack provided byUnited Utilities plc. Ltd.


Section IIMicrobiology


1. Local Arrangements

In North Cumbria, during the study period,all faecal samples submitted by generalpractitioners are routinely screened forCryptosporidium spp. regardless of age of thepatient, at the Carlisle Public HealthLaboratory and the Furness GeneralMicrobiology Laboratory. West CumberlandHospital Microbiology Laboratory carried outroutine tests for Cryptosporidium spp insemi-formed and liquid faecal samples of allage groups submitted to the Laboratory. Priorto 31 December 1998, isolates were sent tothe PHLS Cryptosporidium Reference Unit(CRU) at Rhyl for confirmation since March1996 and PHLS Food Safety Laboratory,Colindale for genotyping. After 1 January1999, confirmation and genotyping werecarried out at CRU, Swansea.

2. Method

A. Local Laboratory DiagnosticMethods

Carlisle Public Health LaboratoryAll faecal specimens arriving in thelaboratory are routinely examined forCryptosporidium oocysts, apart from thosespecifically requesting individualinvestigations only (e.g. Clostridiumdifficile).

From the beginning of this study themethod used for identification ofCryptosporidium spp., was to air dry asmear of faeces on a clean microscopeslide. This was stained with auramine

phenol and counterstained with carbolfuchsin [1]. In May 1999 the counterstainwas replaced with 0.1% potassiumpermanganate [2].

In both cases, positives were confirmed bythe modified Ziehl-Neelsen stain method[3] and, for the duration of this study, allpositive samples were sent to theCryptosporidium Reference Unit forconfirmation and typing.

West Cumberland Hospital LaboratoryThroughout the study the method usedfor identification of Cryptosporidium spp.,has been the modified Ziehl Neelsenmethod.

A smear of faeces was placed on a cleanmicroscope slide, air dried and then fixedin methanol for three minutes. Onremoval from, and evaporation of, themethanol, the slide was flooded withstrong carbol fuchsin and left for 15minutes. The slide was then rinsedthoroughly and repeatedly with 3% acidalcohol until colour no longer floods fromthe smear. It was then rinsed with tapwater and counter-stained with 0.5%malachite green for 30 seconds.

After rinsing and blotting dry, the slidewas read using bright field microscopy.Cryptosporidium spp. oocysts appeared asbright pink spherical bodies against agreen background.

SECTION II

Microbiology


Microbiology

137

Furness General MicrobiologyLaboratoryThe same method was used throughoutthe study period.

A thin faecal smear was prepared on a glassmicroscope slide. This was allowed to airdry before fixing in absolute methanol for3 minutes. The slide was flooded withpre-filtered (paper filter) auramine phenoland left for 10-15 minutes. This was thenwashed with tap water and counterstainedwith strong carbol fuchsin for 10 seconds.The slide was then washed with tap wateragain and allowed to dry. The slide wasthen examined on a UV microscope,using a low power (x 40) objective lens[4].

B. Cryptosporidium Reference Unit(CRU)

Confirmation and typing ofCryptosporidium isolates

Confirmation : [1 March 1996 - 31 December 1998 -Rhyl CRU1 January 1999 - 31 August 2002 -Swansea CRU]

To confirm the identification ofCryptosporidium at the CryptosporidiumReference Unit, faecal smears were stainedusing a modified Ziehl-Neelsen stain [3]and inspected by bright field microscopy,or using an auramine phenol method [5]and inspected by fluorescence microscopy.Equivocal results were confirmed by animmunofluorescent antibody test (TCSWater Sciences, Buckingham, UK)according to the manufacturer’sinstructions.

Genotyping

a) Prior to 31 December 1998 - PHLSFood Safety and MicrobiologyLaboratory, Colindale, London

DNA extraction/amplification

Oocyst disruption and DNA purificationwas performed using a modification ofmethods previously described. In reactiontubes approximately 100µL of wholefaeces was added to 900µL of lysis bufferL6 (10 M guanidinium thiocyanate, 0.1M Tris-hydrocholoride pH 6.4, 35mMEDTA pH 8, 2% (w/v) Triton X-100) and0.3g of 0.1mm diameter zirconia beads(Stratech Scientific, Luton, UK). Thetubes were then shaken in a Mini-Beadbeater (Stratech Scientific) for 2 minat maximum speed and left at roomtemperature for 5 min before beingcentrifuged at 12 000g for 15s. Theparticulate material was discarded and40µL of coarse activated silica suspensionadded. The suspension was mixed in avortex mixer and allowed to stand at roomtemperature for 10 min and, aftercentrifugation (as above), the supernatantwas discarded. The pellet was washed bycentrifugation twice with 200µL of L2washing buffer (10M guanidiniumthiocyanate, 0.1 M Tris-hydrochloride),once with 200µL of ice cold 80% ethanol,and once with 200µL of acetone. Theacetone was discarded and the pellet driedat 55°C for 5 min. 100µL of water wasadded and after vortexing briefly,incubated at 55°C for 10 min. The tubewas then centrifuged for 1-2 min at 12000g and the supernatant (DNA sample)either used directly for PCR amplificationor stored at -20°C until further use [6].


Microbiology

138

b) 1 January 1999 to 31 August 2002(Swansea CRU)

Prior to DNA extraction, oocysts werepurified from the faeces using saltflotation [7]. Briefly, the oocysts wereseparated by flotation from faecal debrisusing saturated salt solution andcentrifugation for 8 minutes at 1600xg.The floated material containing theoocysts was washed with de-ionisedoocyst-free water, the oocysts resuspendedin 1ml deionised, oocyst-free water andstored at +4oC prior to use. To extractDNA, 200µl oocyst suspension wasincubated at 100ºC for 60 minutes andDNA extracted using proteinase Kdigestion in lysis buffer at 56ºC and aspin-column filtration technique (QiAMPDNA mini kit, Qiagen, Crawley, UK).DNA extracts were stored at -20oC priorto use.

The genotype of the CryptosporidiumOuter Wall Protein (COWP) andthrombospondin related adhesive protein(TRAP-C2) genes were investigated usingPCR-RFLP [8,9]. Briefly, primers cry15and cry9 were used to amplify a 553 basepair region of the COWP gene, which wasthen subjected to restriction endonucleasedigestion by RsaI (Promega,Southampton, UK). Primers for theTRAP-C2 gene were designed for a nestedPCR [10] and subjected to restrictionenzyme digest with HaeIII and BstEII(Promega, Southampton, UK).

The digestion products were separated byagarose (3% w/v) gel electrophoresis andthe product size was confirmed bycomparison with a DNA molecularweight standard marker (LifeTechnologies, Glasgow, UK). Thedigested products were visualised usingethidium bromide (0.1mg/100ml) andrecorded using a digital camera and

KDS1D analysis software (Kodak,Rochester, NY, USA).

All procedures were subject to internaland external quality control, withpreviously characterised positive andnegative control material included in eachprocessing batch.

3. Microbiological Results

A. Confirmation

All the specimens submitted from thisstudy and examined by theCryptosporidium Reference Unit wereconfirmed to be Cryptosporidium parvum.

B. i) Sporadic cryptosporidiosiscase-control study 1 March 1996 - 29 February2000

Genotype results 1 January 1998 - 29February 2000 (Tables 1, 2, 3)

Local laboratories reported a total of 101cases of cryptosporidiosis during thisperiod. Sixty-seven (66%) isolates weresent to the Reference Unit. Genotypeanalysis showed 56 isolates (84%) wereCryptosporidium parvum genotype 2; oneisolate (1%) was Cryptosporidium parvumgenotype 1, and 10 isolates (15%) wereuntypeable [Table 1]. Genotype 2 wasthus the most common genotype in all agegroups [Table 2]. The one genotype 1isolate was from an adult case inCopeland.

Comparison of genotype between theexcluded and primary included cases didnot show any marked differences, asgenotype 2 remained the most commongenotype in all the different casecategories [Table 3].


Microbiology

139

ii) Intervention Study 1 March1996 - 31 August 2002

[Pre intervention = 1 March 1996 - 29 February 2000][Post intervention = 1 August 2000 - 31 August 2002][Commissioning = 1 March 2000-31 July 2000]

Genotype results 1 January 1998 - 31August 2002 (Tables 4, 5, 6)

The local laboratories reported 124 casesof Cryptosporidium between 1 January1998 and 31 August 2002. Eighty-four(68%) isolates were sent to the ReferenceUnit. Analysis of the isolates showed 70(83%) were Cryptosporidium parvumgenotype 2, four (5%) wereCryptosporidium parvum genotype 1, and10 (12%) were untypeable [Table 4].Genotype 2 remained the most commongenotype in all the different age groups[Table 5]. Of the four genotype 1 cases,three were adults (two from Copeland andone from Allerdale) one was a child in the6-15 age group from Allerdale.

The post intervention period showed amarked decrease in total and primaryCryptosporidium cases, compared to thepre intervention period [Table 5]. In thepre intervention period, 68 (67%) isolateswere sent to the Reference Unit, andcontrasts with 14 isolates (78%) in thepost intervention period. The two isolatesin the commissioning period weregenotype 2; this was also the mostcommon genotype in both time periods:57 (84%) in the pre intervention period,and 11 (79%) in the post interventionperiod. Comparison of the genotypeswithin the different age groups showedthat genotype 2 predominate in all agegroups in the pre intervention period,

with only one genotype 1 in an adult. Inthe post intervention period, of the fourisolates examined in the adults, two weregenotype 1 and two were genotype 2(50% each). One other genotype 1 waspresent in a child in the 6-15 year agegroup. Genotype 2 remained thedominant group in this period. It was alsonoted that the number of isolatesexamined in the post intervention periodwas small.

Comparisons of genotype amongst caseswith different case definitions (theexcluded cases and included primarycases) showed the same predominance ofgenotype 2 in both groups in the two timeperiods [Table 6]. Five genotype 1 casesthat had travelled abroad (amongst theexcluded group) in the post interventionperiod were local residents who were partof the Cryptosporidium outbreak inMajorca. The isolates of secondary cases inthe pre intervention period wereidentified as predominantly genotype 2;no genotype 1 isolates were identified inthis group. Unfortunately, no isolates ofsecondary cases were received at theReference Unit in the post interventionperiod for comparisons to be made.

4. Discussion

Cryptosporidium parvum genotype 2 hasbeen identified as the strain with a broadhost range including animals and man,and contrasts with genotype 1, which islargely restricted to humans [6,11-13].The genotype results suggest thatinfection in majority of cases in the NorthCumbria study was primarily genotype 2,the zoonotic strain, and only four caseswere infected by genotype 1, the humanstrain.


Microbiology

140

YEAR Month

January

February

March

April

May

June

July

August

September

October

November

December

Total 15 (39%) 23 (61%) 1 (4%) 0 (0%) 22 (96%) 23 (100%)

January

February

March

April

May

June

July

August

September

October

November

December

Total 18 (30%) 43 (70%) 9 (21%) 0 (0%) 34 (79%) 43 (100%)

January

February

Total 1 (50%) 1 (50%) 0 (0%) 1 (100%) 0 (0%) 1 (100%)

Cummulative

Total 101 (100%) 34 (34%) 67 (66%) 10 (15%) 1 (1%) 56 (84%) 67 (100%)

0 1 0 1

0 0 0 0

0 0 0 0

0 0 0 0

0 0 2 2

0 0 1 1

0 0 0 0

1 0 3 4

3 0 6 9

3 0 11 14

2 0 9 11

0 0 0 0

0 0 2 2

0 0 0 0

1 0 0 1

0 0 1 1

0 0 2 2

0 0 0 0

0 0 2 2

0 0 1 1

5 5

0 0 8 8

0 0

0 0 3 3

0 0

0 0 0 0

0 1

Untypeable

(% of total

genotype)

Genotype 1

(% of total

genotype)

0 0

0 0

0 0

1 2

0 1

2 2

0 0

2 8

2 1

3 3

2 5

1 0

1 0

0

2

2

3

1

0

61

11

5

1

3

3

0

13

21

1

38

0

4

0

3

1

Genotype results (2)Case analysis (1)

Number of

primary

cases (100%)

1

Number not

sent to Swansea

(% of total

cases)

Cases sent

to Swansea

( % of total

cases)

1 0

Genotype 2

(% of total

genotype)

Total

(100%)

Year

1998

Year

2000

Year

1999

1

1

6

7

10

3

0 0

1 2

0 0

2 11

7 14

2 9

1

1 2

1 4

1 0

0 0

1 1

1 0

0 0

2

N.B. Table does not show 51 primary cases before routine genotyping began on 01/01/1998

NOTES

Definitions

2) Untypeable = No genotype identified

1) Cases = Primary cases incorporated into the study, discounting exclusions

Sporadic Cryptosporidiosis Case - Control Study1 March 1996 to 29 February 2000

TABLE 1 CRYPTOSPORIDIUM GENOTYPE RESULTS BY MONTH FROM CRYPTOSPORIDIUMREFERENCE UNIT (CRU)


Microbiology

141

Sp

ora

dic

Cry

pto

spo

rid

iosi

s C

ase

-Co

ntr

ol

Stu

dy

1 M

arc

h 1

99

6 t

o 2

9 F

ebru

ary

20

00

Case

s in

stu

dy (

1)

nn

(%)

n(%

tota

l)n

(% t

ota

l)n

(% t

ota

l)n

(100%

)

0 t

o 5

56

36

(64)

5(1

4)

0(0

)31

(86)

36

(100)

6 t

o 1

532

22

(69)

2(9

)0

(0)

20

(91)

22

(100)

16+

13

9(6

9)

3(3

3)

1(1

1)

5(5

6)

9(1

00)

Tota

l101

67

(66)

10

(15)

1(1

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(84)

67

(100)

N.B

.

1)

Table

does n

ot

show

51 p

rim

ary

cases t

hat

occurr

ed b

efo

re r

outi

ne g

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pin

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om

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1/0

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Gro

up

Un

typ

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Cryp

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m R

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ence

Un

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CR

U)

Case

s se

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to

CR

U (

%)

Pri

mary

case

sG

enoty

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(N

um

ber

(n

), %

of

tota

l p

rim

ary

case

s b

y a

ge

ban

d)

Typ

e 2

Tota

l

Ta

ble

2

Co

mp

ari

son

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ag

e g

rou

ps

& g

eno

typ

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Spor

adic

Cry

ptos

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dios

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ase

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ol S

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1 M

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6 to

29

Feb

ruar

y 20

00

Cry

ptos

pori

dium

geno

type

res

ults

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m C

rypt

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ridi

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t (C

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TA

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PAR

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YA

GE

GR

OU

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EN

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YP

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Microbiology

142

Contact with a confirmed case

Away from study area for more than 7 days

Visitor to area

Lives outside study area

Non responder

Refused to participate

Not interviewed/Social reasons

Interviewed previously

Dual infection

Dual infection and been abroad

No diarrhoea

Definitions

1) Primary cases = Primary index cases included in the study.

3) Case abroad = Case excluded due to being abroad in the 14 days before illness

4) Other cases= Cases excluded for the following reasons;

2) Secondary cases = Cases excluded from study due to contact with a member of their household with diarrhoea or

cryptosporidiosis in the 14 days prior to the onset of the secondary cases illness (Excludes cases excluded for other reasons).

Cases in

study

n (1) n (%) n (% total) n (% total) n (% total) n (100%)

Primary Cases (1) 101 67 66% 10 15% 1 1% 56 84% 67 100%

Secondary Cases (2)27 19 70% 5 26% 0 0% 14 74% 19 100%

Case Abroad (3) 5 5 100% 0 0% 0 0% 5 100% 5 100%

Other Cases (4) 10 8 80% 2 25% 1 13% 5 63% 8 100%

Total 143 99 69% 17 17% 2 2% 80 81% 99 100%

N.B.

1) Table does not show 51 primary & 13 excluded cases that occurred before routine genotyping commenced on 01/01/1998

Case type

(See definitions) Type 2 Total

Genotype results

Cases sent to

CRUUntypeable Type 1

Cases

Sporadic Cryptosporidiosis Case Control Study 1 March 1996 to 29 February 2000

Cryptosporidium genotype results from Cryptosporidium Reference Unit (CRU)

TABLE 3 COMPARISON BETWEEN CASES DEFINITIONS AND GENOTYPES.


Microbiology

143

Cry

pto

spori

dio

sis

Inte

rven

tion

Stu

dy 1

Marc

h 1

996 t

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January

January

Febru

ary

Febru

ary

Marc

hM

arc

h

Apri

lA

pri

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May

May

June

June

July

July

August

August

Septe

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Septe

mber

Octo

ber

Octo

ber

Novem

ber

Novem

ber

Decem

ber

Decem

ber

Tota

l15

(38%

)24

(62%

)1

(4%

)0

(0%

)23

(96%

)24

(100%

)T

ota

l1

(17%

)5

(83%

)0

(0%

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(40%

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(60%

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(100%

)

January

January

Febru

ary

Febru

ary

Marc

hM

arc

h

Apri

lA

pri

l

May

May

June

June

July

July

August

August

Septe

mber

Septe

mber

Octo

ber

Octo

ber

Novem

ber

Novem

ber

Decem

ber

Decem

ber

Tota

l18

(30%

)43

(70%

)9

(21%

)0

(0%

)34

(79%

)43

(100%

)T

ota

l0

(0%

)6

(100%

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(17%

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Tota

l124

(100%

)40

(32%

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(68%

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(12%

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(5%

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(83%

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)

January

Febru

ary

Marc

h

Apri

l

May

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July

N.B

. T

ab

le d

oes

not

show

51 p

rim

ary

case

s b

efore

rou

tin

e gen

oty

pin

g b

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on

01/0

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998

August

Septe

mber

Octo

ber

Novem

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Decem

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Tota

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(50%

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(50%

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(0%

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(83%

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(100%

)

Gen

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2

(% o

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tal

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Tota

l

(100%

)

Nu

mb

er

not

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t to

Sw

an

sea

(% o

f to

tal

case

s)

Case

s se

nt

to S

wan

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( %

of

tota

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t yp

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(% o

f to

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ore

-vali

dati

on

conducte

dJune

2002

result

ing

in2

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gre

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ssif

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from

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00

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2

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6

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88

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0

63

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00

0

Nu

mb

er

of

pri

mary

case

s

(100%

)

Nu

mb

er

not

sen

t to

Sw

an

sea

(% o

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resu

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by m

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it (

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aly

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U)


Microbiology

144

Case

s

in

stu

dy

(1)

Case

s

in

stu

dy

(1)

nn

(%)

n(%

tota

l)n

(%

tota

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(%

tota

l)n

(100%

)n

n(%

)n

(%

tota

l)n

(%

tota

l)n

(%

tota

l)n

(100%

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0 t

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(65)

5(1

4)

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85

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(100)

65

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68

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Microbiology

145

Cases

in

study

Cases

in

study

n (1) n (%) n(%

total)n

(%

total)n

(%

total)n (100%) n (1) n (%) n

(%

total)n

(%

total)n

(%

total)n (100%)

Primary Cases (1) 102 68 67% 10 15% 1 1% 57 84% 68 100% 18 14 78% 0 0% 3 21% 11 79% 14 100%

Secondary Cases (2) 27 19 70% 5 26% 0 0% 14 74% 19 100% 2 0 0% 0 0% 0 0% 0 0% 0 100%

Case Abroad (3) 6 6 100% 0 0% 1 17% 5 83% 6 100% 7 5 71% 0 0% 5 100% 0 0% 5 100%

Other Cases (4) 8 6 75% 2 33% 0 0% 4 67% 6 100% 4 1 25% 0 0% 0 0% 1 100% 1 100%

Total 143 99 69% 17 17% 2 2% 80 81% 99 100% 31 20 65% 0 0% 8 40% 12 60% 20 100%

UntypeableCases sent

to CRUType 1 Type 2 Total

p g yp p y

Case type

(See definitions)

Pre-intervention period for routine genotyping

1 January 1998 to 29 February 2000Post-intervention period 1 August 2000 to 31 August 2002

Cases Genotype results

Cases sent

to CRUUntypeable Type 1

Cases

Type 2 Total

Genotype results

Contact with a confirmed caseVisitor to areaLives outside study areaNon responderRefused to participateNot interviewed/Social reasonsInterviewed previouslyDual infectionDual infection and been abroadNo diarrhoea

N.B1) Does not show 51 primary & 13 excluded cases that occurred before routine genotyping commenced on

01/01/1998Re-validation conducted June 2002 resulting in 2 cases being re-classified from �Other cases� to �Primary Cases� (one genotype 2, pre-intervention and one not sent to CRU for genotyping, post-intervention) and one case re-classified from �Other cases� to �Case Abroad� (one genotype 1)

In addition, table does not show the 4 primary and 7 secondary cases that occurred in the filter commissioning period 01/03/2000 to 31/07/200

Definitions1) Primary cases = Primary index cases included in the study.2) Secondary cases = Cases excluded from study due to contact with a member of their household with

diarrhoea or cryptosporidiosis in the 14 days prior to the onset of the secondary cases illness (Excludes cases excluded for other reasons)

3) Case abroad = Case excluded due to being abroad in the 14 days before illness4) Other cases= Cases excluded for the following reasons;

Cryptosporidiosis Intervention Study 1 March 1996 to 31 August 2002

Cryptosporidium genotype results from Cryptosporidium Reference Unit (CRU)

TABLE 6 COMPARISON BETWEEN CASE DEFINITIONS AND GENOTYPES FOR DEFINEDPERIODS OF THE STUDY


References

146

Microbiology References

1. Casemore DP, Armstrong M, Sands RL.Laboratory diagnosis for cryptosporidiosis: J Clin Pathol 1985; 38: 1337-41.

2. Nichols G and Thom BT. Screening forCryptosporidium in stools: Lancet 1984; i: 735.

3. Anon. Standard operating procedure for theinvestigation of specimens other than blood forparasites. PHLS B.SOP 31. Technical ServicesPHLS HQ London 1998.

4. Diagnostic Parasitology manual - LiverpoolSchool of Tropical Medicine.

5. Casemore DP. Broadsheet 128: Laboratorymethods for diagnosing cryptosporidiosis. J Clin Pathol 1991; 44: 445-451

6. Patel S, Pedraza-Diaz S, McLauchlin J, CasemoreDP, Outbreak Control Team South and WestDevon 1995, et al. Molecular characterisation ofCryptosporidium parvum from two largewaterborne outbreaks. Commun Dis PublicHealth 1998;1:231-3.

7. Ryley JF, Meade R, Hazelhurst J, Robinson TE.Methods in coccidiosis research: separation ofoocysts from faeces. Parasitology 1976; 73: 311

8. Spano F, Putignani L, McLauchlin J, CasemoreDP, Crisanti A. PCR-RFLP analysis of theCryptosporidium wall protein (COWP) genediscriminates between C. wrairi and C. parvum,and between C. parvum isolates of human andanimal origin. FEMS Microbiology Letters 1997;150: 207-217.

9. Peng MM, Xiao L, Freeman AR, Arrowood MJ,Escalante AA, Weltman AC, Ong CSL,Mackenzie WR, Lal AA, Beard CB. 1997.Genetic polymorphism among Cryptosporidiumparvum isolates: Evidence of two distinct humantransmission cycles. Emerging Infectious Diseases1997; 3: 567-573.

10. Elwin K, Chalmers RM, Roberts R, Guy EC,Casemore DP, in press. The modification of arapid method for the identification of gene-specific polymorphisms in Cryptosporidiumparvum, and application to clinical and epidemiological investigations. Applied andEnvironmental Microbiology 2001; 67. 5581-5584

11. McLauchlin J, Pedraza-Diaz S, Amar-Hoetzeneder C, and Nichols GL. Geneticcharacterisation of Cryptosporidium strains from218 patients with diarrhoea diagnosed as havingsporadic cryptosporidiosis. J Clin Microbiol1999; 37(10):3153-8.

12. McLauchlin J, Amar C, Pedraza-Diaz S, NicholsGL. Molecular Epidemiological analysis ofCryptosporidium spp in the United Kingdom:Results of genotyping Cryptosporidium spp in1705 foecal samples from Humans and 105 faecalsamples from livestock animals. J Clin Microbiol2000; 38 (11):3984-90.

13. Chalmers R, Elwin K. Implication andimportance of genotyping Cryptosporidium.Commun Dis Public Health 2000; 3(3): 155-7.


Section IIIBackgroundInformation

In Study Area


Topography

The study area comprises the western “half ”of the County of Cumbria. The county is oneof diverse landscapes, which reflect a complexgeology. A central ‘dome’ of high relief thatforms most of the Lake District National Parkdominates the physical geography ofCumbria. Sixteen lakes fall within this areaand many of the county’s rivers originate fromhere and radiate outwards.

A substantial part of the county lies above 300metres and this mass of land physically dividesthe county from north to south and east towest. Cumbria is the second largest ShireCounty in England and contains almost halfof the whole land area of the North Westregion (48%).

Settlement pattern and populationin the study area.

This pattern has been dictated principally bythe area’s unique topography. The county’scentral high land of fells and mountains formsthe eastern edge of the area and is a naturalbarrier to cross-county communication andonly scattered populations live there.

Figure 1, based on the Governments standardcategories of ward level population density(sparsity bands) used in the distribution ofrevenue support to local authorities, illustratesthis feature. The map has been overlain withthe water supply details described in sectionIII, part A, illustrating that the majority of the

area’s population and settlements are locatedaround the periphery, on lower lying land onthe coastal plain.

The population is very dispersed; the majorityof settlements (more than 70%) contain lessthan 200 people. Workington (pop. 24810)in the Allerdale Borough Council area andWhitehaven (pop. 24880) in CopelandBorough Council area are the largest centresof population. The other urban areapopulations are,

TABLE 1 URBAN AREAPOPULATION ESTIMATES

IN ALLERDALE AND COPELAND 2001

Population estimates. Source CumbriaCounty Council briefing 05/02 based on2001 Census data [1]Seewww.cumbria.gov.uk/briefings/2002/brf0502.pdf

Generally, the population of the area hasremained relatively stable over the course ofthe study with a small decline in birth rateevident in the 0 to 5 age band series and bothareas having a small net migration of residentsout of each area, mainly from the two mainurban areas of Workington and Whitehaven(Cumbria County Council briefing 05/02).

SECTION III

1. Profile of Allerdale and Copeland Local Authorities

Allerdale CopelandAspatria (2550) Cleator Moor (6760)

Cockermouth (8070) Distington (2280)Keswick (4860) Egremont (7500)

Maryport (11090) Millom (7150) Silloth (3190) Seascale (1770)Wigton (5300)


Allerdale & Copeland

150

TABLE 2 RESIDENT POPULATION BY STUDY AGE BANDS FOR EACH YEAR OF THE STUDY

1996 1997 1998 1999 2000 2001 2002

Age ABC CBC ABC CBC ABC CBC ABC CBC ABC CBC ABC CBC ABC CBC

0-5 6820 5040 6660 4840 6480 4800 6380 4660 6080 4620 5840 4540 5840 4540

6-15 11440 9360 11620 9380 11640 9160 11560 9260 11540 8860 11540 8920 11540 8920

16+ 77440 56200 77820 56380 77980 56140 77660 55880 77280 55720 76220 55540 76220 55540

Sub Total 95700 70600 96100 70600 96100 70100 95600 69800 94900 69200 93600 69000 93600 69000

Area Total 166,300 166,700 166,200 165,400 164,100 162,600 162,600

Local administrationThe present county of Cumbria was createdin 1974 following extensive re-organisation oflocal government. Today Cumbria Countycomprises 6 district council areas, namely:Allerdale, Carlisle, Copeland, Eden,forming the North Cumbria HealthAuthority area until re organised into PrimaryCare Trusts in April of 2002 and Barrow; andSouth Lakeland, which were in MorecambeBay Health Authority. (Hyper-linked textunderlined).

About Allerdale

Allerdale is a district ofimmense variety ranging fromthe fells of the central LakeDistrict to the Solway Plain

and coast. Situated at the western end of thereconstructed A66 scenic route from the M6at Penrith, it also has good links with themain Anglo Scottish road and rail routes atCarlisle. Harbour facilities are available atWorkington and Silloth, handling goods forlocal industry. Allerdale has a wide range ofmanufacturing employment centred onWorkington and Maryport, much of itattracted to the area as result of successiveGovernment’s Regional Policy. Agriculture,particularly cattle, sheep (both lowland andhill farms) and dairy farming form asignificant part of the areas economy. Tourismis a major source of revenue and employment

both within the Lake District National Parkaround Keswick and, increasingly in themarket towns of Wigton Aspatria andCockermouth and Solway coastal areasbetween Maryport and Silloth.

The local authority is working towards theeconomic regeneration of the area through arange of initiatives and strategic partnershipsincluding the comprehensive redevelopmentof Workington Town centre, the proposedacquisition of a disused Royal NavelArmaments Depot for tourism, recreation andhousing uses, market towns initiative andother measures to provide employment,enhance tourism and sustain the ruraleconomy following the Foot & Mouth diseaseoutbreak in 2001.

About Copeland

Copeland is a coastal districtbetween the mountains ofthe Lake District and the

Irish Sea. Most of its towns owe their growthto local industrial development: Whitehaven,a fine Georgian town based on shipping andcoal; Cleator Moor, Millom and Egremont tolocal riches of iron ore, now exhausted.Copeland is reached via the A66 and A595trunk roads through the northern LakeDistrict, or by the road and railway linking tothe mainline railway and M6 motorway toboth north and south.

DefinituonsABC = Allerdale Borough CouncilCBC = Copeland Borough Council

Note 1Year 2002 figures based on 2001

SourceCarlisle & District PCT Dept. of Public HealthMedicine based on ONS data 2002



151

Whitehaven has a small port, which used toserve local industry. This has recently been re-developed as a tourist and leisure facility,which provides a new focus to the town andacts as a catalyst in its regeneration. A majornew tourist attraction, the Beacon, opened in1996 followed by the “Rum Story” in April2000. The Rum Story is part of the £11.5Millennium Tourism Project, which includedthe renovation of the Historic Harbour,upgrading promenades, ‘The Crows Nest’and ‘The Quest’.The coal and iron industries, which oncedominated the economy of Copeland, havebeen replaced by a variety of new industries,primarily chemicals, nuclear reprocessing atSellafield (British Nuclear Fuels is the majoremployer in West Cumbria, providing directlyor indirectly 50% of the jobs in Copeland)and extensive research and support facilities atthe near by West Lakes Science Park. Othersinclude paper packaging, clothing, scientificinstruments etc. and a major new call centre.Whitehaven is the principal service centre forthe district with an attractive pedestrianisedshopping centre and major leisure centre.Agriculture including dairy, cattle and sheepfarming, particularly in the National Park is asignificant component of the local economyand influences the appearance and mostaspects of the rural environment.

Acknowledgement.

The above information on the Allerdale andCopeland local government areas has beenbased on information from Cumbria CountyCouncil.See the County Council home page atwww.cumbria.gov.uk

The following provide links to the districtCouncils’ websites, a short statistical profile ofthe district and local parish, ward & urbanprofiles.www.cumbria.gov.uk/aboutcumbria/allerdale/default.asp

www.cumbria.gov.uk/aboutcumbria/copeland/default.asp



152


2. Water Supply in Allerdale and Copeland1 March 1996 to 31 August 2002

A. Description of water supplyzones, and water treatment works(WTW).

IntroductionA large part of the study area is situatedwithin the Lake District National Park, muchof it upland. Surface water is abstracted froma number of the naturally occurring lakes,stream sources and occasionally rivers, fordrinking and industrial purposes. Many of thenatural lake sources have had their capacityincreased by impounding or damming oftheir outlets to provide adequate storage ofraw water. Groundwater abstraction is limitedto supplementing these sources and supplyingwater treatment works in specific locations orcommunities. More than 166,000 (99%approx.) of the resident population in thestudy area have available a mains or “public”water supply. The statutory water undertakerfor the study area throughout the period ofthe study was North West Water Limited(NWW) until the company changed its namein April 2001 to United Utilities Plc (UU).

The remainder, 1360 (1%) approx. residents,receive water from some 400 “private”sources, principally streams, springs and a fewboreholes for larger volumes of water in moreisolated areas; these rarely serve more thanindividual properties or small groups ofdwellings. Treatment (when provided) forprivate supplies is largely point of use devicessuch as cartridge filters and / or ultra violet(UV) disinfection treatment

Water Supply Zones in Allerdale andCopelandFor water quality monitoring purposes, thesupply and distribution network is dividedinto water supply zones (WSZ), designated by

United Utilities in accordance with theregulatory requirements (see section I). Eachzone is limited to a maximum of 50,000residents, as estimated by the company. Thetreated water for a particular zone can bederived from an individual water treatmentworks (WTW) dedicated to supplying thezone or blending of the outputs from anumber of WTW. In some cases an individualworks output may be sufficient to supplymore than one zone.

The Water Supply (Water Quality)Regulations 1989, Section 29 [2], furtherrequire that a water undertaker prepare andmaintain for each of its WSZ’s, a recordcontaining the name of the zone, the name ofany water treatment works from which wateris supplied to premises within the zone and anestimate of the population of the zone. Thewater undertaker must review and update thisinformation at least once in each year.

At the commencement of the study, the WaterCompany provided a description of the nameand identification number for each WSZ, thename(s) of the WTW supplying each zoneand an estimate of the zone’s population. Tofurther assist the conduct of the study andmaintain patient confidentiality, the companyalso provided a detailed translation sheet toenable the postcode of residence for each caseand its respective controls to be linked to therelevant WSZ, without the need to disclosethe address to the company.

This paper-based method was used until Juneof 1999, when the company supplied aspreadsheet of the WSZ’s and the postcodesassociated with each zone. This enabledsearches to be done electronically and wasincorporated into the administrative database


Water Supply in Allerdale & Copeland - Description

154

used to manage the case and controlinformation, providing automatic selection ofthe WSZ details when the postcode details forthe case or control were entered. Additionally,the company’s Geographical InformationSystem (GIS) was used to provide relevantzone mapping information, WSZ populationestimates and data exports that could be usedby the study to maintain our informationsources on the WSZ’s and postcodes.

Tables 3 and 4 detail the zone numbers andtheir names together with the water treatmentworks serving the zone for the period 1stMarch 1996 to 31st August 2002 for theAllerdale and Copeland local authority areas.

TABLE 3 ALLERDALE WATER SUPPLY ZONE

DESCRIPTIONS

TABLE 4 COPELAND WATER SUPPLY ZONE

DESCRIPTIONS

These methods were essential to themanagement of the case and control data forsubsequent analysis because some of theWSZ’s were not co-terminus with theboundaries of the local authority areasinvolved in the study and in other parts of thestudy area there was no public water supply. Italso enabled the study to cope with certainpostcode areas that were renumbered by thepost office and ensure that these new codestogether with new housing were correctlyallocated to existing WSZ’s. Finally, theannual updating of the records from the watercompanies GIS system also enabled accountto be taken of changes that the company hadmade to any WSZ boundaries for operationalreasons.

Importantly, there were no major changes tothe boundaries of the water supply zonesduring the study period.

For analysis purposes, all cases and controlsrecruited to the study that were not on amains supply were assigned a WSZ code of 0(zero) and named as “Private”

The map at figure 2 shows the areas coveredby the above named WSZ’s and the locationof the main towns and lakes.

Zone Number Zone Name WTW serving zone

4 Quarry Hill CornhowQuarry Hill

5 Fellside Castle CarrockFellside (Note 1)

6 Hayknott Hayknott

7 Longlands Quarry HillLonglands adit

27 Hausegill CornhowHausegill

28 Crummock North Cornhow

29 Crummock South EnnerdaleCornhow

30 Underscar (Keswick) UnderscarBridge End

33 Buttermere Buttermere (Sailbeck)

34 Grange / Grange (Green-Up-Syke)Borrowdale Closed June 1998

Bridge EndFrom June 1998

35 Combe Gill Combe Gill (Note 2) Closed June 1998

37 Thirlspot Thirlspot

Note 1. Although the zone is shown as being supplied by

two WTW, the Fellside WTW alone supplies all drinking

water to premises within the area of WSZ 5 that is within

the Allerdale Borough Council area.

Note 2. Zone 35 was amalgamated with the existing zone

34 on closure of Combe Gill WTW in June of 1998 and

the zone 35 and the name were deleted from the company’s

records.


31 Ennerdale North Ennerdale(Note 1)

32 Ennerdale South Ennerdale

36 Wormgill Coldfell (Wormgill)Closed Nov. 2001

EnnerdaleFrom Nov. 2001

39 Millom LanthwaiteClosed March 2001

UlphaPoaka Beck

Note 1. Zone 31 also covers a number of villages and rural

hamlets within the southwest part of the Allerdale Borough

Council area.


Water Supply in Allerdale & Copeland - Description

155

Water sources and treatment worksA comprehensive review of water source typesand treatment processes is provided in section7 of the “Report of the Group of Experts -Cryptosporidium in Water Supplies” andenlarged upon and updated in Annex 6 of the“Second Report of the Group of Experts -Cryptosporidium in Water Supplies”, bothchaired by Sir John Badenoch [3,4].

At commencement of the study, NWWprovided a public drinking water supply tomore than 99% of the residents of the studyarea. This was achieved by abstracting waterfrom eighteen separate sources (thirteen forthe Allerdale local authority area and five forthe Copeland area). Water from these sourceswas treated in accordance with the relevant,regulatory requirements of the Water IndustryAct 1991[5] at seventeen WTW, (twelve inAllerdale and five in Copeland), beforestorage and distribution to consumersthrough the network of mains, servicereservoirs and supply pipes maintained by thecompany.

The largest of these sources (by volume ofdrinking water produced for residents of thestudy area), Crummock and Ennerdale Lakes,supply water via Cornhow and EnnerdaleWTW, respectively, to approximately 76% ofthe resident population of the study area.

Eleven WTW used surface water from uplandareas held in impounding reservoirs ordirectly from stream sources. Groundwatersourced from two mine adits and two springswas used by five WTW and one WTW useda complex mix of surface water fromimpounding reservoirs and a river, andgroundwater from spring sources augmentedby boreholes.

At commencement of the study, watertreatment other than coarse screening of theraw water and necessary disinfection varied

from no further treatment at a number ofsmaller WTW, micro straining only atEnnerdale and Crummock, to full 3-stagecoagulation aided filtration at other largeworks.

The information on the next page from thewater company summarises the key featuresand processes of each supply and WTW.During the study, continuous microfiltration(CMF) using membrane technology wasinstalled at Ennerdale and Cornhow WTW.Commissioning took place from 1 March2000 to 31 July 2000 after which the CMFplants have been operated continuously.

Importantly, although some small treatmentworks in the study area had closed over theperiod of the study and their suppliestransferred to other supplies, no majorchanges occurred at the other WTW andhence to their water supplies out with thechanges to the Ennerdale and CornhowWTW.


Water Supply in Allerdale & Copeland

156

Summary information from UnitedUtilities on the key features of the watertreatment works used by the watercompany to supply drinking water toresidents of the study area from 1 March1996 to 31 September 2002.

Allerdale

Bridge End WTWBridge End is a small water treatment worksthat abstracts water from the compensationstream leaving Thirlmere impoundingreservoir. Treatment of this soft upland waterconsists of pH correction and disinfection.The WTW supplies a maximum of 4 Ml/d to4000 people in Keswick and the Borrowdalevalley. Identified as “at risk” in accordancewith the 1999 Regulations [6] regardingCryptosporidium in treated waters andcontinuous monitoring installed November2000, with upgrading planned by June 2003.

Buttermere WTW.Buttermere water treatment works abstractswater from Sailbeck, a mountain stream andsupplies an average 0.04 Ml/d (maximum 0.2Ml/d) to 25 domestic properties and 3 hotelsin Buttermere. It is an extremely small WTWwith treatment consisting of slow sandfiltration (coarse filtration) followed bydisinfection. Identified as “at risk” inaccordance with the 1999 Regulationsregarding Cryptosporidium in treated watersand continuous monitoring installed January2001. The works will be upgraded byDecember 2004.

Combe Gill WTW (Closed June 1998)Located at Rosthwaite, Combe Gill WTWtook its raw water from Combe Gill, anupland stream. Treatment at the sitecomprised slow sand filtration (coarsefiltration) followed by disinfection usingsodium hypochlorite.

Cornhow WTWCornhow water treatment works abstractswater from Crummock Water, in Allerdale.The catchment feeding Crummock ismountainous and is underlain by hardimpermeable rock, typically overlain withpeat. The intake to Cornhow WTW is sitedupstream of a canalised section of the ParkBeck main river. This land is designated a siteof special scientific interest by English Natureand the National Trust acts as steward for theland. Under normal operation, CornhowWTW produces between 20-30 Ml/d. Rawwater passes through microstrainers,membrane filtration (accepted into fullservice 17th July 2000) and is then dosed withchlorine gas; phosphoric acid and pHcorrected using sodium hydroxide. Until2001, pH correction was carried out withhydrated lime. Membrane filtration acts as abarrier to the passage of Cryptosporidiumoocysts. The water supply from Cornhow isfluoridated inline with an agreement with theHealth Authority. After treatment, water ispumped to service reservoirs in CrummockNorth and South water supply zones. Thesezones cover a population of 64,000 in Lorton,Workington, Maryport, Broughton Moor,Cockermouth, Silloth and surrounding areas.Identified as “not at risk” in accordance withthe 1999 Regulations regardingCryptosporidium in treated waters whenmembrane filters are operating. Continuousmonitoring implemented if membranefiltration has to be by-passed.

Fellside WTW.The groundwater source for Fellside WTW, aswell as Hayknott WTW, is the Roughton Gillmine adit. The treatment at Fellside consistsof simple disinfection and the averagecapacity of the works is 1.5 Ml/d. FellsideWTW is located within the AllerdaleBorough Council boundary and supplieswater to an approximate population of 2,500.



157

Populations in Rosley, Welton and Seberghamare supplied from Fellside within Allerdale, inaddition to Roughton Head, Gaitsgill,Buckabank, Dalston, Cummersdale, Wreay,Cotehill, Warnhill, Stockdalewath, GreatOrton and Little Orton in Carlisle CityCouncil region. Identified as “ not at risk” inaccordance with the 1999 Regulationsregarding Cryptosporidium in treated waters.

Grange WTW (Closed June 1998)Located at Grange in Borrowdale this small,inaccessible works took its raw water fromGreen-up-Syke which appeared to be a springsupply rather than a stream. Treatment at thesite consisted of slow sand filtration (coarsefiltration) followed by disinfection usingsodium hypochlorite.

Hausegill WTWHausegill is a small WTW, which is situatedin a remote area on steep fells 7 miles north ofKeswick. Hausegill treats water abstractedfrom Hausegill Beck, where the NationalTrust owns the majority of the land. Onaverage the WTW supplies 1.4 Ml/d and isthe sole supply to a population of 2,200 in theBassenthwaite, Bothel, Plumbland and Iselareas. The treatment at Hausegill consists ofroughing filters and simple disinfection.Identified as “at risk” in accordance with the1999 Regulations regarding Cryptosporidiumin treated waters and continuous monitoringinstalled December 2000 and to beabandoned by June 2003.

Hayknott WTWThe groundwater source for Hayknott WTW,as well as Fellside WTW, is the Roughton Gillmine adit. The treatment at Hayknottconsists of simple disinfection and the averageoutput for the works is 0.5 Ml/d. HayknottWTW supplies approximately 750 people inthe villages of Caldbeck, Hesket Newmarket,Branthwaite, Thistlebottom, Brownrigg,

Fellside, Brocklebank, Thornthwaite andThackthwaite. Identified as “ not at risk” inaccordance with the 1999 Regulationsregarding Cryptosporidium in treated waters.

Longlands IntakeThe Longlands Intake is a groundwater sourcereceiving water from the Longlands adit thatis situated in the Borrowdale volcanic rocks.The average output is 0.5 Ml/d and the onlytreatment is simple disinfection. The workssupplies approximately 760 people inTorpenhow, Ireby, Uldale and Whitrigg. Thissource is unreliable, especially during thesummer months and as a consequence thisarea is supported from Quarry Hill WTW.Identified as “ not at risk” in accordance withthe 1999 Regulations regardingCryptosporidium in treated waters.

Quarry Hill WTWThe raw water for Quarry Hill WTW, nearMealsgate, is abstracted from OverwaterImpounding reservoir, Dash Beck and theRiver Ellen via Chapel House ImpoundingReservoir together with Aughertree Springs.Quarry Hill is a three-stage water treatmentworks, which consists of coagulation,dissolved air filtration (DAF), rapid gravityfiltration (RGF), oxidation, second stagefiltration and disinfection. Quarry HillWTW is supplemented when necessary withwater from Scales boreholes, which is subjectto disinfection only. Quarry Hill WTW has atotal supply of 12 Ml/d. The main areassupplied stretches between Bowness onSolway in the North and Mealsgate in theSouth. The supply area includes Wigton,Aspatria, West Curthwaite and Thursby.Identified as “ not at risk” in accordance withthe 1999 Regulations regardingCryptosporidium in treated waters.



158

Thirlspot WTW.Thirlspot water treatment works is situatedadjacent to Bridge End WTW and also treatswater from the compensation stream leavingThirlmere impounding reservoir. ThirlspotWTW consists of disinfection and pHcorrection and has an average output of 0.1Ml/d. Thirlspot WTW supplies water toapproximately 70 people in Thirlspot andCastle Rock. Identified as “at risk” inaccordance with the 1999 Regulationsregarding Cryptosporidium in treated waters.The supply is continuously monitored atBridge End WTW and will be upgraded byJune 2003 with extra filtration stages as thesame source as Bridge End.

Underscar WTW.The source water for Underscar WTW isabstracted from three streams on the fellsnorth of Keswick - Millbeck, The High andRoughten Gill. Treatment consists ofsettlement, disinfection and pH correctionand has a capacity of 4.5 Ml/d. Thetreatment works supplies an approximatepopulation of 7,100 in Keswick, Millbeck,Braithwaite and Thornthwaite. Identified as“at risk” in accordance with the 1999Regulations regarding Cryptosporidium intreated waters. Continuous monitoring wasinstalled in March 2001 and plans to beabandoned by June 2003.

Copeland

Coldfell WTW(Closed November 2001)Coldfell WTW, located 4 km east ofEgremont treated water abstracted from astream source known as Wormgill. Theprocess at the works consisted of coarsestraining, chlorination, phosphate dosing andpH correction. The works output averaged1.7 Ml/d and supplied a population of over2000 in Haile, Calder Bridge, Gosforth,Nether Wasdale and surrounding villages.

Coldfell WTW closed in late 2001 and wateris now supplied to these areas from EnnerdaleWTW. Identified as “at risk” in accordancewith the Regulations regardingCryptosporidium in treated waters.Continuous monitoring installed May 2001but now closed.

Ennerdale WTWEnnerdale WTW treats water abstracted fromEnnerdale impounding reservoir. Treatmentat Ennerdale consists of coarse microstrainers,membrane filtration (accepted into fullservice beginning of April 2000), pHcorrection, disinfection, phosphate dosingand fluoridation. Fluoride is added to thewater in line with an historic agreement withthe Health Authority. Ennerdale WTW hasan average output of 40-45 Ml/d and supplieswater to over 65,000 people in Whitehaven,parts of Workington, Cleator Moor,Egremont, Nether town, Seascale and Bootle.Identified as “not at risk” in accordance withthe 1999 Regulations regardingCryptosporidium in treated waters whenmembrane filters are operating. Continuousmonitoring implemented if membranefiltration has to be by-passed.

Poaka Beck WTWPoaka Beck WTW is situated 1 km north ofMarton Village and receives water from threesources, Pennington stream, Poaka Beck andHarloch Impounding reservoir. Poaka Beck isa three stage WTW with coagulation,dissolved air filtration and rapid gravityfiltration followed by disinfection. Theaverage output from the works is 18 Ml/d andsupplies water to zone 39, which has apopulation of 8,878. The remainder of theoutput from Poaka Beck WTW feeds into theBarrow network and supplies Barrow inFurness and surrounding areas outside theCopeland Borough Council boundary. PoakaBeck WTW alone can supply zone 39 or incombination with Ulpha WTW, this is



159

dependent on the raw water quality at UlphaWTW. Water supply zone 39 covers Millom,The Green and Silecroft. Identified as “not atrisk” in accordance with the 1999 Regulationsregarding Cryptosporidium in treated waters.

Ulpha WTWUlpha WTW abstracts water from the RiverDuddon that in turn is supplied fromSeathwaite impounding reservoir. UlphaWTW supplies up to 10% of total demand inzone 39, including Ulpha village, with surpluswater entering the Barrow network.Treatment at Ulpha includes polymercoagulation with first stage, rapid gravityfiltration, disinfection and second stagefiltration. The maximum supply is 22 Ml/d.Identified as “at risk” in accordance with the1999 Regulations regarding Cryptosporidiumin treated waters. Continuous monitoringinstalled September 2000 and upgrading byadditional clarification and backwash watertreatment by March 2004.

Lanthwaite WTW (Closed March 2001)Lanthwaite WTW abstracted water fromBaystone Bank Impounding reservoir and wasused intermittently to supplement supplies inMillom (zone 39). Treatment at the siteconsisted of pressure filtration followed bypH correction and disinfection. The workswas identified as “at risk” in accordance withthe 1999 Regulations regardingCryptosporidium in treated waters and wastherefore, closed down in March 2001.

Table 5 summarises the arrangement of watersources, WTW and treatment processes foreach of the WSZ in the Allerdale andCopeland local authority areas throughoutthe period of the study.

Distribution & SupplyOnce water has been produced at a watertreatment works, it is distributed through acomplex supply network of gravity fed and

pumped water mains either directly to theconsumer or via storage in service reservoirs.Further disinfection may also be undertakenat “booster” stations to maintain disinfectantlevels throughout the distribution network.



160



161

Tab

le 5

Wate

r S

up

ply

Zon

e an

d s

ou

rce

det

ail

s, t

reatm

ent

work

s d

escr

ipti

on

s an

d p

roce

ss d

etail

s M

arc

h 1

996 t

o A

ugu

st 2

002

Zone

No

Local

Auth

ori

tyZ

one N

am

eP

opula

tion 2001

(or

on c

losure

)

Sourc

eT

ype

%

Supply

Pri

mary

work

sC

oagula

tion

Flo

ccula

tion/

Flo

tati

on

pH

corr

ecti

on

Dis

infe

cti

on

Flu

ori

de

Cru

mm

ock W

ate

rU

WIR

13

Corn

how

+ +

MS

MF

(2)

1C

Y

Quarr

y H

ill

UW

IR, S

T, S

P &

BH

87

Quarr

y H

ill

F

D

RG

F(1

)R

GF

(2)

2A

+

Castl

e C

arr

ock

R &

SP

10

Castl

e C

arr

ock

F

D

RG

F(1

)R

GF

(2)

2N

+

Fell

sid

eA

D90

Fell

sid

e +

+ +

N

+6

Hayknott

749

Hayknott

AD

100

Hayknott

+ +

+N

+

Quarr

y H

ill

BH

,ST

& U

WIR

45

Quarr

y H

ill

F

D

RG

F(1

)R

GF

(2)

2A

+

Longla

nds a

dit

AD

55

Longla

nds

+ +

+N

+

Cru

mm

ock W

ate

rU

WIR

26

Corn

how

+ +

MS

MF

(2)

1C

Y

Hausegil

lS

T74

Hausegil

l +

+C

FS

SF

+N

+

28

Cru

mm

ock N

35015

Cru

mm

ock W

ate

rU

WIR

100

Corn

how

+ +

MS

MF

(2)

1C

Y

Ennerd

ale

UW

IR21

Ennerd

ale

+ +

MS

MF

(1)

2C

Y

Cru

mm

ock W

ate

rU

WIR

79

Corn

how

+ +

MS

MF

(2)

1C

Y

Unders

car

ST

(x3)

78

Unders

car

+S

ET

2C

+

Thir

lmere

CR

22

Bri

dge E

nd

+ +

2N

+

33

Butt

erm

ere

43

Butt

erm

ere

(S

ail

beck)

ST

100

Butt

erm

ere

+ +

+N

+

Gra

nge (

Gre

en-U

p-S

yke)

SP

(C

lose

d J

un

e 1998)

0G

reen U

p S

yke

+ +

+N

+

Thir

lmere

CR

100

Bri

dge E

nd

+ +

2N

+

Com

beG

ill

ST

(C

lose

d J

un

e 1998)

0C

om

be G

ill

+ +

+N

+

Thir

lmere

CR

100

Bri

dge E

nd

+ +

2N

+

37

Thir

lspot

125

Thir

lmere

CR

100

Thir

lspot

+ +

2N

+

Tota

l P

op

.91907

31

Ennerd

ale

N44370

Ennerd

ale

UW

IR100

Ennerd

ale

+ +

MS

MF

(1)

2C

Y

32

Ennerd

ale

S19000

Ennerd

ale

UW

IR100

Ennerd

ale

+ +

MS

MF

(1)

2C

Y

Cold

fell

(W

orm

gil

l)S

T (

Clo

sed

Nov./

Dec

2001)

0C

old

fell

+ +

2N

+

Ennerd

ale

UW

IR100

Ennerd

ale

+ +

MS

MF

(1)

2C

Y

Lanth

wait

e(C

lose

d M

arc

h 2

001)

(5)

Lanth

wait

eP

+ +

N

+

8700

Ulp

ha

R10

Ulp

ha

P -

RG

F(1

)R

GF

(2)

2O

+

Poaka B

eck

ST

(x2),

UW

IR85

Poaka B

eck

FD

RG

F(1

)R

GF

(2)

2N

+

Tota

l P

op

.74889

F=

Ferr

ic s

ulp

hate

1 =

Lim

e

P=

Poly

mer

aid

ed

2 =

Sodiu

m H

ydro

xid

e

Flo

ccu

lati

on

/ F

lota

tion

D=

Dis

solv

ed a

ir f

lota

tion w

ith R

GF

(2)

aft

er

flota

tion p

rocess

A =

Am

monia

tion

CF

= C

oars

e f

iltr

ati

on

(

Sodiu

m H

ypochlo

rite

&

BH

MF

(1)

= M

em

bra

ne f

iltr

ati

on f

rom

1/4

/2000

A

mm

oniu

m n

itra

te)

R =

Riv

er

MF

(2)

= M

em

bra

ne f

iltr

ati

on f

rom

1/8

/2000

C =

Chlo

rine g

as

SP

=

Spri

ng

MS

= M

icro

str

ain

ers

N =

Sodiu

m H

ypochlo

rite

Pre

ssu

re=

Fil

trati

on u

sin

g n

atu

ral

head o

f w

ate

r

ST

=

Str

eam

RG

F(1

)= R

apid

gra

vit

y f

ilte

r sta

ge 1

RG

F(2

)= R

apid

gra

vit

y f

ilte

r sta

ge 2

Y =

Pro

cess a

vail

able

SE

T=

Sett

lem

ent

tank

Y =

Pro

cess a

vail

able

SS

F=

Slo

w s

and f

ilte

r +

=It

em

not

pre

sent

at

work

s

UW

IR =

Upla

nd w

ate

r, i

mpoundin

g r

eserv

oir

CR

Flu

ori

dati

on

Ph

osp

hate

dosi

ng

Fil

trati

on

=

Bore

hole

All

ite

ms

=

Com

pensati

on r

ele

ase f

rom

im

poundin

g r

eserv

oir

Coagu

lati

on

ph

Corr

ecti

on

Dis

infe

ctio

n

Sou

rce

typ

e

AD

= G

round w

ate

r fr

om

min

e a

dit

KE

Y

Cop

elan

d

(400)

35

Com

be G

ill

39

Mil

lom

A l l e r d a l e

Gra

nge /

Borr

ow

dale

27

Hausegil

l

29

Cru

mm

ock S

30

Unders

car

(Kesw

ick)

6160

CF

All

erd

ale

pre

ssu

re

CF

CF

& S

SF

CF

1343

CF

& S

SF

34

36

Worm

gil

l2819

CF

C o p e l a n d

7L

ongla

nds

626

CF

4Q

uarr

y H

ill

16258

CF

5F

ell

sid

e

O =

OS

EC

(on s

ite

ele

ctr

oly

tic c

hlo

rinati

on)

Tre

atm

ent

2251

Fil

trati

on

1226

CF

CF

28111

CF

CF

Phosp

hat

e

dosi

ng

Y

+ Y + + + + Y + Y Y Y + + + + + + + + Y Y Y Y + + +

TA

BL

E 5

W

AT

ER

SU

PP

LY

ZO

NE

AN

D S

OU

RC

E D

ET

AIL

S, T

RT

EA

TM

EN

TW

OR

KS

DE

SCR

IPT

ION

AN

D P

RO

CE

SS D

ET

AIL

S M

AR

CH

199

6 T

O A

UG

UST

2002


Water Supply in Allerdale & Copeland - District Meter Areas

162

B. Description of District MeterArea (DMA), changes in watersupply arrangements and estimationof WSZ Populations

District Meter Areas To assist in the management of their WSZ’s,distribution networks and the reconciliationof water produced against the volumeconsumed and that lost due to leakage, thewater industry has developed the concept ofsub dividing their WSZ’s into a number ofDistrict Meter Areas (DMAs).

Each DMA represents a discrete part of thedistribution network within a WSZ, withmetering of the volume of water supplied intoit. A DMA usually supplies up to 3000properties and is controlled by dedicatedisolation valves to separate it from the rest ofthe supply network Adjustments to theconfiguration of these valves and theinstallation of additional meters, allows forthe number of DMA’s in a WSZ to beadjusted.

At a meeting regarding DMA’s, the watercompany explained that detailed records oneach DMA are kept as part of the company’scontrol systems. These records includepopulation estimates, the volume of watersupplied, primary water sources and WTWfor each DMA and any major works,engineering operations or changes to thenumber of DMA’s.

The DMA’s are recorded as part of thecompany’s Geographical Information System(GIS) and data exported from this has beenprovided to the study to enable any postcodein the study to be linked to its respectiveDMA. The company confirmed that theDMA’s in the study area had been subject toonly a few, well-documented alterations andadditions, apart from some very short termengineering changes. To assist the study, the

company supplied detailed schematic andmap based information of their water maindistribution network and DMA’s togetherwith a detailed explanation of the alterationsthat had been made. The short-term changeswere necessary to ensure the continuity ofsupply to a DMA during planned work,engineering trials or in response to a burst;and could involve supplying the DMA from adifferent WTW and water source. Due to theshort duration of these events, records werenot easily available; however these events wereconsidered unlikely by the company to haveinfluenced major or significant changes in thewater sources for the affected DMA.

Nevertheless, the DMA information that hasbeen made available provides a robust methodof determining the water source andtreatment works for any given postcode ofresidence for a case or control recruited to thestudy.

ChangesDiscussions were held with company repre-sentatives to identify and resolve any issuesregarding changes to WSZ’s and theirboundaries or populations, or to the watertreatment arrangements.

During the course of the study, four small-scale WTW were closed by the company foroperational reasons and water supplied fromother existing works in the study area. Table 6details the WSZ’s that were affected, the datesof the closures and the alternative WTW usedto maintain the supply to the zone.

The discussions confirmed that there hadbeen no major changes to the WSZboundaries and hence varying exposure to thewater sources in the study area. In particular,the boundary between WSZ 28 CrummockNorth, (DMA 28-03 up to Silloth) and WSZ4 Quarry Hill, (DMA 04-01 Aspatria area)had not changed


Water Supply in Allerdale & Copeland - District Meter Areas

163

Mixed SupplyHowever, the company’s information onDMAs showed there were a number ofdiscrete areas associated with particularDMA’s, and hence any residents within them,that had received water from the main WTWassociated with the Crummock andEnnerdale sources as well as water treated atanother WTW from a different source. For

the purposes of analysis, this method ofsupply was considered to have created adifferent exposure to the water source andtreatment for cases and controls occurring inthe affected DMA’s. Accordingly, using theinformation provided by the company, thecases and controls recruited to the study thatwere affected by this situation had their WSZcategorised as “mixed” and coded 99. Thisenabled them to be analysed as a distinctcategory of mixed water supply in theanalysis. The definition of “mixed” watersupply DMA was only used for those DMA’sthat received mixed water from Crummockand Ennerdale water sources, or Crummockor Ennerdale and another source.

In addition to these changes, the discussionsalso identified that WSZ 7 (Longlands),serving approximately 760 people inTorpenhow, Ireby, Uldale and Whitrigg, andWSZ 30 (Underscar) serving an approximatepopulation of 7,100 in Keswick, Millbeck,Braithwaite and Thornthwaite weresupported by mixing the supply with watertreated at Quarry Hill WTW and Bridge End,respectively. However, these supplies did notinvolve Crummock or Ennerdale sources andtherefore were not included in the previousdefinition of “mixed” water supply.

TABLE 6 WTW CLOSURES AND

ZONES AFFECTED


34 Grange/ Grange (Green-Up-Syke)

Borrowdale Closed June 1998


35 Combe Gill Combe Gill (Note 1) Closed June 1998


36 Wormgill Coldfell (Wormgill)

Closed Nov. 2001

EnnerdaleFrom Nov. 2001

39 Millom LanthwaiteClosed Mar. 2001

Ulpha

Poaka Beck

Note 1. Zone 35 was amalgamated with the existing zone 34

on closure of Combe Gill WTW in June of 1998 and the

zone 35 and the name were deleted from the company’s

records.

Zone Number Zone Name WTW serving zone Main WTW Blending WTW Areas affected

28 Crummock North 028-21 & 028-22 Cornhow Hausegill Tallentire & Bridekirk,

nr Cockermouth

29 Crummock South 029-01 Cornhow Ennerdale High Harrington, Workington

31 Ennerdale North 031-10 & 031-21 Ennerdale Cornhow Lowca & Low Moresby,

Whitehaven and Salterbeck,

Workington

32 Ennerdale South Thornhill area Ennerdale Wormgill Thornhill Estate, Egremont.

36 Wormgill All DMA�s in WSZ Wormgill Ennerdale Gosforth & Haile area

TABLE 7 WSZ NUMBER, NAMES AND DETAILS OF �MIXED� DMA�S



164



165

Figure 3 shows the location of the DMAs andWSZ’s affected by “mixing” in the Allerdaleand Copeland local authority areas,respectively.

Water Supply Zone Population EstimatesNWW has provided for each year of the studyestimates of the resident population served bymains drinking water in each of the WSZ inthe study area described in section III part A,above. The company also provided estimatesof the populations affected by the “mixing” ofwater from Crummock and Ennerdale watersources, or Crummock or Ennerdale andanother source described in table 7 (above).

In addition to the estimation of the residentpopulation receiving mains drinking water, itwas also necessary to estimate the number ofresidents receiving water from a “private”water supply. This was achieved by obtainingthe number of domestic residences with aprivate water supply recorded in the publicregister of information maintained by both ofthe study area local authorities, in accordancewith the Private Water Supply Regulations1991. These were then converted to numberof residents by multiplying by the averagehousehold size for each local authority (basedon 1994 estimates using 1991 census data).

The denominator populations used in thestatistical analysis undertaken by CDSC werecalculated by amalgamating the populationsof the WSZ receiving water from Crummocklake source to produce the Crummockdenominator population; and amalgamatingthe populations of the WSZ receiving waterfrom Ennerdale lake source to produce theEnnerdale denominator population. From thepopulations receiving water from Crummockand Ennerdale sources were deducted thenumber of residents of the DMA’s describedin table 7 as having a “mixed” supplyassociated with a Crummock or Ennerdalesource WSZ.



166

TABLE 8 ANALYSIS OF UNITED UTILITIES WSZ POPULATION FIGURES, CALCULATION OFPRIVATE AND MIXED SUPPLY POPULATIONS AND TOTAL POPULATION.

1996 1997 1998 1999 (A) 2000 (B) 2001 2002 (B)

Allerdale 28 & 29 Crummock 57120 57120 57120 61820 61820 60220 60220Copeland 31 & 32 Ennerdale 47480 47480 47480 48680 48680 50880 50880

Sub Total (1) 104600 104600 104600 110500 110500 111100 111100

4 Quarry Hill 19000 19000 19000 16600 16600 16300 163005 Fellside 3000 3000 3000 2400 2400 2250 22506 Hayknott 700 700 700 740 740 750 7507 Longlands 500 500 500 680 680 600 60027 Hausegill 2200 2200 2200 1500 1500 1200 120030 Underscar (Keswick) 7100 7100 7100 6300 6300 6160 616033 Buttermere 200 200 200 37 37 43 4334 Grange/Borrowdale 300 300 300 1500 1500 1340 134035 Combe Gill 400 400 40037 Thirlspot 50 50 50 80 80 125 1250 Private Supplies (Note C) 650 650 650 650 650 650 65099 Mixed supplies (Note D) 2880 2880 2880 2880 2880 2880 2880

Sub Total (2) 36980 36980 36980 33367 33367 32298 32298

Copeland(other) 39 Millom 7000 7000 7000 9350 9350 8700 8700

0 Private Supplies (Note C) 715 715 715 715 715 715 71599 Mixed supplies (Note D) 15320 15320 15320 15320 15320 15320 15320

Sub Total (3) 23035 23035 23035 25385 25385 24735 24735Population Grand total

(Sub totals 1,2 & 3) 164615 164615 164615 169252 169252 168133 168133

A = Revised estimation method introduced by United Utilities for WSZ population.B = Figures for these columns use previous years populations

WSZ No. DMA No. Population of DMA WSZ No.DMA No.28-21 160 31-1028-22 550 31-21

29 29-01 2170 32 32-15 3420

Coded 99 (MixedSupplies) Total

15320

36All

DMA's2800

Coded 99 (MixedSupplies) Total

2880

Incorporated into WSZ 34

LocalAuthority

WSZ No. Zone NameYear

C = Population estimated from number of homes on private supplies from Local Authority register multiplied by 1994average household size for each local authority (Cumbria County Council facts & figures for each Local AuthorityD = Mixed supplies population calculated as shown in each table (below) and each mixed DMA population deductedfrom its respective WSZ population

Allerdale(other)

N.B.

Allerdale CopelandPopulation of DMA

28 3148204280

All other WSZ populations, plus the populations of the mixed DMA’s defined above and thepopulation estimated to receive drinking water from a private supply were amalgamated to formthe category “Other” water.

The above details have then been summarised in Table 9 into the yearly denominator populationfor the sources of 1) Crummock, 2) Ennerdale and 3) “Other over the course of the study.



167

1996 1997 1998 1999 2000 2001 2002

1 57120 57120 57120 61820 61820 60220 60220

2 47480 47480 47480 48680 48680 50880 50880

3 60015 60015 60015 58752 58752 57033 57033

T otal 164615 164615 164615 169252 169252 168133 168133

B reakdow n of "other" above

1996 1997 1998 1999 2000 2001 2002

(N ote 4) 40450 40450 40450 39187 39187 37468 37468

99 18200 18200 18200 18200 18200 18200 18200

0 1365 1365 1365 1365 1365 1365 1365

T otal 60015 60015 60015 58752 58752 57033 57033

Y ear

M ixed

P rivate

O ther public

O ther

W ater SourceY ear

Crum m ock

E nnerdale

W ater Source

TABLE 9 STUDY DENOMINATOR POPULATION ESTIMATES 1996 TO 2002

N.B.1). Crummock produced by the amalgamation of W S Z�s 28 & 29 populations, less D M A population with

mixed supply.2). Ennerdale produced by the amalgamation of W S Z�s 31 & 32 populations, less D M A population with

mixed supply3). Other produced by the amalgamation of the yearly population of W S Z�s 4,5,6,7,27,30,33,34,35,& 37

(Allerdale), 39 (Copeland) plus all mixed D M A populations and private supply populations for Allerdale & Copeland.

4). Other Public produced by the amalgamation of the yearly populations of W S Z�s 4,5,6,7,27,30,33,34,35,& 37 (Allerdale) and 39 (copeland)

Source.United Utilities Annual Report to Local Authorities (for W S Z�s population estimates)Data from United Utilities on D M A population and mixing of Water Sources

C. Description of Membrane filters(A summary from informationprovided by United Utilities Water Plc).

Continuous microfiltration (CMF)membrane technology was chosen by NWW(Predecessor company to UU) for Ennerdale& Cornhow WTW.

Process selectionThe company reviewed the availabletechnologies and their ability to removeCryptosporidium spp. [7] This identified thatdirect filtration or Fibre/Thread filtrationrelied on a number of filtration mechanismsand required a certain concentration ofparticles for them to work effectively. Theselimitations raised questions for the companyabout the ability of these methods to providea robust & reliable barrier to Cryptosporidium.

Conversely, both Membrane microfiltration(MF), typical pore size 0.1µm or greater andUltra Filtration (UF), typical pore size0.01µm, would represent a purely physicalbarrier, based on the exclusion of particlesgreater than the pore size of the selectedmembrane. In North West Waters view, thisarrangement represented a more robustprocess and, provided the integrity of thesystem including the membrane wasmaintained and monitored, a reliable barrierwould be achieved.

Pilot plant trials found that coliforms,turbidity and algae were removed to thedetection limits of the analytical technique; inaddition a small fraction of colour wasremoved. Particle counting was carried outand removal was found to be at the noise levelof the instrument in the 2-5µm particle size.

After pilot plant trials at Ennerdale WTW,the company was recommended to adopt USFilter (part of the Vivendi group) Memcor(r)continuous membrane filtration (CMF) forboth Ennerdale and Cornhow WTW [7] Thespecification included a requirement that themembrane remove to 99.99% (Log 4)efficiency, particles in the 2-5µm range.

Full scale plantThe filters are formed from polypropylenehollow fibres, with a nominal pore size of0.2µm.

Many hundreds of these are packed andformed into a sub module, with proprietaryend terminations for insertion into a filtercolumn; and with the necessary “O” ring sealsand connectors to the pipe-work and valves ofa filter module.

Fig. 4 Filter sub module with fibres exposed


Water Supply in Allerdale & Copeland - Membrane Filters

168



169

Each module has an equivalent surface area of15m.

90 modules are grouped to form a filter unit,mounted on a purpose-designed rack called a“Skid”

The skid is provided with valves, controls &wiring to permit modular construction andminimize field piping and wiring to connectthe units to the mechanical & electrical plant,equipment and control systems of the WTW.A total of 19 skids are present at Ennerdaleand 10 skids at Cornhow

Filtration process

The number of filters skids in use is dictatedby the need to keep a set water level in thechlorine contact tank, to keep pace withdemand.

After coarse screening (500 µm particle size),raw water is fed via variable speed pumps toeach filter skid at a constant head of between22-24 metres.

Fig. 5 Assembled filter modules atEnnerdale

Fig. 6 Schematic of the CMF process at each WTW

Fig. 7 Micro strainer at Cornhow WTW

Fig. 8 CMF “Skids” at Cornhow WTW

2



170

As filtration proceeds a “fouling” layer buildsup on the surface of the membrane, increasingthe pressure that is necessary to drive wateracross the membrane (Trans membranepressure, TMP). TMP must be controlled sothat the required volume of water can beproduced. Control is achieved by periodically“backwashing” the filter modules in aparticular unit, using an automated processthat takes between 1.5 to 3 minutes, either ona pre determined cycle or at a set TMP.

Backwashing consists of draining down thefilter modules and using low-pressure air todrive all water out of the clean side. Onceachieved, air pressure is increased to 90psi andreleased to the raw water (feed) side, throughthe membrane; resulting in a surge of air, dirt& water being released from the module to adedicated tank.

A high velocity, raw water flush is then used,in combination with a short period of airbeing pushed through from the clean side.The resultant air and water scour sweepsacross the membrane surface removing thebuild up of solids in the feed side. At the endof the above cycle, the unit is put back infiltration mode to fill both the feed and cleansides. Air pressure is used to increase systemwater pressure and then released from theclean side to drive any residual air from themembrane pores.

Chemical in Place Cleaning (CIP)Backwashing alone cannot prevent an increasein TMP over time due to fouling that canonly be removed by CIP. Polypropylenemembranes are claimed by the manufacturerto be resistant to pH and, due to the depth ofthe membrane, can be cleaned frequentlywithout shortening its life. Caustic soda(Sodium hydroxide) 2% solution, Sulphuricacid solution 2% and Hydrogen Peroxidewith proprietary surfactants (Memclean®) are

used at Ennerdale & Cornhow on monthly,bi-monthly and annual cleaning cycles,respectively, for each cleaning solution.

The process is fully automated apart fromoperator involvement in instructing thesystem to prepare for a CIP, isolating the unitfrom the rest of the system and initiating theclean process.

The program includes both circulation andsoaking periods and is completed inapproximately 2 hours. On completion, low-pressure compressed air is used to empty theunit of cleaning solution to a storage tank forre-use. Two backwash sequences (as describedabove) and a rinse procedure are conducted. Aconductivity meter, to confirm theelimination of chemical residues, monitorsthe effectiveness of the rinse down.

Membrane Integrity MonitoringThe Drinking Water Inspectorate hasapproved a number of membranes andmembrane systems following an assessmentperformed by the Laboratory of theGovernment Chemist as to their capability ofcontinuously removing or retaining particlesgreater than one-micron diameter. Meetingthis criterion is considered sufficient andappropriate for Cryptosporidium removal, asoocysts are typically 4-6 µm in diameter. TheKoch Membrane Systems membranes, whichhave been provided at both Ennerdale andCornhow, are approved under this scheme.

Generally, membrane elements are housed ina vessel enclosed at each end with end caps -this is defined as a module. Individualmembrane modules need to be individuallytested regularly for integrity so that any fault(e.g. fibre break, fibre degradation, o-ringfailure etc.) can be identified and the faultrepaired. This type of non-destructive test isknown as a Membrane Integrity Test (MIT).



171

Commercial membrane modules haverelatively low treatment capacity. Thus atypical membrane treatment plant isconstructed of many modules built into skids,arrays and treatment trains. A very large plantcan have hundreds, even thousands ofmembrane modules. Ennerdale has 1,530modules; Cornhow has 900.

As these modules are grouped into skids, it ispractical to first perform a MIT of a skid. Ifthe skid passes then the individual membranemodules must be integral. If it fails, eachmodule must be checked to identify the faultso that it can be repaired.

A membrane process train is a series ofmodules and processes, which make up acomplete treatment process. A membranebased water treatment works may have severalparallel process trains, which can be operatedindependently if required. It is possible tocheck a treatment train or the whole plant forintegrity as a first course of action. If thewhole plant fails an integrity test, then eachsection of the plant will have to be tested untilthe faulty module(s) is/are identified andrectified.

The MIT used at Cornhow and Ennerdale isa Pressure Decay Test (PDT) and isperformed weekly. This test involves applyingpressurised air at the feed side to apredetermined pressure below the bubblepoint and then isolating. When the pores ofa membrane are filled with liquid and airpressure is applied to one side of themembrane, surface tension prevents the liquidin the pores from being blown out by airpressure below a minimum pressure known asthe bubble point. The predeterminedpressure directly relates to the size of defectunder investigation. At Ennerdale andCornhow the test pressure is 100 kPa, whichcorresponds to a theoretical defect size of 0.6to 0.8 µm.

The air pressure is monitored for a period oftime (2 to 10 minutes) to observe the rate ofdecay. A small decrease of up to 1.5 kPa perminute is considered acceptable and is due tothe diffusion of air across the microporousmembrane structure. A faster decrease inpressure indicates a faulty membrane. As themembrane system is open to atmosphericpressure on the filtrate side, the airflow can beobserved to confirm the location of anybreach. Suspect modules can be isolated untilsuch time as they are replaced. The method iscapable of detecting changes in integrity up toabout 4.5 - 5 LRV (log removal value). LRVsare calculated based on system size and forplants containing a relatively small number ofmodules, the detection of a single fibre breakconstitutes a calculated LRV of less than 4.Larger plants containing a greater number ofmodules will have a calculated LRV in excessof 4 but less than 5.

In conjunction with the DWI, UU haveconducted an audit of their membraneintegrity testing procedures including thefrequency of pressure testing. The DWI hasissued guidance to all water companies onCryptosporidium in water supplies andmembrane integrity monitoring. [8]



172

D. Dates of membrane filterscommissioning - Informationprovided by UU

Ennerdale WTWFlow first went into supply on the afternoonof the 29 February 2000 and the flow fromthe CMF plant was continuous from 23March 2000.The plant has been operated several timessuccessfully, using the on site generatorcapacity during mains supply “outages”.

Cornhow WTWFlow first went into supply for several hourson the 27 April 2000. Flow continued intosupply but only for extended daytimeworking, with full attendance by North WestWater staff whilst initial problems wereaddressed. Continuous operation modestarted on the 17 July 2000.

Most minor problems have been resolvedwithout the need to go to by-pass (of theCMF plant). There have been two occasionsof need to go to by-pass, one for a period oftwo hours whilst a problem was investigatedand resolved and one to allow plannedmodifications to the power supply andcontrol arrangements to take place.

There is currently only around 15 to 20minutes of treated water storage at Cornhowand if the membranes should blind it wouldbecome necessary to by-pass them. TheCompany is developing a managementstrategy that would allow for such exceptionalcircumstances in order to maintain supplies tothe distribution system. This provision is atemporary arrangement pending completionof a capital scheme to provide a large servicereservoir for Cornhow within the next twoyears. Additional reconfiguration of storagewithin the distribution system will then allowup to 24 hours storage.

MonitoringThe well-established collection of raw watersamples for analysis for Cryptosporidium andGiardia has continued at both sites, and inaddition rigs have been provided to permitcontinuous monitoring in the event of theneed to initiate the by-pass procedures.


Water Supply in Allerdale & Copeland - Monitoring Cryptosporidium

173

E. Monitoring of Cryptosporidiumin Ennerdale and CornhowWTW

Since midyear of 1995, the water companyhas undertaken a programme of monitoringthe raw water entering Cornhow andEnnerdale WTWs for both Cryptosporidiumspecies oocysts and Giardia cysts. Samples are

taken as 10 litre “grab” or “spot” samples froma dedicated sampling point on the raw waterinlet to each works. The samples are thentransported to United Utilities laboratory atWarrington for analysis.

Results of the monitoring are tabulated foreach year on the following pages andsummarised below (Table 10, 11).

1996 1997 1998 1999 2000 2001 2002 Total

Number ofsamples (n)

60 91 99 103 128 100 62 643

Numberpositive (%)

1 (1.6%) 10 (11.0%) 0 9 (8.7%) 21 (16.4%) 17 (17%) 8 (12.9%) 66 (10.3%)

Min(Oocysts /

Litre)0 0 0 0 0 0 0 0

Max(Oocysts /

Litre)0.2 0.4 0 0.3 0.6 2 0.3 2

Table 10 Summary raw water monitoring (10 litre "grab" samples) at Cornhow WTW

Cryptosporidium monitoring results for Cornhow WTW 1 January 1996 to 31 July 2002

1996 1997 1998 1999 2000 2001 2002 Total

Number ofsamples (n)

51 88 103 95 101 99 61 598

Numberpositive

(%) 12 (23.5%) 14 (15.9%) 21 (20.4%) 13 (13.7%) 19 (18.8%) 21 (21.2%) 11 (18.0%) 111 (18.6%)

Min(Oocysts /

Litre)0 0 0 0 0 0 0 0

Max(Oocysts /

Litre)0.3 1.7 1 0.7 0.6 1 0.3 1.7

Cryptosporidium monitoring results for Ennerdale WTW 1 January 1996 to 31 July 2002

Table 11 Summary raw water monitoring (10 litre "grab" samples) at Ennerdale WTW

TABLE 10 SUMMARY RAW WATER MONITORING (10 LITRE �GRAB� SAMPLES) ATCORNHOW WTW

TABLE 11 SUMMARY RAW WATER MONITORING (10 LITRE �GRAB� SAMPLES) ATENNERDALE WTW


Water Supply in Allerdale & Copeland - Monitoring Cryptosporidium - Cornhow

174

Cornhow - Raw water

Date Cryptosporidium/L Giardia/L

1996

30-Jan 0 0

02-Feb 0 0

05-Feb 0 0

12-Feb 0 0

13-Feb 0 0

19-Feb 0 0

20-Feb 0 0

26-Feb 0 0.1

29-Feb 0 0

08-Mar 0 0

13-Mar 0 0

14-Mar 0 0

15-Mar 0 0

18-Mar 0 0

21-Mar 0 0

29-Mar 0 0

01-Apr 0 0

03-Apr 0 0

04-Apr 0 0

09-Apr 0 0

10-Apr 0 0

15-Apr 0 0

30-Apr 0 0

07-May 0 0

08-May 0 0

09-May 0 0

16-Jul 0 0

22-Jul 0 0

25-Jul 0 0

29-Jul 0.2 0

30-Jul 0 0

05-Aug 0 0

13-Aug 0 0

19-Aug 0 0

04-Sep 0 0

16-Sep 0 0

30-Sep 0 0

03-Oct 0 0

07-Oct 0 0

08-Oct 0 0

14-Oct 0 0

15-Oct 0 0

21-Oct 0 0

22-Oct 0 0

28-Oct 0 0.2

29-Oct 0 0

04-Nov 0 0

05-Nov 0 0

11-Nov 0 0

12-Nov 0 0.2

Cornhow - Raw water


18-Nov 0 0

19-Nov 0 0

25-Nov 0 0

26-Nov 0 0.1

02-Dec 0 0

03-Dec 0 0

10-Dec 0 0.1

11-Dec 0 0

16-Dec 0 0

17-Dec 0 0

n 60 60

No. positive 1 5

Min 0 0

Max 0.2 0.2



175

Cornhow - Raw water


1997

07-Jan 0 0

09-Jan 0 0

14-Jan 0 0

16-Jan 0 0

21-Jan 0 0

23-Jan 0 0

28-Jan 0 0

30-Jan 0 0

04-Feb 0 0

06-Feb 0 0

07-Feb 0 0

11-Feb 0 0

12-Feb 0 0

18-Feb 0 0

19-Feb 0 0.1

25-Feb 0 0

05-Mar 0 0

11-Mar 0 0

08-Apr 0 0

09-Apr 0 0

15-Apr 0 0

16-Apr 0 0

23-Apr 0 0

25-Apr 0 0

29-Apr 0 0

30-Apr 0 0

06-May 0 0

07-May 0 0

13-May 0 0.1

14-May 0 0

20-May 0 0.1

21-May 0 0.2

27-May 0 0

03-Jun 0 0.1

04-Jun 0 0

10-Jun 0 0.1

11-Jun 0 0.2

17-Jun 0 0.1

18-Jun 0 0.1

24-Jun 0 0

25-Jun 0 0

01-Jul 0 0

02-Jul 0 0

08-Jul 0 0

09-Jul 0 0

15-Jul 0 0

16-Jul 0.4 0

22-Jul 0 0

29-Jul 0 0

30-Jul 0.2 0

05-Aug 0.3 0

06-Aug 0.1 0.2

12-Aug 0 0

Cornhow - Raw water


13-Aug 0 0

19-Aug 0 0

20-Aug 0 0

26-Aug 0 0

27-Aug 0.1 0.2

02-Sep 0.1 0

03-Sep 0 0

09-Sep 0 0.1

10-Sep 0 0

16-Sep 0 0.3

17-Sep 0 0.2

23-Sep 0 0

24-Sep 0 0

30-Sep 0.2 0

01-Oct 0.1 0

07-Oct 0 0

08-Oct 0 0.2

14-Oct 0 0

15-Oct 0 0

21-Oct 0 0

22-Oct 0 0

28-Oct 0.1 0

29-Oct 0 0.3

04-Nov 0 0

05-Nov 0.2 0

11-Nov 0 0

12-Nov 0 0

18-Nov 0 0

20-Nov 0 0

25-Nov 0 0.2

26-Nov 0 0

03-Dec 0 0

10-Dec 0 0

11-Dec 0 0

17-Dec 0 0

23-Dec 0 0

24-Dec 0 0

30-Dec 0 0

n 91 91

No. positive 10 17

Min 0 0

Max 0.4 0.3



176

Cornhow - Raw water


1998

08-Jan 0 0

13-Jan 0 0

14-Jan 0 0

20-Jan 0 0.1

21-Jan 0 0

27-Jan 0 0

28-Jan 0 0.1

03-Feb 0 0

10-Feb 0 0

11-Feb 0 0

17-Feb 0 0

18-Feb 0 0

24-Feb 0 0.1

25-Feb 0 0

10-Mar 0 0

11-Mar 0 0

17-Mar 0 0.2

18-Mar 0 0.1

25-Mar 0 0

26-Mar 0 0

31-Mar 0 0

01-Apr 0 0

07-Apr 0 0.1

08-Apr 0 0

14-Apr 0 0

15-Apr 0 0

23-Apr 0 0

28-Apr 0 0

29-Apr 0 0.1

05-May 0 0

06-May 0 0

12-May 0 0

13-May 0 0

19-May 0 0

20-May 0 0

26-May 0 0

27-May 0 0

02-Jun 0 0.1

03-Jun 0 0.1

09-Jun 0 0

10-Jun 0 0.1

16-Jun 0 0

17-Jun 0 0

23-Jun 0 0.4

24-Jun 0 0

30-Jun 0 0

01-Jul 0 0

07-Jul 0 0.1

08-Jul 0 0

15-Jul 0 0

Cornhow - Raw water


16-Jul 0 0

21-Jul 0 0.3

22-Jul 0 0

28-Jul 0 0

29-Jul 0 0

04-Aug 0 0

05-Aug 0 0

11-Aug 0 0

12-Aug 0 0

18-Aug 0 0

19-Aug 0 0

25-Aug 0 0

26-Aug 0 0.1

01-Sep 0 0.2

02-Sep 0 0.1

08-Sep 0 0

09-Sep 0 0

15-Sep 0 0

16-Sep 0 0

22-Sep 0 0

23-Sep 0 0

29-Sep 0 0

30-Sep 0 0

06-Oct 0 0

07-Oct 0 0

13-Oct 0 0

14-Oct 0 0

20-Oct 0 0.1

21-Oct 0 0.2

27-Oct 0 0.1

28-Oct 0 0

03-Nov 0 0

04-Nov 0 0

10-Nov 0 0

11-Nov 0 0

17-Nov 0 0.1

18-Nov 0 0

24-Nov 0 0

25-Nov 0 0

01-Dec 0 0

02-Dec 0 0.1

08-Dec 0 0

11-Dec 0 0

15-Dec 0 0

16-Dec 0 0.1

22-Dec 0 0

23-Dec 0 0

29-Dec 0 0

30-Dec 0 0

n 99 99

No. positive 0 22

Min 0 0

Max 0 0.4



177

Cornhow - Raw water


1999

06-Jan 0.1 0

07-Jan 0 0

12-Jan 0 0

13-Jan 0 0

19-Jan 0 0

20-Jan 0.3 0

26-Jan 0 0

27-Jan 0 0.1

02-Feb 0 0

03-Feb 0 0

09-Feb 0 0

10-Feb 0 0

16-Feb 0 0

17-Feb 0 0

23-Feb 0 0.1

24-Feb 0 0

03-Mar 0 0

04-Mar 0 0

09-Mar 0 0

10-Mar 0 0.1

16-Mar 0 0

17-Mar 0 0

23-Mar 0 0.1

24-Mar 0 0

30-Mar 0 0

31-Mar 0 0

06-Apr 0 0

07-Apr 0 0

13-Apr 0 0.1

14-Apr 0.1 0

20-Apr 0 0

21-Apr 0 0.2

27-Apr 0 0.2

28-Apr 0 0

04-May 0 0

05-May 0 0

11-May 0.1 0.1

12-May 0 0

18-May 0 0

19-May 0 0

25-May 0 0

26-May 0 0

01-Jun 0 0.1

02-Jun 0 0

08-Jun 0.1 0

09-Jun 0 0.1

15-Jun 0 0.1

16-Jun 0.1 0

22-Jun 0 0.2

23-Jun 0 0

29-Jun 0 0

30-Jun 0 0

06-Jul 0 0

Cornhow - Raw water


07-Jul 0 0

13-Jul 0 0

14-Jul 0 0

20-Jul 0 0

21-Jul 0 0

27-Jul 0 0

28-Jul 0 0

03-Aug 0 0.2

04-Aug 0 0.1

10-Aug 0 0

12-Aug 0 0

17-Aug 0 0.1

18-Aug 0 0.1

24-Aug 0 0

25-Aug 0 0

31-Aug 0 0.1

01-Sep 0 0

07-Sep 0 0

08-Sep 0 0

14-Sep 0 0

15-Sep 0 0

21-Sep 0 0

28-Sep 0 0

29-Sep 0.1 0.1

05-Oct 0 0

06-Oct 0 0

12-Oct 0 0

13-Oct 0 0

19-Oct 0 0

20-Oct 0 0

26-Oct 0 0

27-Oct 0 0

02-Nov 0 0.3

03-Nov 0 0.1

09-Nov 0 0

16-Nov 0 0

17-Nov 0 0

23-Nov 0 0

24-Nov 0.1 0

25-Nov 0 0

30-Nov 0 0.1

01-Dec 0 0

07-Dec 0.1 0.3

08-Dec 0 0

14-Dec 0 0.1

15-Dec 0 0

21-Dec 0 0

22-Dec 0 0

28-Dec 0 0.2

29-Dec 0 0.2

n 103 103

No. positive 8 25

Min 0 0



178

Cornhow - Raw water


Max 0.3 0.3

2000

04-Jan 0 0

05-Jan 0 0

06-Jan 0 0

07-Jan 0 0

11-Jan 0.1 0.1

12-Jan 0 0.1

13-Jan 0 0.2

14-Jan 0 0

18-Jan 0 0

19-Jan 0 0

20-Jan 0 0

21-Jan 0 0

25-Jan 0 0

26-Jan 0 0

27-Jan 0.1 0

28-Jan 0 0

01-Feb 0 0.2

02-Feb 0 0

03-Feb 0 0

04-Feb 0 0

08-Feb 0 0.1

09-Feb 0.1 0

10-Feb 0 0

11-Feb 0 0

15-Feb 0 0

16-Feb 0 0

17-Feb 0 0.1

18-Feb 0 0

22-Feb 0 0.1

23-Feb 0 0.1

24-Feb 0 0.1

25-Feb 0 0

29-Feb 0 0

01-Mar 0 0.1

02-Mar 0 0.1

03-Mar 0 0

07-Mar 0 0

08-Mar 0 0

09-Mar 0 0.1

10-Mar 0 0.1

14-Mar 0 0.2

15-Mar 0 0

16-Mar 0 0

17-Mar 0.1 0.1

21-Mar 0.2 0.1

22-Mar 0 0

23-Mar 0 0

24-Mar 0 0.1

28-Mar 0 0

29-Mar 0 0.1

30-Mar 0.1 0

04-Apr 0 0.1

05-Apr 0 0

11-Apr 0 0

Cornhow - Raw water


12-Apr 0 0

18-Apr 0 0

19-Apr 0 0

25-Apr 0 0

26-Apr 0 0

02-May 0 0

03-May 0 0

09-May 0 0.1

10-May 0 0

16-May 0 0

17-May 0 0

23-May 0 0

24-May 0 0

30-May 0 0

31-May 0 0

06-Jun 0.1 0.1

07-Jun 0 0.1

13-Jun 0.1 0

14-Jun 0 0.1

20-Jun 0 0

21-Jun 0 0

27-Jun 0 0

28-Jun 0 0

04-Jul 0 0

05-Jul 0 0

11-Jul 0 0

12-Jul 0 0

18-Jul 0 0

19-Jul 0 0

26-Jul 0.3 0.4

01-Aug 0 0.1

02-Aug 0 0

08-Aug 0 0

09-Aug 0 0

15-Aug 0 0

16-Aug 0.4 0.1

22-Aug 0.1 0

23-Aug 0.2 0.1

30-Aug 0 0

01-Sep 0 0.1

05-Sep 0.1 0.1

06-Sep 0 0

12-Sep 0 0

13-Sep 0 0

19-Sep 0 0.2

20-Sep 0 0

26-Sep 0 0

27-Sep 0.2 0.1

03-Oct 0 0

04-Oct 0 0.3

10-Oct 0 0

11-Oct 0.1 0.3

17-Oct 0 0

18-Oct 0 0



179

Cornhow - Raw water


24-Oct 0 0

25-Oct 0 0.1

31-Oct 0.1 1

01-Nov 0 0

07-Nov 0 0.1

08-Nov 0 0

14-Nov 0 0

15-Nov 0 0.1

21-Nov 0 0

22-Nov 0.1 0

28-Nov 0 0

29-Nov 0.1 0

05-Dec 0 0

06-Dec 0.1 0

12-Dec 0.6 1.1

13-Dec 0.1 0.5

19-Dec 0 0.4

20-Dec 0 0.4

27-Dec 0 0.2

28-Dec 0 0

n 128 128

No. positive 21 42

Min 0 0

Max 0.6 1.1

Cornhow - Raw water


2001

02-Jan 0.2 0.2

03-Jan 0 0.3

09-Jan 0.1 0

10-Jan 0 0

16-Jan 0 0

17-Jan 0 0

23-Jan 0 0.1

24-Jan 0.1 0.3

30-Jan 0.2 0

31-Jan 0 0.2

06-Feb 0 0.1

07-Feb 0.4 2

13-Feb 0 0

14-Feb 0 0

20-Feb 0 0

21-Feb 0 0

27-Feb 0 0.2

28-Feb 0.1 0

06-Mar 0 0

07-Mar 0.2 0.1

13-Mar 0 0

14-Mar 0 0.1

20-Mar 0 0

21-Mar 0 0

27-Mar 0 0

28-Mar 0.2 0

02-Apr 0

04-Apr 0 0

06-Apr 0 0

24-Apr 0 0

01-May 0 0

02-May 0 0.1

08-May 0 0

09-May 0 0.1

15-May 0 0

16-May 0 0

22-May 0 0

23-May 0 0

29-May 0 0

30-May 0 0.1

05-Jun 0 0

06-Jun 0 0

12-Jun 0 0

13-Jun 0 0

19-Jun 0 0.1

20-Jun 0 0

26-Jun 0 0

27-Jun 0 0.5

03-Jul 0 0

04-Jul 0 0

10-Jul 0

11-Jul 0 0

17-Jul 0 0



180

Cornhow - Raw water


18-Jul 0 0

24-Jul 0 0

25-Jul 0.1 0.2

31-Jul 0 0

01-Aug 0 0

07-Aug 0 0

08-Aug 0 0

14-Aug 0 0.2

15-Aug 0 0

21-Aug 0 0

22-Aug 0 0.1

28-Aug 0 0

29-Aug 0 0

04-Sep 0 0.1

05-Sep 0 0

11-Sep 0.2 0.1

12-Sep 0 0

18-Sep 0 0

19-Sep 0.1 0

25-Sep 0 0.1

26-Sep 0 0

02-Oct 0.1 0.1

03-Oct 0 0

09-Oct 0 0

10-Oct 0.2 0.5

16-Oct 0 0.1

17-Oct 0 0

23-Oct 0.1 0

24-Oct 0 0

30-Oct 0 0.1

31-Oct 0.1 0.4

06-Nov 0 0

13-Nov 2 7

14-Nov 0 0

20-Nov 0.1 0.1

21-Nov 0 0.1

27-Nov 0 0

28-Nov 0 0

04-Dec 0 0.2

05-Dec 0 0

11-Dec 0 0.1

12-Dec 0 0

18-Dec 0 0

19-Dec 0 0

27-Dec 0 0.1

28-Dec 0 0

31-Dec 0 0.2

n 100 98

No. positive 17 33

Min 0 0

Max 2 7

Cornhow - Raw water


2002

02-Jan 0 0.5

03-Jan 0 0.1

08-Jan 0 0.1

09-Jan 0 0.4

15-Jan 0 0.2

16-Jan 0 0

23-Jan 0 0

28-Jan 0 0

29-Jan 0 0

30-Jan 0 0.1

31-Jan 0 0.2

05-Feb 0 0.1

06-Feb 0 0

12-Feb 0 0

13-Feb 0.1 0.3

19-Feb 0.1 0.3

20-Feb 0 0

26-Feb 0 0.2

27-Feb 0 3

05-Mar 0 0.1

06-Mar 0 0.1

12-Mar 0 0.2

13-Mar 0 0.6

19-Mar 0 0

20-Mar 0 0.1

26-Mar 0 0

27-Mar 0 0.1

02-Apr 0.1 0

03-Apr 0 0

09-Apr 0 0.1

10-Apr 0 0.1

16-Apr 0 0

17-Apr 0 0.2

23-Apr 0 0

24-Apr 0 0

30-Apr 0 0

01-May 0 0

07-May 0.3 0

08-May 0.3 0

14-May 0 0

15-May 0 0

21-May 0 0

22-May 0.1 0

28-May 0 0

29-May 0 0.2

05-Jun 0 0

06-Jun 0 0

12-Jun 0 0.1

18-Jun 0 0

19-Jun 0 0

25-Jun 0 0

26-Jun 0.1 0

02-Jul 0.1 0

03-Jul 0 0

09-Jul 0 0

10-Jul 0 0

16-Jul 0 0

17-Jul 0 0

23-Jul 0 0

24-Jul 0 0

30-Jul 0 0.1

31-Jul 0 0

n 62 62

No. positive 8 24

Min 0 0

Max 0.3 3

End of monitoring programme


Water Supply in Allerdale & Copeland - Monitoring Cryptosporidium - Ennertdale

181

water

tosporidium/L Giardia/L

0 0

0 0

0 0

0 0.1

0 0.1

0 0.1

0 0

0 0

0.3 0

0.3 0.1

0 0

0 0.1

0 0

0 0

0 0

0 0

0 0

0.1 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0.1 0.1

0 0

0 0

0 0.1

0 0

0 0

0 0

0 0

0.1 0

0.2 0

0.1 0.1

0.1 0

0.1 0.1

0.3 1

0 0

0 0.1

0.3 0

0 0

0.1 0

0 0

0 0.1

0 0

0 0.2

0 0

0 0.2

51 51

12 14

0 0

0.3 1

Ennerdale - Raw water

Date Cryptosporidium/L

1996

02-Feb 0

05-Feb 0

12-Feb 0

14-Feb 0

19-Feb 0

21-Feb 0

26-Feb 0

28-Feb 0

07-Mar 0.3

08-Mar 0.3

14-Mar 0

20-Mar 0

25-Mar 0

29-Mar 0

01-Apr 0

03-Apr 0

12-Apr 0

08-May 0.1

09-May 0

15-Jul 0

29-Jul 0

14-Aug 0

19-Aug 0

11-Sep 0

16-Sep 0

23-Sep 0

25-Sep 0.1

02-Oct 0

03-Oct 0

07-Oct 0

09-Oct 0

14-Oct 0

16-Oct 0

21-Oct 0

23-Oct 0.1

28-Oct 0.2

30-Oct 0.1

04-Nov 0.1

06-Nov 0.1

11-Nov 0.3

13-Nov 0

18-Nov 0

20-Nov 0.3

25-Nov 0

27-Nov 0.1

02-Dec 0

04-Dec 0

09-Dec 0

13-Dec 0

16-Dec 0

18-Dec 0

n 51

No Pos 12

Min 0

Max 0.3



1997

06-Jan 0

08-Jan 0

15-Jan 0.1

21-Jan 0

22-Jan 0

27-Jan 0

03-Feb 0

05-Feb 0

10-Feb 0.1

17-Feb 0

20-Feb 0

24-Feb 0

26-Feb 0

05-Mar 0

10-Mar 0

12-Mar 0

07-Apr 0

09-Apr 0

18-Apr 0

21-Apr 0

23-Apr 0

28-Apr 0

30-Apr 0

07-May 0

08-May 0

12-May 0

14-May 0

19-May 0

28-May 0

29-May 0

02-Jun 0

04-Jun 0

09-Jun 0

11-Jun 0

16-Jun 0

18-Jun 0

23-Jun 0

26-Jun 0

07-Jul 0

09-Jul 0.1

14-Jul 0.2

16-Jul 0

21-Jul 0

28-Jul 0

30-Jul 0

04-Aug 0

06-Aug 0

11-Aug 0

13-Aug 0

18-Aug 0

20-Aug 0

27-Aug 0.1

01-Sep 0

03-Sep 0

08-Sep 0

10-Sep 0

Giardia/L

0

0

0

0

0

0

0

0

0.1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.1

0

0

0

0

0

0

0

0.3

0

0

0

0

0

0

0

0

0

0

0

0

0.2

0

0

0

0

0

0.2

0

0

0

0


Water Supply in Allerdale & Copeland - Monitoring Cryptosporidium - Ennerdale

182



15-Sep 0

17-Sep 0

22-Sep 0

24-Sep 0

29-Sep 0

01-Oct 0

06-Oct 0

08-Oct 0.1

13-Oct 0

15-Oct 0

20-Oct 0

22-Oct 0.1

27-Oct 0

29-Oct 0

03-Nov 0.2

05-Nov 0

10-Nov 0.2

12-Nov 1.7

18-Nov 0.2

19-Nov 0

20-Nov 0

21-Nov 0

24-Nov 0.1

26-Nov 0.1

01-Dec 0

05-Dec 0

10-Dec 0

11-Dec 0

17-Dec 0

22-Dec 0

24-Dec 0.2

29-Dec 0

n 88

No Pos 14

Min 0

Max 1.7

y

Giardia/L

0

0

0

0

0

0.1

0

0

0

0.1

0

0.1

0

0

0

0

0.3

0.2

0.3

0.2

0

0

0.2

0.1

0

0.1

0

0

0

0

0

0

88

15

0

0.3



1998

06-Jan 0

12-Jan 0

14-Jan 0

19-Jan 0

21-Jan 0

26-Jan 0

28-Jan 0

02-Feb 0.1

04-Feb 0

09-Feb 0

11-Feb 0

16-Feb 0

18-Feb 0

23-Feb 0

25-Feb 0

02-Mar 0

04-Mar 0.1

09-Mar 0

11-Mar 0

16-Mar 0

18-Mar 0

23-Mar 0

25-Mar 0

30-Mar 0

01-Apr 0

06-Apr 0

08-Apr 0

15-Apr 0

16-Apr 0

20-Apr 0

22-Apr 0.2

27-Apr 0

29-Apr 0

04-May 0

06-May 0

11-May 0

13-May 0

18-May 0

20-May 0

26-May 0

27-May 0

01-Jun 0

03-Jun 0

08-Jun 0.1

10-Jun 0.2

15-Jun 0

17-Jun 0

22-Jun 0.1

24-Jun 0

29-Jun 0

01-Jul 0.2

06-Jul 0

08-Jul 0

13-Jul 0

15-Jul 0

20-Jul 0.6

Giardia/L

0

0

0

0

0

0.1

0

0.1

0

0

0

0

0

0

0

0.1

0.4

0

0

0

0

0.1

0

0.1

0

0.1

0

0

0

0

0

0

0

0

0

0

0

0.1

0

0

0

0

0

0

0

0

0

0

0.1

0.1

0

0.5

0

0.2

0

0



183



22-Jul 0

27-Jul 0

29-Jul 0

03-Aug 0.3

05-Aug 0

10-Aug 0

12-Aug 1

17-Aug 0

19-Aug 0

24-Aug 0

26-Aug 0.2

02-Sep 0

03-Sep 0

07-Sep 0

09-Sep 0

14-Sep 0

16-Sep 0

21-Sep 0

23-Sep 0.1

28-Sep 0

30-Sep 0.3

05-Oct 0.3

07-Oct 0.1

12-Oct 0.1

14-Oct 0

20-Oct 0.5

21-Oct 0.5

26-Oct 0

28-Oct 0

02-Nov 0.3

04-Nov 0.1

10-Nov 0

11-Nov 0

16-Nov 0

18-Nov 0

23-Nov 0

25-Nov 0

30-Nov 0

02-Dec 0

07-Dec 0

09-Dec 0.1

14-Dec 0

16-Dec 0

21-Dec 0

23-Dec 0

29-Dec 0

30-Dec 0

n 103

No Pos 21

Min 0

Max 1

Giardia/L

0

0

0

0

0.1

0.3

0

0

0

0

0

0.1

0

0

0

0.2

0

0

0

0

0

0

0

0

0

0.1

0.1

0.1

0

0

0

0

0

0

0

0.2

0

0

0

0

0

0.1

0.1

0.2

0

0

0

103

23

0

0.5



1999

07-Jan 0

08-Jan 0

11-Jan 0

13-Jan 0

18-Jan 0

20-Jan 0

25-Jan 0

27-Jan 0

01-Feb 0

03-Feb 0

08-Feb 0

10-Feb 0

15-Feb 0

17-Feb 0

22-Feb 0

24-Feb 0

01-Mar 0

03-Mar 0

08-Mar 0

10-Mar 0

15-Mar 0

17-Mar 0

24-Mar 0

25-Mar 0

29-Mar 0

31-Mar 0

07-Apr 0

09-Apr 0

12-Apr 0

14-Apr 0

19-Apr 0.1

21-Apr 0

26-Apr 0

28-Apr 0

03-May 0

05-May 0

10-May 0

12-May 0

17-May 0

19-May 0

25-May 0.1

26-May 0.1

02-Jun 0.2

07-Jun 0

09-Jun 0.3

14-Jun 0

16-Jun 0.3

21-Jun 0

23-Jun 0.1

26-Jul 0

28-Jul 0

02-Aug 0

04-Aug 0

09-Aug 0

11-Aug 0

16-Aug 0

Giardia/L

0.1

0.1

0

0

0.1

0

0

0

0.1

0

0

0

0

0

0.1

0

0

0

0

0

0

0

0

0.2

0

0

0

0.1

0

0.1

0

0

0.1

0

0

0

0

0.2

0

0

0

0

0.1

0

0

0

0

0.1

0

0

0

0

0.2

0.1

0.3

0



184

Giardia/L

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.3

0

0

0

0

0

0

0

0

0

0

0.1

0

0

0.1

0.1

0.1

0

0.1

0

0.3

0.1

0

0

0

95

23

0

0.3



18-Aug 0

23-Aug 0

25-Aug 0

31-Aug 0

01-Sep 0

06-Sep 0

08-Sep 0

13-Sep 0

15-Sep 0

20-Sep 0

22-Sep 0

27-Sep 0

29-Sep 0

04-Oct 0.1

06-Oct 0.7

11-Oct 0.1

13-Oct 0

18-Oct 0.1

20-Oct 0

25-Oct 0

27-Oct 0

01-Nov 0

03-Nov 0

08-Nov 0

10-Nov 0

15-Nov 0

17-Nov 0

22-Nov 0

24-Nov 0.1

29-Nov 0

01-Dec 0

06-Dec 0

08-Dec 0

13-Dec 0

15-Dec 0

20-Dec 0.1

22-Dec 0

29-Dec 0

30-Dec 0

n 95

No Pos 13

Min 0

Max 0.7

w water

yptosporidium/L Giardia/L

0 0

0 0.1

0 0

0 0

0 0

0 0.2

0 0.2

0 0

0 0.1

0 0

0 0

0 0

0 0

0 0

0 0.6

0 0

0 0

0 0

0 0.1

0 0

0 0

0.1 0.1

0 0.1

0 0.1

0 0.1

0 0

0 0.1

0 0

0 0

0 0

0 0.2

0 0

0 0

0.1 0

0 0

0 0

0 0

0 0

0.1 0

0 0

0 0

0 0

0 0.2

0 0

0 0

0 0

0 0

0.3 0

0 0

0 0.1

0 0

0 0

0 0.2

0.4 0.2

0.1 0

0 0.2



2000

04-Jan 0

05-Jan 0

07-Jan 0

11-Jan 0

12-Jan 0

13-Jan 0

14-Jan 0

18-Jan 0

19-Jan 0

25-Jan 0

01-Feb 0

02-Feb 0

08-Feb 0

09-Feb 0

15-Feb 0

16-Feb 0

22-Feb 0

23-Feb 0

03-Mar 0

07-Mar 0

08-Mar 0

14-Mar 0.1

15-Mar 0

21-Mar 0

22-Mar 0

28-Mar 0

29-Mar 0

04-Apr 0

05-Apr 0

11-Apr 0

12-Apr 0

18-Apr 0

19-Apr 0

25-Apr 0.1

26-Apr 0

02-May 0

03-May 0

09-May 0

10-May 0.1

16-May 0

17-May 0

23-May 0

24-May 0

30-May 0

31-May 0

13-Jun 0

14-Jun 0

20-Jun 0.3

21-Jun 0

27-Jun 0

28-Jun 0

04-Jul 0

05-Jul 0

11-Jul 0.4

12-Jul 0.1

18-Jul 0



19-Jul 0

25-Jul 0

26-Jul 0

01-Aug 0

02-Aug 0.1

08-Aug 0.2

09-Aug 0

15-Aug 0.2

16-Aug 0.6

22-Aug 0.1

23-Aug 0

29-Aug 0

30-Aug 0

05-Sep 0

06-Sep 0

12-Sep 0

13-Sep 0.2

19-Sep 0

20-Sep 0

26-Sep 0.1

27-Sep 0

03-Oct 0

04-Oct 0

10-Oct 0

11-Oct 0

17-Oct 0.1

18-Oct 0

24-Oct 0

25-Oct 0

31-Oct 0

01-Nov 0.1

07-Nov 0

08-Nov 0

14-Nov 0

15-Nov 0

21-Nov 0

22-Nov 0.1

28-Nov 0

29-Nov 0

05-Dec 0.2

06-Dec 0

13-Dec 0

19-Dec 0.1

20-Dec 0

27-Dec 0.1

n 101

No Pos 19

Min 0

Max 0.6

Giardia/L

0.1

0

0

0

0

0.1

0.1

0

0

0.1

0

0.1

0

0

0

0.1

0

0

0

0.1

0

0.2

0.1

0.2

0.3

0.3

0

0

0

0.5

0.5

0.5

0.1

0

0.2

0

0

0

0

0.4

0.2

0.2

0.5

0.4

0.1

101

40

0

0.6



185



2001

02-Jan 0.2

03-Jan 0

09-Jan 0

10-Jan 0

17-Jan 0

23-Jan 0

24-Jan 0

30-Jan 0

06-Feb 0

07-Feb 0

13-Feb 0

14-Feb 0

20-Feb 0

21-Feb 0

28-Feb 0.4

05-Mar 0.1

06-Mar 0.1

07-Mar 0

12-Mar 0.2

13-Mar 0

14-Mar 0

19-Mar 0

20-Mar 0

21-Mar 0

26-Mar 0

27-Mar 0

28-Mar 0

04-Apr 0

24-Apr 0.1

25-Apr 0

01-May 0.1

02-May 0

08-May 0

09-May 0

15-May 0

16-May 0

23-May 0

29-May 0

30-May 0.1

05-Jun 0

06-Jun 0

12-Jun 0.1

13-Jun 0

19-Jun 0

20-Jun 0.2

26-Jun 0

27-Jun 0

03-Jul 0

04-Jul 0

10-Jul 0

11-Jul 0.1

17-Jul 0

18-Jul 0

24-Jul 0.1

25-Jul 0

31-Jul 0

Giardia/L

0

0.2

0.5

0

0

0.2

0.1

0.4

0.1

0.1

0

0

0

0

0.8

0.3

0

0

0.3

0

0

0.1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.1

0.2

0.1

0

0.2

0

0

0

0

0

0.3

0.1

0

0



186

yp p

08-Aug 0

09-Aug 0

14-Aug 0

15-Aug 0

21-Aug 0

22-Aug 0

28-Aug 0

29-Aug 0

04-Sep 0

05-Sep 0

11-Sep 0.1

12-Sep 0

18-Sep 0

19-Sep 0

25-Sep 0

26-Sep 0

02-Oct 0.5

03-Oct 0

09-Oct 0.2

10-Oct 0

16-Oct 0

17-Oct 0

23-Oct 0

24-Oct 0.1

30-Oct 0.1

31-Oct 0

06-Nov 0

07-Nov 0.1

13-Nov 0

14-Nov 1

20-Nov 0.1

21-Nov 0

27-Nov 0

28-Nov 0

05-Dec 0

06-Dec 0.1

11-Dec 0

12-Dec 0

18-Dec 0

19-Dec 0

27-Dec 0

28-Dec 0

n 99

No. pos 21

Min 0

Max 1

Giardia/L

0.3

0

0.4

0.1

0.2

0.1

0

0

0

0

0.2

0

0.2

0

0

0

0.1

0

0.1

0

0.1

0

0

0.2

0

0.1

0.2

0.1

3

2

0

0

0

0

0.2

0.2

0.1

0.1

0

0.1

0.2

0.3

93

40

0

3

Giardia/L

0



01-Aug 0

09-Jan 0 0.2

15-Jan 0 0.2

16-Jan 0 0.2

22-Jan 0 0.2

23-Jan 0 0.1

29-Jan 0 0

30-Jan 0 0.1

05-Feb 0 0.1

06-Feb 0 0.2

12-Feb 0 0.4

13-Feb 0 0.4

19-Feb 0 0.2

20-Feb 0 0.1

27-Feb 0 0

05-Mar 0 0

06-Mar 0 0

13-Mar 0 0

14-Mar 0 0.3

19-Mar 0.1 0.3

20-Mar 0 0.1

26-Mar 0 0

27-Mar 0 0.2

02-Apr 0 0.1

03-Apr 0 0.3

09-Apr 0 0

10-Apr 0 0.2

16-Apr 0 0

17-Apr 0 0

23-Apr 0 0.3

24-Apr 0 0

30-Apr 0 0

01-May 0 0.1

07-May 0.1 0.1

08-May 0 0.1

14-May 0 0

15-May 0 0

22-May 0.2 0

28-May 0 0

29-May 0.1 0.1

05-Jun 0.1 0.3

06-Jun 0.1 0

11-Jun 0.1 0

12-Jun 0.1 0.1

18-Jun 0.1 0.1

19-Jun 0 0.3

25-Jun 0 0

26-Jun 0.1 0.1

02-Jul 0 0

03-Jul 0.3 0

09-Jul 0 0

10-Jul 0 0

16-Jul 0 0

17-Jul 0 0

23-Jul 0 0

24-Jul 0 0

30-Jul 0 0

31-Jul 0 0

n 61 61

No. pos 11 31

Min 0 0

Max 0.3 0.4

End of monitoring programme



2002

02-Jan 0 0

03-Jan 0 0

04-Jan 0 0.4

08-Jan 0 0.4

09-Jan 0 0.2




Water Supply in Allerdale & Copeland - Water Sampling Microbiology

187

F. Microbiology

The “spot” or “grab” samples are analysed inaccordance with the company’s qualityprocedures. Up to May of 2000, the companyused membrane filtration and flow cytometryto isolate, identify and enumerateCryptosporidium species oocysts in thesesamples. From May of 2000 the method waschanged to membrane filtration andimmunomagnetic bead separation.Summaries provided by United Utilities ofthe key points for the two methods aredetailed below

Cryptosporidium - Isolation,Identification and Enumeration viamembrane filtration method and flowcytometry [9].

Samples were collected as 10 litre spotsamples of water in plastic containers. During1998/99 the average recovery forCryptosporidium in the YorkshireEnvironmental LEAP Scheme external AQCreport was 64.8% with a minimum recoveryof 33.3%. The whole 10 litre sample wasfiltered through 142 mm membrane filters,1.2 micron pore size at 1.25 litres a minute.The membrane was transferred to a polythenebag and washed with 1% Tween 80. Theresulting eluate was concentrated bycentrifugation at 1500 RCF (RelativeCentrifugal force). Depending on the size ofpellet and amount of material a sucrosegradient may have been carried out with coldsucrose, specific gravity 1.18. AGiardia/Cryptosporidium monoclonalantibody stain was added to the pellet fromcentrifugation in a flow cytometry tube. Thesamples were processed by flow cytometry(Coulter Elite), which sorted theCryptosporidium oocyst and Giardia cyst ‘like’objects onto a microscope slide. The slideswere dried, fixed stained with DAPI and thenexamined by fluorescence microscopy.

Cryptosporidium - Isolation,Identification and Enumeration viamembrane filtration method andimmunomagnetic separation [10].

Samples were collected as 10 litre spotsamples of water in plastic containers.During 1998/99 the average recovery forCryptosporidium in the YorkshireEnvironmental LEAP Scheme external AQCreport was 64.8% with a minimum recoveryof 33.3%.

The whole 10 litre sample was filteredthrough 142 mm membrane filters, 1.2micron pore size at 1.25 litres a minute. Themembrane was transferred to a polythene bagand washed with 1% Tween 80. The resultingeluate was concentrated by centrifugation at1500 RCF (Relative Centrifugal force). If thepellet was greater than 0.5 ml then a sucrosegradient was carried out. If the pellet was lessthan 0.5 ml then no gradient was required.The sucrose gradient was carried out withcold sucrose, specific gravity 1.18. Allsamples were then subject to IMS(Immunomagnetic separation) by theaddition of Dynal GC-Combo beads. Themagnetic beads attach to the oocysts that canthen be separated from the remaining debrisin the sample. The oocysts were thenseparated from the Dynal beads by an acidwash. The remaining suspension was splitbetween wells on a microscope slide andallowed to dry. Once dry, theCryptosporidium/Giardia monoclonalantibody FITC stain followed by DAPI stainwere added to the wells on the microscopeslide before a coverslip was placed on top ofthe microscope slide and the slides visualisedby fluorescence microscopy.


Water Supply in Allerdale & Copeland - Rainfall Data, Cornhow

188

G. Rainfall data

The company collected this on a daily basis,via telemetry, from automated equipmentprovided and maintained by the EnvironmentAgency at Cornhow and Ennerdale WTWs.The records of the total daily rainfallmonitoring at each site have been provided tothe study from January of 1996, apart fromJanuary 1996 to the end of July 1996 forCornhow when the data was provided forweekly rainfall.

The summarised daily rainfall data is detailedin the following tables for each year of thestudy together with total rainfall for eachmonth and comparative data for thelong-term average rainfall for the same monthover the 30-year period 1961 to 1990.

The results of this monitoring are alsosummarised in the graphs for total monthlyrainfall at Cornhow and Ennerdale WTW forthe period of study and the long-term averagerainfall for the same month (Figures 9, 10).



189

Fig

ure

9 R

ain

fall

at

Co

rnh

ow

Wa

ter

Tre

atm

en

t W

ork

s

1 J

an

ua

ry 1

99

6 t

o 3

1 A

ug

us

t 2

00

2

0

50

10

0

15

0

20

0

25

0

30

0

35

0

40

0

Ja

n-1

99

6Ja

n-1

99

7Ja

n-1

99

8Ja

n-1

99

9Ja

n-2

00

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n-2

00

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lete

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or

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nth

(s))

Total monthly rainfall (in mm)

1996

1997

1998

1999

2000

2001

2002

Long term

avera

ge

1961 to 1

990

FIG

UR

E 9

R

AIN

FAL

LA

TC

OR

NH

OW

WA

TE

R T

RE

AT

ME

NT

WO

RK

S1

JAN

UA

RY

1996

TO

31

AU

GU

ST20

02



190

DAILY AND CUMULATIVE RAINFALL AT CRUMMOCK IN MM FOR 1996

Date

mm Total mm Total mm Total mm Total mm Total mm Total

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29 152.8

30 158.3 N/A

31 93.7 86.0 N/A

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 59.7 0.0 71.1 200.4 0.0 0.0

LTA= Long term monthly average rainfall at this site 1961 to 1990

N.B. Data for January to June only available as monthly rainfall, unless not available (N/A)

January February March April May June


Date

mm Total Total Total Total Total Total

1 1.2 1.2 0.6 0.6 1.2 1.2 1.2 1.2 3.0 3.0

2 0.0 1.2 0 0.6 0.8 2.0 13.2 14.4 7.8 10.8

3 0.0 1.2 0 0.6 25 27.0 6.2 20.6 8.4 19.2

4 0.0 1.2 0 0.6 3.2 30.2 16.4 37.0 0.2 19.4

5 0.0 1.2 0 0.6 3.8 34.0 33.2 70.2 0.2 19.6

6 1.8 3.0 0 0.6 1.4 35.4 8 78.2 0.2 19.8

7 0.2 3.2 0 0.6 1.2 36.6 3.2 81.4 0.0 19.8

8 2.2 5.4 0 0.6 0.8 37.4 7.6 89.0 0.0 19.8

9 5.2 10.6 1.6 2.2 0.2 37.6 1.6 90.6 0.0 19.8

10 2.8 13.4 0.0 2.2 0.0 37.6 0.2 90.8 0.2 20.0

11 5.0 18.4 0.2 2.4 41.4 79.0 8.8 99.6 0.0 20.0

12 0.0 18.4 0.0 2.4 3.0 82.0 0.0 99.6 0.2 20.2

13 0.0 18.4 0.0 2.4 0.0 82.0 6.2 105.8 0.2 20.4

14 0.0 18.4 0.0 2.4 26.2 108.2 0.4 106.2 7.6 28.0

15 0.0 18.4 0.0 2.4 25.8 134.0 0.2 106.4 0.6 28.6

16 0.0 18.4 0.0 2.4 12.0 146.0 8.6 115.0 0.0 28.6

17 0.0 18.4 0.0 2.4 4.4 150.4 0.6 115.6 4.2 32.8

18 0.0 18.4 0.0 2.4 13.6 164.0 0.2 115.8 15.0 47.8

19 0.6 19.0 0.0 2.4 1.8 165.8 0.2 116.0 1.0 48.8

20 2.0 21.0 0.0 2.4 5.0 170.8 0.0 116.0 0.0 48.8

21 0.0 21.0 0.0 2.4 0.0 170.8 0.0 116.0 0.0 48.8

22 3.4 24.4 0.0 2.4 0.0 170.8 0.0 116.0 0.0 48.8

23 0.0 24.4 0.0 2.4 0.2 171.0 0.0 116.0 0.0 48.8

24 5.8 30.2 5.0 7.4 22.2 193.2 0.0 116.0 0.0 48.8

25 5.6 35.8 0.0 7.4 31.2 224.4 0.6 116.6 0.0 48.8

26 0.0 35.8 6.4 13.8 21.4 245.8 0.0 116.6 2.2 51.0

27 3.0 38.8 0.6 14.4 7.6 253.4 0.0 116.6 0.0 51.0

28 0.0 38.8 52.0 66.4 8.6 262.0 13.2 129.8 0.0 51.0

29 0.0 38.8 6.2 72.6 1.0 263.0 3.4 133.2 0.4 51.4

30 0.0 38.8 6.0 78.6 15.4 278.4 1.2 134.4 0.2 51.6

31 n/a 0.0 38.8 5.8 284.2 0.0 51.6

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 0.0 29.8 44.4 160.6 81.0 30.9


July August September October November December



191


Date


1 0.0 0.0 3.0 3.0 9.4 9.4 0.0 0.0 0.0 0.0 0.0 0.0

2 0.0 0.0 0.0 3.0 0.0 9.4 2.6 2.6 0.0 0.0 0.0 0.0

3 0.0 0.0 83.2 86.2 0.2 9.6 0.4 3.0 11.8 11.8 0.0 0.0

4 0.0 0.0 1.2 87.4 0.0 9.6 0.8 3.8 40.8 52.6 0.0 0.0

5 0.2 0.2 0.8 88.2 11.0 20.6 3.4 7.2 6.2 58.8 0.0 0.0

6 0.2 0.4 4.4 92.6 0.6 21.2 0.6 7.8 0.8 59.6 2.0 2.0

7 0.0 0.4 0.0 92.6 6.2 27.4 0.0 7.8 7.2 66.8 7.2 9.2

8 0.0 0.4 20.0 112.6 0.0 27.4 0.0 7.8 3.0 69.8 1.0 10.2

9 0.0 0.4 29.0 141.6 0.2 27.6 0.0 7.8 0.0 69.8 1.0 11.2

10 0.2 0.6 2.4 144.0 0.2 27.8 0.0 7.8 14.0 83.8 5.2 16.4

11 1.8 2.4 8.2 152.2 1.0 28.8 0.0 7.8 2.8 86.6 0.0 16.4

12 0.6 3.0 13.6 165.8 1.0 29.8 0.0 7.8 1.8 88.4 0.6 17.0

13 0.0 3.0 0.0 165.8 11.4 41.2 0.0 7.8 0.0 88.4 2.0 19.0

14 0.0 3.0 0.0 165.8 1.0 42.2 0.8 8.6 0.0 88.4 0.8 19.8

15 0.0 3.0 6.0 171.8 0.0 42.2 0.0 8.6 0.0 88.4 0.0 19.8

16 0.0 3.0 26.6 171.8 1.0 43.2 0.0 8.6 3.8 92.2 0.0 19.8

17 2.0 5.0 0.0 171.8 7.2 50.4 0.0 8.6 8.4 100.6 0.0 19.8

18 0.0 5.0 0.0 171.8 6.2 56.6 0.2 8.8 0.2 100.8 5.8 25.6

19 0.0 5.0 0.0 171.8 1.6 58.2 0.0 8.8 10.2 111.0 5.0 30.6

20 0.0 5.0 0.0 171.8 0.6 58.8 0.2 9.0 0.0 111.0 2.2 32.8

21 0.2 5.2 0.0 171.8 1.6 60.4 1.2 10.2 0.0 111.0 0.2 33.0

22 0.2 5.4 0.0 171.8 18.2 78.6 0.0 10.2 0.0 111.0 10.2 43.2

23 0.2 5.6 12.8 184.6 2.8 81.4 13.8 24.0 0.0 111.0 0.0 43.2

24 5.8 11.4 4.6 189.2 0.6 82.0 10.6 34.6 0.0 111.0 1.8 45.0

25 0.2 11.6 6.6 195.8 12.2 94.2 0.0 34.6 0.0 111.0 12.0 57.0

26 0.0 11.6 4.4 200.2 1.8 96.0 0.0 34.6 0.0 111.0 0.6 57.6

27 0.0 11.6 31.2 231.4 12.4 108.4 3.0 37.6 0.0 111.0 1.4 59.0

28 0.2 11.8 0.0 231.4 0.4 108.8 4.8 42.4 0.0 111.0 0.2 59.2

29 0.2 12.0 0.0 108.8 0.0 42.4 0.0 111.0 0.0 59.2

30 0.0 12.0 0.0 108.8 0.0 42.4 0.0 111.0 6.6 65.8

31 0.2 12.2 0.0 108.8 0.0 111.0

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 7.8 246.2 89.9 53.7 135.4 73.1

May JuneJanuary February March April


Date


1 3.4 3.4 1.2 1.2 1.8 1.8 0 0.0 1.8 1.8 0.2 0.2

2 7.4 10.8 0.0 1.2 18 19.8 0 0.0 0 1.8 1.2 1.4

3 6.0 16.8 0.0 1.2 13.6 33.4 0.4 0.4 0 1.8 0.0 1.4

4 0.0 16.8 0.0 1.2 0 33.4 1 1.4 1.4 3.2 0.0 1.4

5 0.6 17.4 0.0 1.2 2.8 36.2 0.6 2.0 8 11.2 42.0 43.4

6 0.0 17.4 0.0 1.2 9.6 45.8 4 6.0 0.4 11.6 13.0 56.4

7 0.0 17.4 0.0 1.2 0 45.8 9 15.0 4.8 16.4 20.0 76.4

8 0.0 17.4 0.0 1.2 n/a 45.8 14 29.0 3.6 20.0 10.4 86.8

9 0.0 17.4 0.0 1.2 n/a 45.8 8.6 37.6 2.6 22.6 22.6 109.4

10 0.0 17.4 0.0 1.2 n/a 45.8 2.6 40.2 13.4 36.0 15.4 124.8

11 0.0 17.4 0.4 1.6 n/a 45.8 0.0 40.2 19.4 55.4 6.2 131.0

12 4.4 21.8 0.0 1.6 n/a 45.8 0.0 40.2 6.4 61.8 0.2 131.2

13 2.4 24.2 11.8 13.4 n/a 45.8 0.0 40.2 1.0 62.8 0.4 131.6

14 0.6 24.8 1.2 14.6 n/a 45.8 5.2 45.4 2.6 65.4 0.0 131.6

15 4.2 29.0 0.4 15.0 n/a 45.8 5.2 50.6 3.0 68.4 0.0 131.6

16 0.4 29.4 0.0 15.0 50.4 96.2 8.0 58.6 5.6 74.0 0.0 131.6

17 0.0 29.4 3.0 18.0 0.0 96.2 0.2 58.8 42.0 116.0 0.4 132.0

18 0.0 29.4 0.0 18.0 0.0 96.2 0.2 59.0 7.8 123.8 5.2 137.2

19 0.0 29.4 1.4 19.4 0.0 96.2 0.0 59.0 4.0 127.8 0.2 137.4

20 0.0 29.4 4.8 24.2 0.0 96.2 0.0 59.0 7.4 135.2 0.2 137.6

21 0.0 29.4 9.2 33.4 0.0 96.2 0.0 59.0 0.0 135.2 0.0 137.6

22 0.0 29.4 0.0 33.4 0.0 96.2 0.0 59.0 0.0 135.2 0.0 137.6

23 n/a 29.4 2.4 35.8 0.0 96.2 0.0 59.0 8.2 143.4 5.6 143.2

24 n/a 29.4 0.0 35.8 0.0 96.2 0.0 59.0 0.0 143.4 17.4 160.6

25 n/a 29.4 1.2 37.0 0.0 96.2 0.0 59.0 0.6 144.0 17.0 177.6

26 n/a 29.4 3.0 40.0 0.0 96.2 0.0 59.0 0.0 144.0 2.6 180.2

27 n/a 29.4 1.6 41.6 0.0 96.2 0.0 59.0 0.0 144.0 12.4 192.6

28 n/a 29.4 4.4 46.0 10.2 106.4 0.0 59.0 12.8 156.8 0.6 193.2

29 n/a 29.4 1.2 47.2 0.0 106.4 1.2 60.2 0.2 157.0 3.2 196.4

30 n/a 29.4 0.6 47.8 4.4 110.8 0.2 60.4 0.0 157.0 21.0 217.4

31 14.4 43.8 8.2 56.0 0.0 60.4 9.0 226.4

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 44.7 43.1 62.6 34.1 94.6 135.6

September October November DecemberJuly August



192


Date


1 24.6 24.6 1.0 1.0 8.2 8.2 0.0 0.0 0.0 0.0 11.2 11.2

2 15.6 40.2 0.0 1.0 35.4 43.6 24.0 24.0 0.0 0.0 28.6 39.8

3 1.2 41.4 1.2 2.2 10.8 54.4 4.0 28.0 0.0 0.0 0.0 39.8

4 14.4 55.8 0.6 2.8 11.2 65.6 3.8 31.8 1.4 1.4 0.0 39.8

5 0.0 55.8 0.6 3.4 4.8 70.4 2.2 34.0 18.8 20.2 3.2 43.0

6 14.8 70.6 17.2 20.6 17.4 87.8 n/a 34.0 5.2 25.4 7.4 50.4

7 7.6 78.2 2.4 23.0 6.0 93.8 n/a 34.0 15.0 40.4 1.4 51.8

8 20.6 98.8 1.0 24.0 0.0 93.8 n/a 34.0 0.0 40.4 9.0 60.8

9 0.0 98.8 8.8 32.8 1.6 95.4 0.6 34.6 0.0 40.4 13.4 74.2

10 0.0 98.8 16.0 48.8 23.8 119.2 0.0 34.6 0.0 40.4 16.6 90.8

11 3.2 102.0 41.4 90.2 0.2 119.4 0.2 34.8 0.8 41.2 0.4 91.2

12 0.8 102.8 0.0 90.2 1.8 121.2 0.2 35.0 0.0 41.2 0.0 91.2

13 20.4 123.2 0.0 90.2 0.0 121.2 0.4 35.4 0.0 41.2 0.0 91.2

14 5.4 128.6 2.2 92.4 0.0 121.2 0.0 35.4 0.0 41.2 3.0 94.2

15 18.4 147.0 3.8 96.2 0.0 121.2 0.0 35.4 0.0 41.2 0.6 94.8

16 9.2 156.2 n/a 96.2 1.2 122.4 3.6 39.0 0.0 41.2 0.0 94.8

17 5.2 161.4 1.2 97.4 0.2 122.6 0.0 39.0 0.0 41.2 0.4 95.2

18 1.4 162.8 0.4 97.8 0.2 122.8 0.0 39.0 0.0 41.2 0.6 95.8

19 0.2 163.0 0.6 98.4 0.0 122.8 2.0 41.0 0.0 41.2 0.0 95.8

20 2.0 165.0 2.2 100.6 0.0 122.8 0.8 41.8 0.0 41.2 1.6 97.4

21 5.0 170.0 13.2 113.8 0.0 122.8 17.4 59.2 0.2 41.4 0.8 98.2

22 6.4 176.4 3.6 117.4 0.0 122.8 14.0 73.2 0.4 41.8 21.2 119.4

23 0.2 176.6 0.0 117.4 6.0 128.8 1.8 75.0 0.4 42.2 31.6 151.0

24 0.0 176.6 0.0 117.4 2.0 130.8 5.2 80.2 4.0 46.2 5.0 156.0

25 0.2 176.8 1.8 119.2 22.4 153.2 2.2 82.4 1.4 47.6 3.6 159.6

26 0.2 177.0 0.2 119.4 2.8 156.0 5.8 88.2 0.0 47.6 13.2 172.8

27 0.0 177.0 8.6 128.0 0.4 156.4 0.2 88.4 4.0 51.6 3.6 176.4

28 0.0 177.0 8.6 136.6 0.0 156.4 0.2 88.6 8.8 60.4 0.6 177.0

29 0.0 177.0 5.4 161.8 0.6 89.2 1.4 61.8 1.0 178.0

30 0.4 177.4 0.2 162.0 0.0 89.2 2.8 64.6 0.0 178.0

31 0.2 177.6 0.0 162.0 0.0 64.6

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 113.1 145.3 133.9 112.9 78.8 197.8



Crummock Rainfall 1998DAILY AND CUMULATIVE RAINFALL AT CRUMMOCK IN MM FOR 1998

Date


1 0.2 0.2 0.0 0.0 17.2 17.2 0 0.0 3 3.0 1.2 1.2

2 0.0 0.2 15.4 15.4 0 17.2 0 0.0 13.6 16.6 0.6 1.8

3 0.0 0.2 38.0 53.4 0 17.2 0 0.0 2.4 19.0 2.0 3.8

4 2.6 2.8 0.0 53.4 0 17.2 0.2 0.2 3.6 22.6 1.6 5.4

5 1.0 3.8 12.0 65.4 0.6 17.8 0.2 0.4 6.2 28.8 0.0 5.4

6 0.2 4.0 11.4 76.8 0.4 18.2 0 0.4 1.2 30.0 0.8 6.2

7 0.2 4.2 2.6 79.4 35.4 53.6 0 0.4 10 40.0 6.6 12.8

8 10.8 15.0 1.4 80.8 23.2 76.8 0 0.4 12.2 52.2 5.2 18.0

9 0.0 15.0 0.0 80.8 27.8 104.6 22.2 22.6 11.4 63.6 0.0 18.0

10 9.2 24.2 0.2 81.0 21.6 126.2 3.0 25.6 0.0 63.6 8.8 26.8

11 1.0 25.2 0.2 81.2 12.2 138.4 10.0 35.6 9.0 72.6 7.0 33.8

12 15.0 40.2 5.4 86.6 8.2 146.6 0.4 36.0 22.8 95.4 6.4 40.2

13 0.6 40.8 8.2 94.8 0.0 146.6 19.6 55.6 2.8 98.2 17.4 57.6

14 3.4 44.2 1.0 95.8 0.6 147.2 2.0 57.6 0.2 98.4 8.4 66.0

15 0.4 44.6 0.0 95.8 1.8 149.0 1.8 59.4 0.0 98.4 0.2 66.2

16 6.2 50.8 28.8 124.6 0.2 149.2 31.8 91.2 0.2 98.6 0.8 67.0

17 2.2 53.0 0.4 125.0 7.4 156.6 8.0 99.2 0.0 98.6 3.2 70.2

18 0.6 53.6 0.0 125.0 1.2 157.8 6.4 105.6 0.2 98.8 12.0 82.2

19 6.6 60.2 1.4 126.4 0.0 157.8 4.0 109.6 1.6 100.4 0.0 82.2

20 8.0 68.2 26.8 153.2 0.0 157.8 40.2 149.8 0.8 101.2 0.0 82.2

21 2.6 70.8 2.8 156.0 0.0 157.8 6.4 156.2 4.0 105.2 1.0 83.2

22 18.8 89.6 0.0 156.0 0.2 158.0 12.0 168.2 5.2 110.4 8.8 92.0

23 0.8 90.4 5.4 161.4 0.0 158.0 5.2 173.4 12.0 122.4 1.8 93.8

24 0.6 91.0 0.0 161.4 0.0 158.0 49.6 223.0 0.0 122.4 13.2 107.0

25 0.0 91.0 3.4 164.8 0.0 158.0 5.4 228.4 21.2 143.6 4.8 111.8

26 0.2 91.2 0.2 165.0 0.0 158.0 30.2 258.6 2.0 145.6 15.2 127.0

27 0.0 91.2 0.0 165.0 0.0 158.0 5.4 264.0 23.0 168.6 7.6 134.6

28 9.8 101.0 0.0 165.0 0.0 158.0 6.8 270.8 1.6 170.2 4.6 139.2

29 11.0 112.0 0.0 165.0 0.0 158.0 7.4 278.2 0.4 170.6 8.4 147.6

30 6.8 118.8 0.0 165.0 2.4 160.4 1.8 280.0 1.6 172.2 2.2 149.8

31 0.8 119.6 0.6 165.6 0.0 280.0 0.6 150.4

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 122.0 127.4 90.6 158.2 103.7 90.1





193


Date


1 18.6 18.6 0.4 0.4 8 8.0 0.4 0.4 0.2 0.2 0 0.0

2 14.0 32.6 0.8 1.2 22.2 30.2 0.8 1.2 0 0.2 15.4 15.4

3 15.8 48.4 1.6 2.8 17.8 48.0 0 1.2 0 0.2 3.2 18.6

4 4.6 53.0 7.4 10.2 5.6 53.6 3.2 4.4 0 0.2 6.4 25.0

5 75.0 128.0 0.8 11.0 0 53.6 20.2 24.6 0.6 0.8 0.8 25.8

6 n/a 128.0 0.6 11.6 7.4 61.0 4.6 29.2 1.4 2.2 0.2 26.0

7 n/a 128.0 0 11.6 2 63.0 1 30.2 21.8 24.0 3.4 29.4

8 0.0 128.0 0.8 12.4 0 63.0 0.4 30.6 9.8 33.8 0 29.4

9 0.2 128.2 0 12.4 0 63.0 7.2 37.8 7 40.8 0 29.4

10 0.2 128.4 0.0 12.4 0.0 63.0 0.2 38.0 14.2 55.0 0.0 29.4

11 8.6 137.0 0.0 12.4 0.8 63.8 23.0 61.0 15.4 70.4 4.6 34.0

12 2.0 139.0 0.4 12.8 0.0 63.8 4.8 65.8 5.2 75.6 0.0 34.0

13 6.2 145.2 3.8 16.6 0.8 64.6 2.2 68.0 1.4 77.0 2.0 36.0

14 18.2 163.4 0.8 17.4 0.0 64.6 7.6 75.6 0.0 77.0 0.0 36.0

15 25.8 189.2 1.0 18.4 0.2 64.8 3.6 79.2 0.0 77.0 0.0 36.0

16 0.0 189.2 0.0 18.4 0.0 64.8 0.0 79.2 0.0 77.0 4.6 40.6

17 5.0 194.2 4.2 22.6 4.0 68.8 0.0 79.2 0.0 77.0 0.2 40.8

18 20.8 215.0 20.4 43.0 0.0 68.8 0.6 79.8 0.0 77.0 0.6 41.4

19 3.8 218.8 0.0 43.0 0.0 68.8 0.8 80.6 0.0 77.0 46.0 87.4

20 4.4 223.2 4.4 47.4 21.0 89.8 20.0 100.6 5.4 82.4 0.0 87.4

21 1.6 224.8 5.0 52.4 2.4 92.2 32.0 132.6 1.4 83.8 0.0 87.4

22 0.0 224.8 0.0 52.4 7.6 99.8 5.6 138.2 3.2 87.0 0.0 87.4

23 10.2 235.0 1.6 54.0 0.6 100.4 0.0 138.2 17.4 104.4 0.0 87.4

24 11.4 246.4 0.0 54.0 3.4 103.8 0.2 138.4 4.2 108.6 0.0 87.4

25 8.6 255.0 4.4 58.4 0.0 103.8 0.0 138.4 6.0 114.6 0.0 87.4

26 4.0 259.0 2.0 60.4 3.8 107.6 1.0 139.4 0.0 114.6 25.0 112.4

27 5.2 264.2 0.0 60.4 0.0 107.6 0.4 139.8 1.6 116.2 8.4 120.8

28 0.6 264.8 10.2 70.6 53.4 161.0 0.0 139.8 11.0 127.2 0.2 121.0

29 1.4 266.2 3.6 164.6 0.0 139.8 0.0 127.2 0.8 121.8

30 0.0 266.2 0.6 165.2 0.0 139.8 0.0 127.2 0.4 122.2

31 0.0 266.2 0.2 165.4 0.0 139.8 0.0 127.2

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 169.6 75.1 136.7 177.0 155.1 135.8

LTA= Long term monthly average rainfall at this site 1961 to 1990 LTA= Long term monthly average rainfall at this s



Date


1 1.4 1.4 1.2 1.2 0.4 0.4 22.6 22.6 24.6 24.6 5.6 5.6

2 2.6 4.0 0 1.2 n/a 0.4 5.2 27.8 3 27.6 33.6 39.2

3 2.4 6.4 1.6 2.8 n/a 0.4 1 28.8 4.6 32.2 9.2 48.4

4 0.2 6.6 0 2.8 n/a 0.4 0 28.8 52.6 84.8 3.2 51.6

5 0 6.6 3.6 6.4 n/a 0.4 0 28.8 25 109.8 50.0 101.6

6 0 6.6 7 13.4 n/a 0.4 12.8 41.6 0 109.8 21.8 123.4

7 0 6.6 0.6 14.0 n/a 0.4 6.6 48.2 7.2 117.0 13.0 136.4

8 0 6.6 0 14.0 17.6 18.0 2.6 50.8 2.2 119.2 18.6 155.0

9 0.8 7.4 0 14.0 0 18.0 1.8 52.6 0 119.2 4.6 159.6

10 0.0 7.4 0.0 14.0 0.0 18.0 5.6 58.2 0.2 119.4 12.4 172.0

11 0.0 7.4 0.0 14.0 0.0 18.0 0.4 58.6 0.2 119.6 10.6 182.6

12 0.0 7.4 5.8 19.8 0.0 18.0 0.2 58.8 0.0 119.6 4.4 187.0

13 10.6 18.0 13.8 33.6 0.6 18.6 n/a 58.8 0.0 119.6 3.0 190.0

14 0.0 18.0 1.2 34.8 0.0 18.6 n/a 58.8 0.0 119.6 2.4 192.4

15 6.6 24.6 3.6 38.4 0.0 18.6 n/a 58.8 3.8 123.4 0.4 192.8

16 2.0 26.6 6.0 44.4 9.8 28.4 n/a 58.8 0.0 123.4 38.4 231.2

17 11.0 37.6 1.2 45.6 4.4 32.8 n/a 58.8 0.2 123.6 0.0 231.2

18 6.0 43.6 9.2 54.8 9.2 42.0 n/a 58.8 0.0 123.6 0.0 231.2

19 15.8 59.4 0.0 54.8 29.2 71.2 n/a 58.8 1.0 124.6 0.0 231.2

20 8.4 67.8 0.0 54.8 6.0 77.2 n/a 58.8 0.0 124.6 10.0 241.2

21 7.0 74.8 0.0 54.8 0.2 77.4 n/a 58.8 2.0 126.6 0.6 241.8

22 0.0 74.8 0.0 54.8 3.2 80.6 n/a 58.8 3.2 129.8 26.2 268.0

23 0.0 74.8 0.0 54.8 4.4 85.0 n/a 58.8 10.6 140.4 23.8 291.8

24 0.6 75.4 0.0 54.8 1.6 86.6 n/a 58.8 140.4 17.2 309.0

25 0.0 75.4 n/a 54.8 0.0 86.6 n/a 58.8 140.4 3.2 312.2

26 0.0 75.4 n/a 54.8 1.0 87.6 n/a 58.8 140.4 8.6 320.8

27 0.0 75.4 0.0 54.8 6.4 94.0 n/a 58.8 140.4 2.0 322.8

28 0.0 75.4 0.0 54.8 15.8 109.8 n/a 58.8 140.4 0.0 322.8

29 0.0 75.4 5.2 60.0 5.8 115.6 n/a 58.8 140.4 12.4 335.2

30 0.0 75.4 2.0 62.0 9.4 125.0 n/a 58.8 140.4 3.0 338.2

31 0.0 75.4 0.0 62.0 n/a 58.8 6.4 344.6

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 76.9 47.7 70.6 27.2 84.6 206.3

site 1961 to 1990

July August DecemberSeptember NovemberOctober



194

DAILY AND CUMULATIVE RAINFALL AT CRUMMOCK IN mm FOR 2000

Date


1 0.6 0.6 8.4 8.4 16.8 16.8 0.6 0.6 0 0.0 13 13.0

2 13.8 14.4 0.8 9.2 28.4 45.2 3.6 4.2 0.2 0.2 5.4 18.4

3 0.8 15.2 13.6 22.8 0.0 45.2 0.2 4.4 0 0.2 19 37.4

4 n/a 15.2 3.8 26.6 0.2 45.4 0 4.4 0 0.2 4.2 41.6

5 11.4 26.6 8.2 34.8 10.8 56.2 0 4.4 0 0.2 6.6 48.2

6 4.2 30.8 8.4 43.2 10.4 66.6 0 4.4 0 0.2 4.4 52.6

7 17.2 48.0 16.2 59.4 10.2 76.8 1 5.4 0 0.2 1.6 54.2

8 0.0 48.0 8 67.4 0.0 76.8 0 5.4 0 0.2 1.4 55.6

9 0.0 48.0 29 96.4 0.0 76.8 0 5.4 0 0.2 15.2 70.8

10 13.2 61.2 0.2 96.6 0.0 76.8 11.8 17.2 0 0.2 4.6 75.4

11 48.6 109.8 10.6 107.2 0.0 76.8 9.4 26.6 0 0.2 0.2 75.6

12 11.8 121.6 0.2 107.4 0.0 76.8 5.4 32.0 0 0.2 4.4 80.0

13 0.6 122.2 1.6 109.0 0.0 76.8 7.2 39.2 0 0.2 1.2 81.2

14 0.0 122.2 1 110.0 0.0 76.8 0.2 39.4 0 0.2 0 81.2

15 0.0 122.2 10.2 120.2 0.0 76.8 0 39.4 0.2 0.4 0 81.2

16 0.0 122.2 1.8 122.0 0.0 76.8 5.2 44.6 16.4 16.8 0 81.2

17 0.2 122.4 5.6 127.6 0.2 77.0 6.2 50.8 18.8 35.6 0 81.2

18 0.0 122.4 5.4 133.0 0.0 77.0 0.6 51.4 2.4 38.0 0 81.2

19 1.0 123.4 0 133.0 0.0 77.0 10.8 62.2 2.8 40.8 0.4 81.6

20 0.2 123.6 8.6 141.6 0.0 77.0 6.8 69.0 2 42.8 7.2 88.8

21 0.4 124.0 0.8 142.4 0.2 77.2 4.4 73.4 0.8 43.6 17.0 105.8

22 0.0 124.0 0.2 142.6 0.0 77.2 0.2 73.6 0.8 44.4 6.4 112.2

23 1.6 125.6 7.2 149.8 6.2 83.4 0.8 74.4 5 49.4 7 119.2

24 0.0 125.6 3.8 153.6 3.4 86.8 3.6 78.0 1.6 51.0 0.4 119.6

25 0.2 125.8 0 153.6 0.0 86.8 2 80.0 0.4 51.4 0 119.6

26 1.6 127.4 26.8 180.4 0.2 87.0 8.4 88.4 7.2 58.6 0 119.6

27 4.4 131.8 21.6 202.0 1.4 88.4 0 88.4 1 59.6 0 119.6

28 29.4 161.2 8.4 210.4 0.0 88.4 0.2 88.6 1.4 61.0 0 119.6

29 1.8 163.0 2.2 212.6 0.0 88.4 0 88.6 1 62.0 0.2 119.8

30 20.0 183.0 0.0 88.4 0 88.6 0.2 62.2 0.4 120.2

31 31.0 214.0 0.4 88.8 3.8 66.0

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 136.3 226.2 73.4 112.2 80.5 133.6




Date


1 0.2 0.2 6.8 6.8 5.2 5.2 3.8 3.8 13.8 13.8 25.6 25.6

2 5.8 6.0 5.8 12.6 0 5.2 1.8 5.6 6.6 20.4 5.0 30.6

3 0 6.0 3.2 15.8 0 5.2 9.6 15.2 9.2 29.6 16.4 47.0

4 0 6.0 0 15.8 19.8 25.0 15 30.2 4.8 34.4 13.2 60.2

5 4.2 10.2 0.8 16.6 13 38.0 0.2 30.4 9.4 43.8 16.6 76.8

6 0 10.2 0.2 16.8 3.2 41.2 8.8 39.2 14.8 58.6 1.6 78.4

7 2.2 12.4 1.6 18.4 7.2 48.4 9.6 48.8 12.2 70.8 14.8 93.2

8 21.2 33.6 1.2 19.6 0 48.4 0 48.8 13.4 84.2 41.6 134.8

9 25.4 59.0 12.2 31.8 2.6 51.0 2.4 51.2 0.0 84.2 10.0 144.8

10 0.4 59.4 0 31.8 0.6 51.6 20.4 71.6 8.0 92.2 7.0 151.8

11 0 59.4 0 31.8 1.0 52.6 2.4 74.0 32.6 124.8 27.6 179.4

12 0.8 60.2 8.2 40.0 0.6 53.2 1 75.0 13.2 138.0 25.0 204.4

13 1.6 61.8 18 58.0 1.2 54.4 6.8 81.8 1.0 139.0 3.4 207.8

14 0 61.8 4.8 62.8 1.2 55.6 0.2 82.0 0.0 139.0 0.8 208.6

15 0 61.8 1.4 64.2 2.6 58.2 0 82.0 11.4 150.4 0.0 208.6

16 0 61.8 0.4 64.6 0.4 58.6 3.4 85.4 16.8 167.2 0.6 209.2

17 0 61.8 0 64.6 21.4 80.0 9.2 94.6 1.4 168.6 0.0 209.2

18 0 61.8 4.6 69.2 1.2 81.2 5.6 100.2 15.2 183.8 0.0 209.2

19 0 61.8 0 69.2 17 98.2 1.8 102.0 1.2 185.0 6.4 215.6

20 0 61.8 0.6 69.8 6.8 105.0 3 105.0 0.2 185.2 0.0 215.6

21 0 61.8 4.0 73.8 9.2 114.2 0 105.0 1.8 187.0 0.0 215.6

22 0 61.8 0 73.8 1.2 115.4 8.6 113.6 4.4 191.4 0.0 215.6

23 0 61.8 0 73.8 0 115.4 14 127.6 4.2 195.6 1.4 217.0

24 0 61.8 0 73.8 29.4 144.8 48.4 176.0 12.6 208.2 0.0 217.0

25 0 61.8 7.4 81.2 0.4 145.2 2.2 178.2 31.2 239.4 0.0 217.0

26 0 61.8 2.8 84.0 20.6 165.8 8 186.2 12.0 251.4 0.0 217.0

27 0 61.8 1 85.0 25.2 191.0 2.2 188.4 10.2 261.6 0.2 217.2

28 0 61.8 0 85.0 0.2 191.2 12 200.4 30.2 291.8 1.0 218.2

29 0 61.8 0 85.0 0 191.2 10.8 211.2 4.8 296.6 1.0 219.2

30 1.4 63.2 0 85.0 0.8 192.0 5 216.2 13.6 310.2 2.0 221.2

31 14.4 77.6 10.4 95.4 11.4 227.6 17.0 238.2

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 79.2 73.4 108.5 128.6 186.9 142.6





195


Date


1 6.0 6.0 5.0 5.0 0.0 0.0 0.8 0.8 0.2 0.2 11.2 11.2

2 4.4 10.4 8.0 13.0 0.0 0.0 3.4 4.2 0.6 0.8 0.2 11.4

3 21.4 31.8 3.8 16.8 0.0 0.0 3.4 7.6 0.0 0.8 0.0 11.4

4 0.0 31.8 8.6 25.4 0.0 0.0 0.4 8.0 0.0 0.8 0.0 11.4

5 1.8 33.6 8.0 33.4 0.0 0.0 7.2 15.2 0.0 0.8 2.0 13.4

6 4.8 38.4 7.2 40.6 9.0 9.0 14.6 29.8 0.0 0.8 18.0 31.4

7 5.8 44.2 0.0 40.6 0.0 9.0 4.0 33.8 0.0 0.8 0.0 31.4

8 0.0 44.2 0.0 40.6 6.4 15.4 0.2 34.0 0.0 0.8 11.0 42.4

9 0.0 44.2 2.4 43.0 2.6 18.0 16.6 50.6 0.0 0.8 2.0 44.4

10 0.2 44.4 14.8 57.8 1.6 19.6 0.8 51.4 0.0 0.8 0.2 44.6

11 0.0 44.4 0.0 57.8 8.0 27.6 0.0 51.4 0.0 0.8 0.4 45.0

12 0.0 44.4 0.0 57.8 0.0 27.6 0.0 51.4 0.0 0.8 0.0 45.0

13 0.0 44.4 0.2 58.0 0.0 27.6 0.6 52.0 0.4 1.2 0.0 45.0

14 0.0 44.4 0.2 58.2 0.0 27.6 1.0 53.0 1.6 2.8 4.4 49.4

15 0.0 44.4 0.0 58.2 0.0 27.6 0.4 53.4 10.8 13.6 7.6 57.0

16 0.0 44.4 0.0 58.2 0.0 27.6 1.2 54.6 2.0 15.6 0.0 57.0

17 0.2 44.6 0.2 58.4 0.0 27.6 3.0 57.6 15.0 30.6 0.0 57.0

18 0.0 44.6 1.0 59.4 0.0 27.6 0.0 57.6 0.2 30.8 0.2 57.2

19 0.0 44.6 0.0 59.4 0.0 27.6 1.2 58.8 0.0 30.8 11.8 69.0

20 0.6 45.2 0.6 60.0 0.0 27.6 0.0 58.8 0.0 30.8 0.0 69.0

21 0.4 45.6 0.2 60.2 7.0 34.6 4.0 62.8 0.0 30.8 0.0 69.0

22 10.4 56.0 3.2 63.4 1.4 36.0 3.0 65.8 0.0 30.8 0.0 69.0

23 17.6 73.6 0.0 63.4 3.4 39.4 0.0 65.8 0.0 30.8 0.0 69.0

24 5.0 78.6 0.2 63.6 0.2 39.6 4.8 70.6 0.0 30.8 0.0 69.0

25 13.8 92.4 2.4 66.0 0.0 39.6 0.4 71.0 1.8 32.6 3.2 72.2

26 6.4 98.8 4.6 70.6 0.4 40.0 0.6 71.6 1.2 33.8 6.2 78.4

27 0.0 98.8 3.2 73.8 4.2 44.2 8.0 79.6 2.4 36.2 2.6 81.0

28 0.8 99.6 0.8 74.6 0.0 44.2 4.0 83.6 2.4 38.6 5.4 86.4

29 0.0 99.6 1.2 45.4 8.8 92.4 1.2 39.8 3.2 89.6

30 3.8 103.4 16.6 62.0 0.2 92.6 5.8 45.6 1.4 91.0

31 0.0 103.4 1.6 63.6 2.4 48.0

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 65.9 79.4 52.6 117.2 58.5 101.1




Date


1 0.0 0.0 0.4 0.4 2.2 2.2 0.6 0.6 0.8 0.8 0.4 0.4

2 0.8 0.8 0.4 0.8 2.0 4.2 6.4 7.0 2.8 3.6 0.2 0.6

3 19.0 19.8 0.8 1.6 1.5 5.7 5.6 12.6 0.2 3.8 24.0 24.6

4 0.0 19.8 2.4 4.0 0.2 5.9 9.2 21.8 2.8 6.6 2.6 27.2

5 0.0 19.8 2.4 6.4 4.8 10.7 22.0 43.8 15.4 22.0 4.4 31.6

6 1.8 21.6 0.6 7.0 0.2 10.9 14.8 58.6 7.6 29.6 2.6 34.2

7 0.4 22.0 15.6 22.6 1.8 12.7 39.0 97.6 16.0 45.6 3.6 37.8

8 3.4 25.4 1.8 24.4 0.0 12.7 16.6 114.2 0.8 46.4 0.0 37.8

9 4.8 30.2 0.2 24.6 0.0 12.7 9.8 124.0 0.4 46.8 0.2 38.0

10 14.2 44.4 1.4 26.0 0.2 12.9 3.4 127.4 0.8 47.6 0.2 38.2

11 4.4 48.8 11.4 37.4 0.0 12.9 15.2 142.6 11.0 58.6 0.2 38.4

12 1.0 49.8 10.8 48.2 31.8 44.7 0.6 143.2 1.0 59.6 0.2 38.6

13 1.2 51.0 1.0 49.2 10.8 55.5 8.0 151.2 3.0 62.6 0.0 38.6

14 9.4 60.4 0.4 49.6 8.4 63.9 11.2 162.4 0.0 62.6 0.0 38.6

15 0.2 60.6 10.4 60.0 5.2 69.1 5.8 168.2 0.0 62.6 0.0 38.6

16 3.4 64.0 1.6 61.6 1.8 70.9 0.0 168.2 0.0 62.6 0.0 38.6

17 0.2 64.2 0.2 61.8 0.0 70.9 10.4 178.6 0.0 62.6 1.4 40.0

18 0.0 64.2 8.2 70.0 0.0 70.9 0.4 179.0 0.8 63.4 0.4 40.4

19 0.0 64.2 13.2 83.2 5.8 76.7 4.0 183.0 1.0 64.4 0.4 40.8

20 0.4 64.6 0.0 83.2 0.6 77.3 1.0 184.0 2.2 66.6 3.2 44.0

21 1.8 66.4 5.4 88.6 0.0 77.3 15.0 199.0 13.0 79.6 4.8 48.8

22 0.2 66.6 0.0 88.6 0.0 77.3 0.4 199.4 0.0 79.6 0.0 48.8

23 2.2 68.8 0.6 89.2 0.6 77.9 18.2 217.6 2.2 81.8 8.4 57.2

24 0.4 69.2 0.6 89.8 4.4 82.3 8.8 226.4 10.6 92.4 2.8 60.0

25 0.0 69.2 5.2 95.0 7.8 90.1 10.2 236.6 2.2 94.6 0.0 60.0

26 0.0 69.2 0.0 95.0 5.8 95.9 17.4 254.0 8.2 102.8 9.8 69.8

27 0.0 69.2 0.0 95.0 30.6 126.5 1.4 255.4 13.4 116.2 3.4 73.2

28 0.0 69.2 0.0 95.0 8.0 134.5 0.0 255.4 32.2 148.4 0.6 73.8

29 0.0 69.2 6.0 101.0 1.4 135.9 0.0 255.4 3.6 152.0 0.6 74.4

30 3.0 72.2 1.0 102.0 22.2 158.1 4.4 259.8 10.4 162.4 0.4 74.8

31 0.0 72.2 0.0 102.0 0.0 259.8 0.6 75.4

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 73.7 78.5 89.3 146.8 97.8 45.1


NovemberJuly DecemberAugust September October



196


Date


1 0.4 0.4 12.8 12.8 0.6 0.6 13.4 13.4 0.6 0.6 1.2 1.2

2 0.6 1.0 11.0 23.8 0.8 1.4 1.6 15.0 1.2 1.8 7.4 8.6

3 0.0 1.0 6.4 30.2 0.0 1.4 1.2 16.2 0.0 1.8 8.2 16.8

4 1.0 2.0 13.6 43.8 0.2 1.6 0.2 16.4 1.0 2.8 0.8 17.6

5 0.2 2.2 7.4 51.2 20.6 22.2 0.0 16.4 0.0 2.8 21 38.6

6 0.2 2.4 15.0 66.2 2.4 24.6 0.0 16.4 0.0 2.8 0 38.6

7 0.0 2.4 11.6 77.8 0.2 24.8 0.0 16.4 7.4 10.2 0 38.6

8 0.0 2.4 11.2 89.0 9.2 34.0 0.0 16.4 0.0 10.2 9.8 48.4

9 0.0 2.4 7.6 96.6 20.2 54.2 0.0 16.4 0.0 10.2 14.2 62.6

10 0.2 2.6 31.0 127.6 1.4 55.6 0.0 16.4 0.0 10.2 9.6 72.2

11 6.4 9.0 3.4 131.0 0.0 55.6 1.0 17.4 0.0 10.2 1.6 73.8

12 7.6 16.6 4.8 135.8 0.0 55.6 0.0 17.4 0.4 10.6 5 78.8

13 10.0 26.6 0.0 135.8 0.4 56.0 0.8 18.2 19.0 29.6 7.6 86.4

14 11.0 37.6 0.4 136.2 0.4 56.4 2.8 21.0 4.0 33.6 20.6 107.0

15 0.0 37.6 0.0 136.2 1.2 57.6 0.0 21.0 1.8 35.4 1.6 108.6

16 39.2 76.8 0.0 136.2 2.0 59.6 0.0 21.0 0.0 35.4 3.8 112.4

17 1.8 78.6 3.4 139.6 1.2 60.8 0.0 21.0 4.6 40.0 0 112.4

18 7.2 85.8 5.6 145.2 0.0 60.8 1.0 22.0 6.8 46.8 0 112.4

19 9.4 95.2 26.0 171.2 2.8 63.6 0.6 22.6 17.2 64.0 0 112.4

20 1.4 96.6 3.8 175.0 5.0 68.6 9.2 31.8 8.4 72.4 0 112.4

21 25.6 122.2 26.2 201.2 0.4 69.0 14.0 45.8 7.8 80.2 5.8 118.2

22 11.0 133.2 5.4 206.6 0.0 69.0 0.0 45.8 12.2 92.4 1.8 120.0

23 8.4 141.6 5.4 212.0 0.0 69.0 0.0 45.8 8.8 101.2 0.2 120.2

24 0.0 141.6 4.8 216.8 7.0 76.0 0.8 46.6 33.0 134.2 1.4 121.6

25 23.8 165.4 44.0 260.8 1.6 77.6 25.4 72.0 8.8 143.0 1.4 123.0

26 0.0 165.4 2.0 262.8 0.0 77.6 8.8 80.8 8.0 151.0 2.2 125.2

27 1.4 166.8 17.8 280.6 0.0 77.6 4.4 85.2 0.0 151.0 0 125.2

28 10.4 177.2 3.0 283.6 0.0 77.6 17.4 102.6 8 159.0 0 125.2

29 14.8 192.0 0.0 77.6 10.0 112.6 1.8 160.8 1.4 126.6

30 1.2 193.2 4.2 81.8 4.4 117.0 3 163.8 18.6 145.2

31 35.6 228.8 11.4 93.2 0 163.8

LTA 157.0 94.0 121.0 79.0 82.0 90.0

1961-90

% LTA 145.7 301.7 77.0 148.1 199.8 161.3



Date


1 16.8 16.8 1.4 1.4

2 0.8 17.6 14.8 16.2

3 0.8 18.4 0.2 16.4

4 6 24.4 0.2 16.6

5 0.2 24.6 0 16.6

6 0.2 24.8 0.2 16.8

7 3.8 28.6 14.6 31.4

8 0 28.6 0 31.4

9 3.8 32.4 1 32.4

10 8.8 41.2 0 32.4

11 10 51.2 0.8 33.2

12 0.4 51.6 13.6 46.8

13 0 51.6 8.6 55.4

14 0 51.6 6 61.4

15 0 51.6 0 61.4

16 0 51.6 0 61.4

17 0 51.6 5.2 66.6

18 11.4 63.0 4.8 71.4

19 6.2 69.2 0 71.4

20 5 74.2 0 71.4

21 0.8 75.0 0 71.4

22 9.8 84.8 0 71.4

23 3.2 88.0 13.8 85.2

24 0.2 88.2 0.6 85.8

25 1 89.2 0 85.8

26 0 89.2 0 85.8

27 0 89.2 0 85.8

28 0 89.2 4.6 90.4

29 0 89.2 1.2 91.6

30 3 92.2 17.4 109.0

31 2.4 94.6 0.0 109.0

LTA 98.0 130.0 177.0 177.0 166.0 167.0

1961-90

% LTA 96.5 83.8 0.0 0.0 0.0 0.0



Water Supply in Allerdale & Copeland - Rainfall Data, Ennerdale

197

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Total monthly rainfall (in mm)

1996

1997

1998

1999

2000

2001

2002

Long term

avera

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1961 to 1

990

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1996

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198

DAILY AND CUMULATIVE RAINFALL AT ENNERDALE IN MM FOR 1996

Date


1 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 1.4 1.4 0.4 0.4

2 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4 0.0 0.4

3 4.6 4.8 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.6 18.6 19.0

4 9.0 13.8 6.4 6.4 0.0 0.0 0.0 0.0 0.0 1.6 3.6 22.6

5 5.0 18.8 1.2 7.6 0.0 0.0 0.0 0.0 0.0 1.6 1.0 23.6

6 6.2 25.0 0.0 7.6 0.0 0.0 0.0 0.0 0.0 1.6 0.0 23.6

7 7.4 32.4 0.0 7.6 0.0 0.0 0.2 0.2 0.0 1.6 0.8 24.4

8 12.2 44.6 1.8 9.4 0.0 0.0 1.6 1.8 0.0 1.6 0.0 24.4

9 13.4 58.0 49.8 59.2 0.0 0.0 1.6 3.4 0.0 1.6 14.2 38.6

10 0.4 58.4 9.8 69.0 0.0 0.0 2.6 6.0 0.8 2.4 6.2 44.8

11 3.2 61.6 30.0 99.0 32.0 32.0 1.4 7.4 0.0 2.4 12.0 56.8

12 21.8 83.4 1.2 100.2 3.2 35.2 0.0 7.4 0.0 2.4 0.2 57.0

13 10.8 94.2 0.0 100.2 1.0 36.2 0.0 7.4 0.0 2.4 0.0 57.0

14 1.4 95.6 0.0 100.2 0.8 37.0 2.4 9.8 0.0 2.4 0.4 57.4

15 1.2 96.8 0.8 101.0 1.2 38.2 11.6 21.4 0.0 2.4 0.0 57.4

16 0.0 96.8 3.0 104.0 4.0 42.2 17.6 39.0 0.0 2.4 0.0 57.4

17 0.0 96.8 18.4 122.4 0.0 42.2 18.4 57.4 0.0 2.4 0.0 57.4

18 0.0 96.8 0.4 122.8 0.0 42.2 0.2 57.6 1.2 3.6 0.0 57.4

19 0.0 96.8 1.0 123.8 0.0 42.2 0.8 58.4 9.6 13.2 0.0 57.4

20 0.0 96.8 0.2 124.0 0.0 42.2 1.4 59.8 2.8 16.0 0.0 57.4

21 0.0 96.8 6.8 130.8 0.0 42.2 7.4 67.2 4.0 20.0 0.0 57.4

22 0.0 96.8 1.6 132.4 0.0 42.2 14.0 81.2 10.8 30.8 0.0 57.4

23 0.0 96.8 19.4 151.8 0.0 42.2 8.6 89.8 1.6 32.4 0.0 57.4

24 0.0 96.8 5.6 157.4 0.0 42.2 6.6 96.4 0.4 32.8 0.0 57.4

25 0.0 96.8 1.6 159.0 0.0 42.2 15.2 111.6 0.2 33.0 2.2 59.6

26 0.0 96.8 7.4 166.4 0.0 42.2 1.2 112.8 12.0 45.0 0.0 59.6

27 0.6 97.4 0.0 166.4 0.0 42.2 0.2 113.0 0.0 45.0 5.0 64.6

28 0.4 97.8 0.0 166.4 0.0 42.2 1.8 114.8 41.0 86.0 12.0 76.6

29 0.0 97.8 0.0 166.4 0.0 42.2 0.2 115.0 3.4 89.4 1.4 78.0

30 0.0 97.8 0.0 42.2 10.2 125.2 1.6 91.0 1.4 79.4

31 0.2 98.0 0.0 42.2 0.0 91.0

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 55.7 147.3 28.3 124.0 92.9 68.4



Date


1 0.2 0.2 1.8 1.8 1.0 1.0 2.0 2.0 1.2 1.2 2.0 2.0

2 29.0 29.2 0.0 1.8 0.0 1.0 0.6 2.6 6.6 7.8 6.0 8.0

3 10.0 39.2 0.0 1.8 0.2 1.2 17.4 20.0 6.2 14.0 8.2 16.2

4 5.0 44.2 0.0 1.8 0.0 1.2 2.2 22.2 12.6 26.6 0.4 16.6

5 0.2 44.4 0.0 1.8 0.0 1.2 3.4 25.6 31.4 58.0 0.0 16.6

6 0.0 44.4 3.0 4.8 0.0 1.2 2.4 28.0 1.2 59.2 0.4 17.0

7 0.0 44.4 1.6 6.4 0 1.2 1.4 29.4 0.6 59.8 0.4 17.4

8 1.6 46.0 3.6 10.0 0 1.2 0.4 29.8 4 63.8 0.2 17.6

9 0.2 46.2 8.6 18.6 0 1.2 0 29.8 1.8 65.6 0.2 17.8

10 0.0 46.2 12.8 31.4 0.0 1.2 0.2 30.0 0.0 65.6 0.2 18.0

11 18.2 64.4 0.8 32.2 0.0 1.2 47.0 77.0 8.6 74.2 0.0 18.0

12 0.4 64.8 0.0 32.2 0.0 1.2 4.4 81.4 0.0 74.2 0.0 18.0

13 6.4 71.2 0.0 32.2 0.0 1.2 0.4 81.8 4.6 78.8 0.2 18.2

14 0.0 71.2 0.0 32.2 0.0 1.2 34.6 116.4 0.6 79.4 4.4 22.6

15 0.0 71.2 0.0 32.2 0.0 1.2 28.8 145.2 0.6 80.0 0.6 23.2

16 0.0 71.2 0.0 32.2 0.0 1.2 15.2 160.4 7.0 87.0 0.2 23.4

17 0.0 71.2 0.0 32.2 0.0 1.2 7.8 168.2 1.2 88.2 3.0 26.4

18 0.0 71.2 0.0 32.2 0.0 1.2 19.6 187.8 0.2 88.4 14.4 40.8

19 0.0 71.2 1.0 33.2 0.0 1.2 2.2 190.0 6.6 95.0 0.6 41.4

20 0.0 71.2 2.0 35.2 0.0 1.2 8.2 198.2 0.4 95.4 0.0 41.4

21 0.2 71.4 0.2 35.4 0.0 1.2 0.0 198.2 0.6 96.0 0.0 41.4

22 0.0 71.4 4.4 39.8 0.0 1.2 0.2 198.4 1.0 97.0 0.0 41.4

23 5.2 76.6 2.0 41.8 0.0 1.2 0.4 198.8 1.2 98.2 0.0 41.4

24 0.0 76.6 8.2 50.0 9.0 10.2 21.8 220.6 22.0 120.2 0.0 41.4

25 4.8 81.4 4.6 54.6 0.4 10.6 24.0 244.6 0.0 120.2 0.2 41.6

26 0.4 81.8 5.6 60.2 9.0 19.6 23.0 267.6 0.0 120.2 6.6 48.2

27 0.0 81.8 1.4 61.6 0.6 20.2 12.4 280.0 0.2 120.4 0.2 48.4

28 7.2 89.0 0.0 61.6 55.6 75.8 7.0 287.0 23.0 143.4 0.0 48.4

29 0.0 89.0 0.0 61.6 11.0 86.8 0.8 287.8 5.2 148.6 0.6 49.0

30 3.4 92.4 0.0 61.6 4.8 91.6 30.6 318.4 5.0 153.6 0.2 49.2

31 0.8 93.2 0.0 61.6 4.4 322.8 0.0 49.2

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 72.8 37.6 49.8 153.0 85.8 27.3




199


Date


1 0.5 0.5 4.4 4.4 5.6 5.6 0.0 0.0 0.0 0.0 0.0 0.0

2 0.0 0.5 0.2 4.6 0.0 5.6 1.2 1.2 0.0 0.0 0.0 0.0

3 0.0 0.5 51.4 56.0 0.0 5.6 0.6 1.8 27.8 27.8 0.0 0.0

4 0.0 0.5 1.2 57.2 0.4 6.0 2.6 4.4 36.4 64.2 0.0 0.0

5 0.0 0.5 0.2 57.4 13.4 19.4 4.2 8.6 6.4 70.6 0.4 0.4

6 0.0 0.5 1.8 59.2 1.0 20.4 0.0 8.6 0.6 71.2 2.2 2.6

7 0.0 0.5 0.0 59.2 5.4 25.8 0.0 8.6 8.0 79.2 7.8 10.4

8 0.0 0.5 18.2 77.4 0.2 26.0 0.0 8.6 0.2 79.4 0.6 11.0

9 0.0 0.5 15.4 92.8 0.4 26.4 0.0 8.6 0.0 79.4 1.4 12.4

10 0.5 1.0 1.2 94.0 0.2 26.6 0.0 8.6 24.4 103.8 5.2 17.6

11 2.0 3.0 9.2 103.2 1.6 28.2 0.0 8.6 1.8 105.6 0.4 18.0

12 2.0 5.0 7.6 110.8 0.2 28.4 0.0 8.6 1.0 106.6 3.0 21.0

13 0.0 5.0 0.0 110.8 10.8 39.2 0.0 8.6 0.0 106.6 1.2 22.2

14 0.0 5.0 0.2 111.0 2.4 41.6 0.2 8.8 0.0 106.6 0.0 22.2

15 0.0 5.0 6.0 117.0 0.0 41.6 0.0 8.8 0.0 106.6 0.1 22.3

16 0.0 5.0 12.4 129.4 1.8 43.4 0.0 8.8 4.2 110.8 0.4 22.7

17 2.5 7.5 46.0 175.4 9.0 52.4 0.0 8.8 6.0 116.8 0.0 22.7

18 0.0 7.5 6.6 182.0 4.2 56.6 0.0 8.8 0.2 117.0 13.8 36.5

19 0.0 7.5 17.2 199.2 2.2 58.8 0.0 8.8 11.2 128.2 11.0 47.5

20 0.0 7.5 10.6 209.8 0.6 59.4 0.8 9.6 0.0 128.2 1.8 49.3

21 0.0 7.5 0.0 209.8 0.0 59.4 3.2 12.8 0.0 128.2 0.0 49.3

22 1.0 8.5 10.4 220.2 16.0 75.4 0.0 12.8 0.0 128.2 1.4 50.7

23 1.0 9.5 10.8 231.0 5.6 81.0 5.2 18.0 0.0 128.2 0.2 50.9

24 1.5 11.0 5.2 236.2 1.0 82.0 11.6 29.6 0.0 128.2 3.4 54.3

25 0.0 11.0 2.6 238.8 17.4 99.4 0.2 29.8 0.4 128.6 9.2 63.5

26 0.0 11.0 2.4 241.2 1.4 100.8 0.2 30.0 0.0 128.6 1.4 64.9

27 1.5 12.5 25.0 266.2 13.4 114.2 5.8 35.8 0.0 128.6 0.2 65.1

28 0.0 12.5 0.0 266.2 0.0 114.2 5.6 41.4 0.0 128.6 1.0 66.1

29 0.0 12.5 0.0 114.2 0.0 41.4 0.0 128.6 0.0 66.1

30 0.0 12.5 0.0 114.2 0.0 41.4 0.0 128.6 5.2 71.3

31 0.0 12.5 0.0 114.2 0.0 128.6

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 7.1 235.6 76.6 41.0 131.2 61.5




Date


1 2.8 2.8 0.6 0.6 2.2 2.2 0.0 0.0 2.0 2.0 0.0 0.0

2 7.0 9.8 0.0 0.6 50.4 52.6 0.4 0.4 0.4 2.4 0.6 0.6

3 7.4 17.2 0.0 0.6 25.8 78.4 1.0 1.4 0.0 2.4 0.4 1.0

4 0.0 17.2 0.0 0.6 0.0 78.4 1.4 2.8 3.6 6.0 0.2 1.2

5 1.0 18.2 0.0 0.6 4.2 82.6 0.4 3.2 13.6 19.6 47.6 48.8

6 0.0 18.2 0.0 0.6 9.8 92.4 10.8 14.0 0.4 20.0 11.8 60.6

7 0.0 18.2 0 0.6 0 92.4 5.8 19.8 4 24.0 19 79.6

8 0.0 18.2 0 0.6 0.2 92.6 15.4 35.2 2.6 26.6 5 84.6

9 0.0 18.2 1.2 1.8 0 92.6 8.8 44.0 2.4 29.0 24.4 109.0

10 0.0 18.2 0.0 1.8 0.0 92.6 0.8 44.8 10.6 39.6 15.0 124.0

11 0.0 18.2 1.4 3.2 13.2 105.8 0.2 45.0 23.2 62.8 3.2 127.2

12 10.4 28.6 0.0 3.2 4.8 110.6 0.0 45.0 5.6 68.4 0.2 127.4

13 1.6 30.2 0.0 3.2 13.6 124.2 0.0 45.0 0.6 69.0 0.0 127.4

14 2.0 32.2 2.2 5.4 6.2 130.4 14.0 59.0 5.6 74.6 0.0 127.4

15 5.6 37.8 0.4 5.8 23.8 154.2 6.0 65.0 7.6 82.2 0.0 127.4

16 1.0 38.8 1.2 7.0 44.6 198.8 12.4 77.4 3.8 86.0 0.0 127.4

17 0.0 38.8 7.4 14.4 0.0 198.8 0.2 77.6 26.8 112.8 0.2 127.6

18 0.0 38.8 0.0 14.4 0.0 198.8 0.0 77.6 8.0 120.8 8.0 135.6

19 0.0 38.8 0.4 14.8 0.0 198.8 0.0 77.6 3.2 124.0 0.0 135.6

20 0.0 38.8 7.8 22.6 0.0 198.8 0.0 77.6 6.6 130.6 0.0 135.6

21 0.0 38.8 22.8 45.4 0.0 198.8 0.0 77.6 0.0 130.6 0.0 135.6

22 0.0 38.8 0.0 45.4 0.0 198.8 0.2 77.8 0.0 130.6 3.4 139.0

23 25.4 64.2 2.6 48.0 0.0 198.8 0.0 77.8 13.4 144.0 10.2 149.2

24 4.2 68.4 0.0 48.0 0.0 198.8 0.0 77.8 0.0 144.0 11.8 161.0

25 3.8 72.2 3.0 51.0 0.0 198.8 0.0 77.8 0.6 144.6 15.4 176.4

26 7.4 79.6 3.2 54.2 0.0 198.8 0.0 77.8 0.0 144.6 3.0 179.4

27 6.2 85.8 1.0 55.2 0.0 198.8 0.0 77.8 0.0 144.6 13.2 192.6

28 0.0 85.8 3.6 58.8 6.6 205.4 0.0 77.8 6.8 151.4 0.2 192.8

29 20.6 106.4 1.2 60.0 0.0 205.4 1.6 79.4 0.4 151.8 6.0 198.8

30 3.2 109.6 1.4 61.4 4.8 210.2 0.2 79.6 0.0 151.8 26.8 225.6

31 20.4 130.0 15.8 77.2 0.4 80.0 8.4 234.0

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 101.6 47.1 114.2 37.9 84.8 130.0





200


Date


1 19.6 19.6 1.0 1.0 11.4 11.4 1.0 1.0 0.0 0.0 4.8 4.8

2 15.8 35.4 0.4 1.4 43.2 54.6 17.0 18.0 0.0 0.0 20.4 25.2

3 1.0 36.4 0.2 1.6 12.8 67.4 8.8 26.8 0.0 0.0 0.2 25.4

4 8.4 44.8 0.2 1.8 8.6 76.0 4.8 31.6 0.8 0.8 0.0 25.4

5 0.2 45.0 0.8 2.6 2.2 78.2 0.8 32.4 15.6 16.4 3.4 28.8

6 13.4 58.4 10.4 13.0 21.0 99.2 0.0 32.4 6.0 22.4 10.6 39.4

7 14.8 73.2 4.8 17.8 2.2 101.4 8.2 40.6 14.0 36.4 1.4 40.8

8 26.6 99.8 2.6 20.4 0.0 101.4 9.0 49.6 0.0 36.4 19.4 60.2

9 0.0 99.8 4.6 25.0 3.0 104.4 0.6 50.2 0.0 36.4 10.6 70.8

10 0.0 99.8 15.6 40.6 22.2 126.6 0.2 50.4 0.6 37.0 11.2 82.0

11 6.0 105.8 31.2 71.8 0.0 126.6 0.2 50.6 0.6 37.6 1.4 83.4

12 1.4 107.2 0.0 71.8 3.2 129.8 0.0 50.6 0.0 37.6 2.2 85.6

13 25.2 132.4 0.2 72.0 0.0 129.8 0.2 50.8 0.0 37.6 0.6 86.2

14 6.0 138.4 5.4 77.4 0.0 129.8 1.2 52.0 0.0 37.6 0.8 87.0

15 15.2 153.6 3.6 81.0 0.0 129.8 0.0 52.0 0.0 37.6 0.0 87.0

16 6.8 160.4 0.6 81.6 1.0 130.8 3.2 55.2 0.0 37.6 0.0 87.0

17 6.0 166.4 0.6 82.2 0.2 131.0 0.0 55.2 0.0 37.6 0.6 87.6

18 0.6 167.0 1.2 83.4 0.0 131.0 0.0 55.2 0.0 37.6 1.0 88.6

19 0.2 167.2 1.0 84.4 0.0 131.0 4.2 59.4 0.0 37.6 0.0 88.6

20 2.0 169.2 1.6 86.0 0.0 131.0 0.6 60.0 0.0 37.6 2.2 90.8

21 6.8 176.0 12.0 98.0 0.0 131.0 16.4 76.4 0.0 37.6 1.4 92.2

22 4.4 180.4 4.6 102.6 0.0 131.0 21.2 97.6 0.4 38.0 41.4 133.6

23 0.4 180.8 0.0 102.6 19.2 150.2 1.6 99.2 0.0 38.0 55.4 189.0

24 0.0 180.8 0.0 102.6 2.6 152.8 4.4 103.6 3.8 41.8 8.2 197.2

25 0.0 180.8 2.8 105.4 31.2 184.0 2.4 106.0 1.6 43.4 7.4 204.6

26 0.2 181.0 0.0 105.4 2.2 186.2 7.8 113.8 0.4 43.8 6.2 210.8

27 0.2 181.2 3.2 108.6 0.8 187.0 0.0 113.8 2.4 46.2 0.2 211.0

28 0.0 181.2 11.2 119.8 0.0 187.0 0.0 113.8 11.8 58.0 1.8 212.8

29 0.0 181.2 10.6 197.6 0.2 114.0 0.2 58.2 0.0 212.8

30 0.0 181.2 0.4 198.0 0.0 114.0 4.0 62.2 0.4 213.2

31 0.6 181.8 0.0 198.0 0.0 62.2

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 103.3 106.0 132.9 112.9 63.5 183.8



Date


1 0.0 0.0 0.0 0.0 15.4 15.4 0.0 0.0 2.0 2.0 1.0 1.0

2 0.0 0.0 64.6 64.6 0.0 15.4 0.0 0.0 15.8 17.8 0.4 1.4

3 0.0 0.0 30.0 94.6 0.0 15.4 0.0 0.0 2.0 19.8 2.4 3.8

4 0.4 0.4 0.6 95.2 0.0 15.4 0.4 0.4 3.0 22.8 1.0 4.8

5 0.2 0.6 19.2 114.4 1.0 16.4 0.2 0.6 3.4 26.2 0.0 4.8

6 0.0 0.6 10.0 124.4 2.0 18.4 0.0 0.6 1.2 27.4 0.8 5.6

7 0.6 1.2 2.4 126.8 40.2 58.6 0 0.6 8 35.4 17.4 23.0

8 17.2 18.4 0.6 127.4 27.6 86.2 0.4 1.0 14.6 50.0 6.6 29.6

9 0.0 18.4 0 127.4 27 113.2 26 27.0 8.2 58.2 0.0 29.6

10 9.8 28.2 0.2 127.6 11.4 124.6 3.6 30.6 0.0 58.2 11.0 40.6

11 9.2 37.4 0.2 127.8 9.2 133.8 6.4 37.0 21.4 79.6 11.2 51.8

12 11.2 48.6 2.2 130.0 10.6 144.4 11.0 48.0 27.4 107.0 6.6 58.4

13 2.0 50.6 10.0 140.0 0.0 144.4 11.6 59.6 1.4 108.4 19.0 77.4

14 3.4 54.0 1.0 141.0 0.6 145.0 4.6 64.2 0.0 108.4 8.0 85.4

15 0.2 54.2 0.0 141.0 5.2 150.2 7.0 71.2 0.0 108.4 0.0 85.4

16 4.8 59.0 33.2 174.2 0.0 150.2 30.2 101.4 0.4 108.8 1.0 86.4

17 2.8 61.8 0.6 174.8 12.4 162.6 8.4 109.8 0.2 109.0 3.4 89.8

18 0.6 62.4 0.0 174.8 0.0 162.6 4.6 114.4 0.2 109.2 20.4 110.2

19 14.4 76.8 1.6 176.4 0.0 162.6 1.6 116.0 0.6 109.8 0.0 110.2

20 17.4 94.2 27.0 203.4 0.0 162.6 48.2 164.2 1.4 111.2 0.0 110.2

21 1.2 95.4 4.2 207.6 0.0 162.6 3.8 168.0 10.8 122.0 5.0 115.2

22 23.2 118.6 0.4 208.0 0.0 162.6 6.6 174.6 7.0 129.0 8.8 124.0

23 0.0 118.6 8.8 216.8 0.0 162.6 6.2 180.8 15.0 144.0 0.8 124.8

24 0.0 118.6 0.0 216.8 0.0 162.6 35.4 216.2 0.1 144.1 24.2 149.0

25 0.0 118.6 2.4 219.2 0.0 162.6 6.0 222.2 n/a 144.1 3.6 152.6

26 18.8 137.4 0.0 219.2 0.0 162.6 27.0 249.2 21.8 165.9 14.8 167.4

27 2.6 140.0 0.0 219.2 0.0 162.6 5.8 255.0 n/a 165.9 15.6 183.0

28 7.2 147.2 0.0 219.2 0.0 162.6 6.2 261.2 n/a 165.9 5.2 188.2

29 4.0 151.2 0.0 219.2 0.6 163.2 9.2 270.4 34.8 200.7 6.0 194.2

30 2.6 153.8 0.0 219.2 5.6 168.8 4.0 274.4 0.8 201.5 0.2 194.4

31 0.0 153.8 1.2 220.4 0.0 274.4 0.4 194.8

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 120.2 134.4 91.7 130.0 112.6 108.2




201


Date


1 11.4 11.4 0.6 0.6 9.2 9.2 0.0 0.0 0.0 0.0 0.4 0.4

2 8.4 19.8 3.6 4.2 19.2 28.4 0.8 0.8 0.0 0.0 12.6 13.0

3 17.8 37.6 1.0 5.2 15.8 44.2 0.6 1.4 0.0 0.0 7.4 20.4

4 9.0 46.6 1.8 7.0 6.8 51.0 5.6 7.0 0.0 0.0 4.0 24.4

5 39.6 86.2 0.8 7.8 0.0 51.0 20.2 27.2 0.8 0.8 0.6 25.0

6 14.0 100.2 0.6 8.4 5.2 56.2 2.0 29.2 0.2 1.0 0.8 25.8

7 11 111.2 0 8.4 1.6 57.8 1 30.2 24 25.0 2 27.8

8 0.0 111.2 0.6 9.0 0.0 57.8 0.6 30.8 14 39.0 0.2 28.0

9 0.0 111.2 1 10.0 0.0 57.8 6.4 37.2 9.8 48.8 0 28.0

10 0.0 111.2 0.4 10.4 0.0 57.8 0.2 37.4 18.6 67.4 0.0 28.0

11 10.2 121.4 0.4 10.8 2.8 60.6 22.6 60.0 6.4 73.8 3.2 31.2

12 13.6 135.0 1.6 12.4 0.0 60.6 3.8 63.8 7.0 80.8 2.2 33.4

13 13.2 148.2 8.2 20.6 0.6 61.2 1.6 65.4 3.2 84.0 3.6 37.0

14 9.0 157.2 1.0 21.6 0.0 61.2 8.8 74.2 0.0 84.0 0.2 37.2

15 16.0 173.2 1.8 23.4 5.0 66.2 1.2 75.4 0.0 84.0 0.0 37.2

16 0.0 173.2 0.4 23.8 0.0 66.2 0.0 75.4 0.0 84.0 4.0 41.2

17 4.4 177.6 6.2 30.0 4.2 70.4 0.4 75.8 0.0 84.0 0.0 41.2

18 26.2 203.8 17.2 47.2 0.0 70.4 0.8 76.6 0.0 84.0 1.2 42.4

19 4.8 208.6 0.0 47.2 0.0 70.4 0.4 77.0 0.0 84.0 45.6 88.0

20 2.8 211.4 1.8 49.0 16.8 87.2 16.8 93.8 7.4 91.4 0.0 88.0

21 0.6 212.0 6.4 55.4 2.0 89.2 21.2 115.0 0.8 92.2 0.8 88.8

22 0.0 212.0 0.0 55.4 8.8 98.0 1.4 116.4 1.2 93.4 0.6 89.4

23 12.6 224.6 2.6 58.0 0.2 98.2 0.0 116.4 18.8 112.2 0.0 89.4

24 14.6 239.2 0.4 58.4 2.6 100.8 0.0 116.4 1.2 113.4 0.0 89.4

25 3.8 243.0 4.4 62.8 0.0 100.8 0.0 116.4 11.0 124.4 0.0 89.4

26 3.8 246.8 2.0 64.8 7.4 108.2 0.0 116.4 0.0 124.4 26.4 115.8

27 4.8 251.6 0.0 64.8 0.0 108.2 0.0 116.4 3.8 128.2 5.6 121.4

28 1.0 252.6 10.8 75.6 49.4 157.6 0.0 116.4 14.6 142.8 2.6 124.0

29 0.8 253.4 3.6 161.2 0.0 116.4 0.0 142.8 0.2 124.2

30 0.8 254.2 1.2 162.4 0.0 116.4 0.0 142.8 1.0 125.2

31 0.2 254.4 0.2 162.6 0.0 142.8

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 144.5 66.9 109.1 115.2 145.7 107.9




Date


1 1.0 1.0 0.0 0.0 0.0 0.0 17.6 17.6 18.6 18.6 5.0 5.0

2 4.0 5.0 0.4 0.4 0.2 0.2 9.4 27.0 5.0 23.6 29.8 34.8

3 1.0 6.0 0.0 0.4 0.0 0.2 0.4 27.4 4.6 28.2 5.2 40.0

4 0.2 6.2 0.2 0.6 0.0 0.2 0.4 27.8 74.8 103.0 2.4 42.4

5 0.0 6.2 0.8 1.4 0.0 0.2 0.0 27.8 31.6 134.6 40.0 82.4

6 0.0 6.2 14.8 16.2 24.8 25.0 19.4 47.2 0.0 134.6 18.4 100.8

7 0 6.2 0.6 16.8 0.4 25.4 8.8 56.0 9.4 144.0 13.8 114.6

8 0.4 6.6 0 16.8 25 50.4 2.8 58.8 0.2 144.2 8 122.6

9 3 9.6 0 16.8 0 50.4 3 61.8 0.2 144.4 1.4 124.0

10 0.4 10.0 0.0 16.8 1.0 51.4 4.8 66.6 0.2 144.6 14.2 138.2

11 0 10 0.0 16.8 7.2 58.6 0.1 66.7 0.0 144.6 9.0 147.2

12 0.0 10.0 11.4 28.2 3.2 61.8 0.0 66.7 0.0 144.6 5.0 152.2

13 13.4 23.4 6.8 35.0 0.6 62.4 0.0 66.7 0.0 144.6 1.0 153.2

14 0.0 23.4 8.4 43.4 0.2 62.6 0.0 66.7 0.2 144.8 2.4 155.6

15 7.4 30.8 1.4 44.8 n/a 62.6 0.0 66.7 8.0 152.8 0.2 155.8

16 4.6 35.4 1.4 46.2 n/a 62.6 0.0 66.7 0.0 152.8 30.2 186.0

17 9.6 45.0 7.4 53.6 n/a 62.6 0.0 66.7 0.2 153.0 0.0 186.0

18 14.2 59.2 9.6 63.2 n/a 62.6 0.0 66.7 0.0 153.0 0.0 186.0

19 31.0 90.2 0.0 63.2 n/a 62.6 0.0 66.7 0.4 153.4 0.0 186.0

20 3.0 93.2 0.0 63.2 n/a 62.6 0.0 66.7 0.0 153.4 18.6 204.6

21 3.4 96.6 0.0 63.2 n/a 62.6 3.8 70.5 1.4 154.8 0.2 204.8

22 0.2 96.8 0.0 63.2 n/a 62.6 5.0 75.5 0.8 155.6 19.0 223.8

23 0.0 96.8 0.0 63.2 n/a 62.6 6.6 82.1 12.4 168.0 17.8 241.6

24 1.4 98.2 0.0 63.2 n/a 62.6 5.0 87.1 8.8 176.8 17.4 259.0

25 0.0 98.2 2.4 65.6 n/a 62.6 0.8 87.9 4.8 181.6 5.0 264.0

26 0.0 98.2 2.4 68.0 n/a 62.6 0.0 87.9 3.8 185.4 4.6 268.6

27 0.0 98.2 0.0 68.0 n/a 62.6 6.6 94.5 13.8 199.2 2.0 270.6

28 0.0 98.2 0.0 68.0 n/a 62.6 0.0 94.5 20.8 220.0 0.0 270.6

29 0.0 98.2 4.2 72.2 n/a 62.6 3.0 97.5 7.6 227.6 16.8 287.4

30 0.0 98.2 2.0 74.2 n/a 62.6 8.6 106.1 3.0 230.6 4.8 292.2

31 0.0 98.2 0.0 74.2 14.8 120.9 10.2 302.4

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 76.7 45.2 34.0 57.3 128.8 168.0


August September DecemberNovemberOctoberJuly



202

DAILY AND CUMULATIVE RAINFALL AT ENNERDALE IN mm FOR 2000

Date


1 0.6 0.6 7.4 7.4 15.4 15.4 1.6 1.6 0 0.0 16.2 16.2

2 16.6 17.2 1.2 8.6 24.6 40.0 3.6 5.2 0.2 0.2 6.2 22.4

3 0.6 17.8 19.2 27.8 0.0 40.0 0.2 5.4 0 0.2 23.4 45.8

4 15.0 32.8 4.8 32.6 0.2 40.2 0.0 5.4 0 0.2 6.0 51.8

5 9.4 42.2 8.0 40.6 8.6 48.8 0.0 5.4 0 0.2 6.8 58.6

6 4.2 46.4 6.6 47.2 6.4 55.2 0.0 5.4 0 0.2 3.0 61.6

7 16.2 62.6 20.8 68.0 11.4 66.6 1.6 7.0 0 0.2 1.6 63.2

8 0.0 62.6 6.2 74.2 5.0 71.6 0.2 7.2 0 0.2 1.6 64.8

9 0.0 62.6 16.4 90.6 3.0 74.6 0.0 7.2 0 0.2 14.2 79.0

10 13.4 76.0 0.2 90.8 3.8 78.4 16.0 23.2 0 0.2 5.2 84.2

11 45.4 121.4 6.0 96.8 0.0 78.4 5.2 28.4 0 0.2 0.4 84.6

12 14.4 135.8 0.0 96.8 0.2 78.6 7.8 36.2 0 0.2 3.2 87.8

13 0.6 136.4 3.0 99.8 1.2 79.8 6.6 42.8 0 0.2 1.4 89.2

14 0.0 136.4 2.6 102.4 0.4 80.2 0.0 42.8 0 0.2 0.0 89.2

15 0.0 136.4 14.8 117.2 0.4 80.6 0.6 43.4 0.2 0.4 0.0 89.2

16 0.2 136.6 0.8 118.0 0.0 80.6 2.8 46.2 18.4 18.8 0.0 89.2

17 0.4 137.0 9.4 127.4 0.0 80.6 3.2 49.4 14.4 33.2 0.0 89.2

18 0.0 137.0 1.0 128.4 0.0 80.6 0.8 50.2 6.8 40.0 0.0 89.2

19 0.4 137.4 0.0 128.4 0.0 80.6 12.4 62.6 0.4 40.4 1.2 90.4

20 0.0 137.4 13.4 141.8 0.0 80.6 7.2 69.8 4.2 44.6 12.4 102.8

21 1.6 139.0 0.4 142.2 0.0 80.6 11.6 81.4 0.4 45.0 11.4 114.2

22 0.2 139.2 2.4 144.6 0.0 80.6 0.0 81.4 4.6 49.6 1.6 115.8

23 1.2 140.4 10.0 154.6 0.0 80.6 2.2 83.6 12.2 61.8 5.8 121.6

24 0.0 140.4 2.2 156.8 2.0 82.6 2.4 86.0 1.2 63.0 0.4 122.0

25 0.0 140.4 0.0 156.8 0.0 82.6 3.4 89.4 0.8 63.8 0.0 122.0

26 1.4 141.8 23.6 180.4 0.2 82.8 7.4 96.8 5.0 68.8 0.0 122.0

27 3.6 145.4 15.2 195.6 0.4 83.2 0.0 96.8 0.6 69.4 0.0 122.0

28 25.0 170.4 6.2 201.8 0.0 83.2 0.4 97.2 0.6 70.0 0.2 122.2

29 2.6 173.0 1.6 203.4 0.0 83.2 1.6 98.8 0 70.0 0.6 122.8

30 16.8 189.8 0.0 83.2 0.0 98.8 0 70.0 0 122.8

31 40.0 229.8 0.4 83.6 10.0 80.0

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 130.6 180.0 56.1 97.8 81.6 105.9



Date


1 0.2 0.2 22.6 22.6 3.2 3.2 16.0 16.0 13.2 13.2 30.6 30.6

2 12.6 12.8 3.0 25.6 0.0 3.2 3.2 19.2 6.8 20.0 5.6 36.2

3 0.0 12.8 0.4 26.0 0.0 3.2 13.4 32.6 2.8 22.8 21.2 57.4

4 0.0 12.8 0.2 26.2 38.0 41.2 31.6 64.2 0.0 22.8 13.6 71.0

5 2.2 15.0 0.6 26.8 12.0 53.2 0.6 64.8 18.2 41.0 15.4 86.4

6 5.6 20.6 0.4 27.2 12.4 65.6 11.2 76.0 19.0 60.0 3.4 89.8

7 1.2 21.8 2.2 29.4 11.4 77.0 16.2 92.2 10.8 70.8 13.2 103.0

8 28.4 50.2 3.6 33.0 0.2 77.2 9.6 101.8 12.6 83.4 29.0 132.0

9 18.8 69.0 29.4 62.4 3.0 80.2 34.6 136.4 0.0 83.4 10.2 142.2

10 0.6 69.6 0.0 62.4 2.0 82.2 28.2 164.6 13.0 96.4 8.0 150.2

11 0.0 69.6 0.6 63.0 1.4 83.6 1.6 166.2 26.0 122.4 39.0 189.2

12 1.8 71.4 34.8 97.8 0.0 83.6 3.0 169.2 9.4 131.8 20.2 209.4

13 1.8 73.2 41.4 139.2 5.6 89.2 19.0 188.2 4.2 136.0 3.4 212.8

14 0.0 73.2 0.0 139.2 0.6 89.8 0.2 188.4 0.2 136.2 1.2 214.0

15 0.0 73.2 0.0 139.2 1.4 91.2 0.0 188.4 23.6 159.8 0.0 214.0

16 0.0 73.2 0.0 139.2 1.4 92.6 5.4 193.8 12.2 172.0 1.6 215.6

17 0.0 73.2 0.0 139.2 20.6 113.2 20.4 214.2 0.8 172.8 0.2 215.8

18 0.0 73.2 0.0 139.2 0.8 114.0 3.8 218.0 12.2 185.0 0.0 215.8

19 0.0 73.2 0.0 139.2 14.6 128.6 3.0 221.0 1.6 186.6 11.8 227.6

20 0.0 73.2 0.0 139.2 6.4 135.0 3.8 224.8 1.2 187.8 0.0 227.6

21 0.0 73.2 3.0 142.2 10.6 145.6 0.0 224.8 0.6 188.4 0.0 227.6

22 0.0 73.2 0.0 142.2 2.2 147.8 6.2 231.0 1.4 189.8 0.2 227.8

23 0.0 73.2 0.0 142.2 0.0 147.8 6.8 237.8 3.6 193.4 1.4 229.2

24 0.0 73.2 0.0 142.2 31.0 178.8 55.4 293.2 16.2 209.6 0.0 229.2

25 0.0 73.2 10.6 152.8 0.0 178.8 3.0 296.2 31.6 241.2 0.0 229.2

26 0.0 73.2 1.0 153.8 27.6 206.4 20.2 316.4 3.8 245.0 0.0 229.2

27 0.4 73.6 2.2 156.0 38.8 245.2 1.6 318.0 24.8 269.8 0.0 229.2

28 0.0 73.6 0.2 156.2 0.8 246.0 12.0 330.0 32.8 302.6 1.6 230.8

29 0.0 73.6 0.0 156.2 1.4 247.4 11.2 341.2 3.2 305.8 0.0 230.8

30 3.0 76.6 1.4 157.6 0.6 248.0 5.8 347.0 17.4 323.2 0.6 231.4

31 20.2 96.8 32.4 190.0 13.2 360.2 27.6 259.0

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 75.6 115.9 134.8 170.7 180.6 143.9




203


Date


1 7.8 7.8 3.8 3.8 2.6 2.6 1.8 1.8 0.2 0.2 11.2 11.2

2 4.2 12.0 12.8 16.6 0.2 2.8 6.8 8.6 0.0 0.2 1.0 12.2

3 26.4 38.4 1.6 18.2 0.0 2.8 3.8 12.4 0.0 0.2 0.0 12.2

4 0.0 38.4 4.8 23.0 0.0 2.8 0.8 13.2 0.0 0.2 0.2 12.4

5 2.6 41.0 13.6 36.6 0.0 2.8 10.8 24.0 0.0 0.2 2.6 15.0

6 6.4 47.4 7.6 44.2 13.6 16.4 24.6 48.6 0.0 0.2 18.2 33.2

7 5.4 52.8 0.0 44.2 0.0 16.4 2.2 50.8 0.0 0.2 0.0 33.2

8 0.0 52.8 0.0 44.2 10.4 26.8 0.2 51.0 0.0 0.2 7.4 40.6

9 0.0 52.8 7.6 51.8 8.6 35.4 8.4 59.4 0 0.2 1.2 41.8

10 0.2 53.0 17.4 69.2 2.2 37.6 0.8 60.2 0 0.2 1.0 42.8

11 0.0 53.0 0.0 69.2 8.6 46.2 0.0 60.2 0 0.2 0.0 42.8

12 0.0 53.0 0.2 69.4 0.2 46.4 0.4 60.6 0 0.2 0.0 42.8

13 0.0 53.0 0.0 69.4 0.0 46.4 0.8 61.4 1 1.6 0.0 42.8

14 0.0 53.0 0.0 69.4 0.0 46.4 1.2 62.6 3 5.0 4.4 47.2

15 0.0 53.0 0.0 69.4 0.0 46.4 0.2 62.8 14.6 19.6 5.8 53.0

16 0.0 53.0 0.2 69.6 0.0 46.4 0.6 63.4 3.6 23.2 0.0 53.0

17 0.0 53.0 0.0 69.6 0.0 46.4 4.6 68.0 7.0 30.2 0.0 53.0

18 0.4 53.4 1.6 71.2 0.0 46.4 0.8 68.8 0.0 30.2 6.4 59.4

19 0.2 53.6 0.0 71.2 0.0 46.4 1.4 70.2 0.2 30.4 15.0 74.4

20 0.4 54.0 1.8 73.0 0.0 46.4 0.0 70.2 0.0 30.4 0.0 74.4

21 0.8 54.8 0.2 73.2 4.6 51.0 18.2 88.4 0.0 30.4 0.0 74.4

22 8.4 63.2 0.8 74.0 1.0 52.0 9.4 97.8 0.0 30.4 0.0 74.4

23 13.6 76.8 0.0 74.0 0.6 52.6 0.0 97.8 0.0 30.4 0.0 74.4

24 5.0 81.8 0.0 74.0 0.0 52.6 3.6 101.4 0.0 30.4 0.0 74.4

25 12.0 93.8 11.0 85.0 0.0 52.6 3.4 104.8 6.8 37.2 2.6 77.0

26 3.6 97.4 9.0 94.0 0.2 52.8 0.8 105.6 6.6 43.8 8.4 85.4

27 0.0 97.4 6.6 100.6 4.0 56.8 12.4 118.0 3.8 47.6 3.2 88.6

28 0.4 97.8 3.0 103.6 0.0 56.8 8.2 126.2 1.6 49.2 8.0 96.6

29 0.4 98.2 0.6 57.4 9.6 135.8 0 49.4 2.2 98.8

30 4.2 102.4 19.2 76.6 0.2 136.0 5 54.6 0 99.0

31 0.0 102.4 0.8 77.4 1.4 56.0

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 58.2 91.7 51.9 134.7 57.1 85.3



Date


1 0.0 0.0 0.8 0.8 6.4 6.4 0.2 0.2 0.4 0.4 0.8 0.8

2 0.2 0.2 1.2 2.0 1.4 7.8 3.4 3.6 4.0 4.4 0.0 0.8

3 32.0 32.2 1.2 3.2 2.0 9.8 3.8 7.4 0.4 4.8 20.6 21.4

4 0.0 32.2 0.0 3.2 1.4 11.2 21.4 28.8 1.8 6.6 6.0 27.4

5 0.0 32.2 1.4 4.6 6.6 17.8 25.4 54.2 16.2 22.8 7.0 34.4

6 1.4 33.6 0.6 5.2 0.6 18.4 17.8 72.0 7.4 30.2 9.0 43.4

7 2.2 35.8 12.8 18.0 2.8 21.2 34.0 106.0 9.2 39.4 7.2 50.6

8 2.8 38.6 1.4 19.4 0.2 21.4 16.6 122.6 0.4 39.8 0.0 50.6

9 13.8 52.4 0.0 19.4 0.0 21.4 10.0 132.6 1.6 41.4 0.0 50.6

10 12.2 64.6 11.4 30.8 0.0 21.4 3.0 135.6 1.2 42.6 0.2 50.8

11 0.8 65.4 13.4 44.2 0.0 21.4 25.6 161.2 9.8 52.4 0.0 50.8

12 1.4 66.8 14.2 58.4 29.4 50.8 3.8 165.0 0.4 52.8 0.0 50.8

13 2.8 69.6 1.4 59.8 8.0 58.8 7.4 172.4 2.0 54.8 0.0 50.8

14 4.6 74.2 0.2 60.0 5.2 64.0 20.4 192.8 0.0 54.8 0.0 50.8

15 0.0 74.2 10.2 70.2 1.6 65.6 7.0 199.8 0.0 54.8 0.2 51.0

16 0.0 74.2 1.4 71.6 0.4 66.0 0.0 199.8 0.0 54.8 0.0 51.0

17 0.0 74.2 0.8 72.4 0.0 66.0 14.8 214.6 0.0 54.8 0.4 51.4

18 0.0 74.2 8.8 81.2 0.0 66.0 0.2 214.8 0.4 55.2 0.2 51.6

19 0.0 74.2 15.6 96.8 4.0 70.0 4.2 219.0 0.0 55.2 0.0 51.6

20 2.8 77.0 0.0 96.8 0.2 70.2 5.0 224.0 1.4 56.6 3.4 55.0

21 1.2 78.2 6.8 103.6 0.0 70.2 18.8 242.8 11.8 68.4 2.8 57.8

22 0.2 78.4 0.0 103.6 0.0 70.2 2.0 244.8 0.0 68.4 0.0 57.8

23 2.2 80.6 0.4 104.0 0.0 70.2 12.8 257.6 2.8 71.2 8.6 66.4

24 0.8 81.4 0.8 104.8 0.0 70.2 13.4 271.0 10.2 81.4 3.2 69.6

25 0.0 81.4 5.6 110.4 1.2 71.4 11.4 282.4 1.8 83.2 0.0 69.6

26 0.0 81.4 0.0 110.4 6.8 78.2 21.2 303.6 3.8 87.0 5.8 75.4

27 0.0 81.4 0.0 110.4 32.0 110.2 0.2 303.8 11.4 98.4 1.8 77.2

28 0.0 81.4 0.0 110.4 12.4 122.6 0.0 303.8 42.8 141.2 0.2 77.4

29 0.0 81.4 8.4 118.8 3.0 125.6 0.0 303.8 8.0 149.2 0.0 77.4

30 7.2 88.6 0.2 119.0 23.4 149.0 1.8 305.6 16.4 165.6 0.0 77.4

31 0.0 88.6 0.6 119.6 0.2 305.8 0.0 77.4

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 69.2 72.9 81.0 144.9 92.5 43.0




204


Date


1 0.2 0.2 5.8 5.8 1.0 1.0 21.8 21.8 0.8 0.8 1.6 1.6

2 0.2 0.4 8.8 14.6 0.6 1.6 1.6 23.4 0.4 1.2 14.4 16.0

3 0.0 0.4 4.0 18.6 0.0 1.6 0.6 24.0 0.0 1.2 10.4 26.4

4 2.8 3.2 17.4 36.0 0.2 1.8 0.0 24.0 2.6 3.8 0.2 26.6

5 0.0 3.2 5.0 41.0 13.4 15.2 0.0 24.0 0.0 3.8 0.4 27.0

6 1.0 4.2 14.6 55.6 1.4 16.6 0.0 24.0 0.0 3.8 0.0 27.0

7 0.0 4.2 24.6 80.2 0.0 16.6 0.0 24.0 4.2 8.0 0.0 27.0

8 0.0 4.2 10.0 90.2 6.4 23.0 0.0 24.0 0.0 8.0 12.6 39.6

9 0.0 4.2 4.6 94.8 26.6 49.6 0.0 24.0 0.0 8.0 26.2 65.8

10 0.2 4.4 31.0 125.8 0.8 50.4 0.0 24.0 0.0 8.0 9.4 75.2

11 10.2 14.6 0.6 126.4 0.0 50.4 0.4 24.4 0.0 8.0 11.2 86.4

12 10.4 25.0 1.0 127.4 0.0 50.4 0.0 24.4 1.6 9.6 4.0 90.4

13 13.8 38.8 0.0 127.4 0.0 50.4 0.6 25.0 15.4 25.0 10.6 101.0

14 10.4 49.2 0.0 127.4 0.0 50.4 4.2 29.2 6.6 31.6 26.2 127.2

15 0.0 49.2 0.0 127.4 3.4 53.8 0.0 29.2 0.6 32.2 6.4 133.6

16 43.8 93.0 0.0 127.4 2.0 55.8 0.0 29.2 0.0 32.2 7.6 141.2

17 1.2 94.2 3.2 130.6 1.4 57.2 0.8 30.0 9.8 42.0 0.0 141.2

18 0.4 94.6 2.6 133.2 0.0 57.2 1.8 31.8 6.8 48.8 0.0 141.2

19 3.2 97.8 25.0 158.2 4.8 62.0 0.4 32.2 44.2 93.0 0.0 141.2

20 1.8 99.6 4.0 162.2 8.8 70.8 28.0 60.2 14.4 107.4 2.6 143.8

21 18.0 117.6 29.6 191.8 0.2 71.0 24.8 85.0 11.2 118.6 7.6 151.4

22 17.8 135.4 3.2 195.0 0.0 71.0 0.0 85.0 11.6 130.2 0.8 152.2

23 14.4 149.8 2.6 197.6 0.0 71.0 0.0 85.0 15.8 146.0 0.0 152.2

24 0.2 150.0 9.4 207.0 17.8 88.8 0.8 85.8 21.0 167.0 1.6 153.8

25 26.0 176.0 42.4 249.4 1.2 90.0 28.2 114.0 9.2 176.2 1.6 155.4

26 0.0 176.0 0.8 250.2 0.0 90.0 6.2 120.2 17.4 193.6 2.0 157.4

27 2.4 178.4 13.6 263.8 0.0 90.0 7.0 127.2 0.0 193.6 0.0 157.4

28 11.8 190.2 5.6 269.4 0.0 90.0 10.4 137.6 11.6 205.2 0.0 157.4

29 11.6 201.8 0.0 90.0 5.6 143.2 1.6 206.8 1.4 158.8

30 0.4 202.2 20.0 110.0 3.2 146.4 3.0 209.8 34.2 193.0

31 35.2 237.4 19.0 129.0 0.0 209.8

LTA 176.0 113.0 149.0 101.0 98.0 116.0

1961-90

% LTA 134.9 238.4 86.6 145.0 214.1 166.4


N.B. Bold data from the Environment Agency Historical Records, not directly read by United Utilities



Date


1 18.4 18.4 3.2 3.2

2 0.4 18.8 14.8 18.0

3 1.8 20.6 0.0 18.0

4 11.6 32.2 0.2 18.2

5 0.0 32.2 0.0 18.2

6 0.8 33.0 0.0 18.2

7 13.4 46.4 5.0 23.2

8 0.0 46.4 0.0 23.2

9 1.8 48.2 2.2 25.4

10 2.4 50.6 0.6 26.0

11 4.0 54.6 4.0 30.0

12 0.0 54.6 14.2 44.2

13 0.0 54.6 9.2 53.4

14 0.2 54.8 7.6 61.0

15 0.0 54.8 0.0 61.0

16 0.0 54.8 0.0 61.0

17 0.0 54.8 13.0 74.0

18 15.8 70.6 8.2 82.2

19 8.4 79.0 0.0 82.2

20 2.2 81.2 0.0 82.2

21 2.0 83.2 0.0 82.2

22 19.4 102.6 0.0 82.2

23 3.0 105.6 7.0 89.2

24 2.4 108.0 0.6 89.8

25 1.8 109.8 0.0 89.8

26 0.0 109.8 0.0 89.8

27 0.2 110.0 0.0 89.8

28 8.2 118.2 11.4 101.2

29 0.0 118.2 1.8 103.0

30 3.6 121.8 15.4 118.4

31 3.6 125.4 0.0 118.4

LTA 128.0 164.0 184.0 211.0 179.0 180.0

1961-90

% LTA 98.0 72.2 0.0 0.0 0.0 0.0




Water Supply in Allerdale & Copeland - Events and incidents

205

H. Events or incidents.

Water companies are required by the WaterUndertakers (Information) Direction, initiallyissued in 1990 and amended and reissued in1992 and again in 1998, to notify theAuthorities of any event which, by reason ofits effect on the quality or sufficiency ofdrinking water, gives rise to, or is likely to giverise to, a significant risk to the health ofpersons to whom it is supplied. Notification issimilarly required for events that are ofnational significance, may give rise tosignificant publicity or cause significantconcern to consumers.

The Inspectorate assesses all such notifiedevents on behalf of the Authorities, carries outinvestigations as necessary and makes publicthe outcome of its investigations. During theperiod of the study, there were no majorincidents that so affected the quality ofdrinking water supplied in the study area thatformal notification to the Drinking WaterInspectorate resulted in an “incident” beingconfirmed and a report issued.

However, there were a small number of eventsin the study area that were discussed with thelocal authorities and the CCDC. These were;

1. Boil water notice issued on the 4th August1998 to Allerdale residents receiving waterfrom Cornhow WTW when Park Beckburst its banks following heavy rainfall.River water entered Crummock Lake andaffected the quality of the treated waterfrom Cornhow. The notice waswithdrawn on the 7th August 1998 andno excess of cases of cryptosporidiosiswere noted in the study area at this time.

2. Continuous monitoring analysis inaccordance with the CryptosporidiumRegulations (See sub section I on nextpage, The Water Supply (Water Quality)(Amendment) Regulations 1999)identified in June 2000, Cryptosporidiumoocysts greater than the treatmentstandard of less than 1 per 10 litres oftreated water in one sample; and anothersample with just less than the treatmentstandard along the Thirlmere aqueduct.Water from Thirlmere is used for drinkingwater production in the southeastern partof the Allerdale portion of the study area.Subsequent to this event, no excess ofcases of cryptosporidiosis were noted inthe study area.

In addition in April 1999, an excess ofCryptosporidium oocysts were detected inthe Thirlmere aqueduct. Cryptosporidiumcases were subsequently detected in theNorth West but no cases were detected inAllerdale. A boil water notice was notissued.

3. Cornhow WTW had to discontinuecontinuous membrane based microfiltration(CMF) of treated water between the 2ndand the 8th June 2001, due to a failure ofthe main raw water feed pump andbackup systems. In accordance with theCryptosporidium Regulations continuousmonitoring of the treated water wasimplemented until CMF couldre -commence. Monitoring results showedthat the highest oocyst levels were at 8%of the treatment standard. Subsequent tothis event, no excess of cases ofcryptosporidiosis were noted in the studyarea.


Water Supply in Allerdale & Copeland - Regulation of Water Supplies

206

I. Regulation of Water Supplies

Public drinking water regulations Public drinking water is any water suppliedfor drinking, washing, cooking or foodproduction by a water company appointedunder the Water Industry Act 1991(“the Act”)as a water undertaker. The Act requires awater company to supply only water that iswholesome at the time of supply, which iswhen water passes from the company’s pipeinto a consumer’s pipe.

“Wholesomeness” is defined by reference tostandards and other requirements set out inthe Water Supply (Water Quality)Regulations 1989, as amended [2]. Theseinclude an additional “catch all” requirementthat it does not contain any element,organism or substance whether alone or incombination, at a concentration or value thatwould be detrimental to public health.Drinking water is regarded as wholesomeprovided it meets these standards.

The Regulations incorporate all the standardsset out in the EC “Drinking Water Directive(80/778/EEC) [11]. In total, the 1989Regulations set numerical standards for 55parameters, of which 11 are nationalstandards additional to the 1980 Directiverequirements, and descriptive standards for afurther two. The national standards areinterpreted as either three or 12 monthlyaverages. In addition to these standardsapplying to water at the time of supply, anumber of standards apply to water issuingfrom treatment works and to water held inservice reservoirs within the distributionsystem.

The 1989 Regulations also require that waterreceive treatment appropriate to the quality ofthe raw source water, and regulates theapplication and introduction of substancesand products, and the use of processes.

Contravention of the parts of the 1989Regulations relating to the application ofsubstances and products, and use of processes,is an offence. Section 70 of “the Act” makes ita criminal offence for a water undertaker tosupply water that is unfit for humanconsumption. Water companies areresponsible for monitoring the quality ofwater supplies and their role is subject tochecks by local authorities and the DrinkingWater Inspectorate. Results of the qualitymonitoring must be made publicly availableon a register. The water companies must alsoproduce annually a report on the quality ofsupplies in the authorities’ area.

Finally, water companies are required tonotify the Authorities of any event which, byreason of its effect on the quality orsufficiency of drinking water, gives rise to, oris likely to give rise to, a significant risk to thehealth of persons to whom it is supplied.

The Water Supply (Water Quality)(Amendment) Regulations 1999The Government introduced the aboveRegulations, based on a treatment standardwith associated monitoring requirement from30 June 1999. These Regulations set atreatment standard of an average of less thanone oocyst in 10 litres of water supplied froma treatment works. As a treatment standard itdoes not take into account different species ofCryptosporidium, nor the viability of anyoocysts detected.

Monitoring is by continuous sampling of notless than an average volume of 40 litres perhour, with samples being taken daily foranalysis. The protocol on analysis of samplesissued with the Regulations sets out therequirements for laboratory facilities andanalytical method that must be used forcompliance testing. The analysis can only becarried out at laboratories approved by theDWI. Strict rules are set down for all aspects


Water Supply in Allerdale & Copeland - Regulation of Water Supplies

207

of the sampling and analysis to permit theresults to be used as evidence in a Court ofLaw.

The Regulations required water undertakersto carry out a risk assessment for each of theirwater treatment works by 30th September1999, to establish based upon guidance issuedby the DWI, whether there was a significantrisk from Cryptosporidium oocysts beingpresent at times in treated water. For worksidentified as at risk, the water companies musttreat the water to ensure that the standard ismet and also demonstrate compliance withthe standard by continuous monitoring andreporting of the daily results to the DWI.

Monitoring at the highest risk sites began onthe 1 April 2000 and, at other sites atsignificant risk, in accordance with aprogramme agreed with the Inspectorate.WTW works identified at significant risk andwithout physical treatment barriers capable ofremoving Cryptosporidium oocysts have beenmade the subject of an improvementprogramme to a timetable agreed between theDWI and the operating water company. Theprogramme may require that appropriatetreatment is provided or in some cases for thesource to be abandoned or changed.

As an alternative to continuous monitoring, awater company may install treatment plantcapable of continuously removing or retainingparticles greater than 1 µm diameter. (DWIinformation letter 16/99 and “The Guidanceon Assessing Risk from CryptosporidiumOocysts in Treated Water Supplies associatedwith the Water Supply (Water Quality)(Amendment) Regulations 1999”) [12].

A new drinking water Directive came intoeffect in December of 1998 [13] and TheWater Supply (Water Quality) Regulations2000 [14] transpose the 1998 Directive for

English water companies. These Regulationswill come into force over time, mostly inDecember 2003. However, certain parts notdirectly related to the new directive came intoeffect on the 1 January 2001. TheCryptosporidium monitoring provisions havebeen enacted early to provide continuity ofmonitoring initiated under the 1999Regulations [6].

Regulation of private water supplies.Local authorities regulate private suppliesunder the Private Water Supply Regulations1991 [15]. The Regulations contain the samewater quality standards as those for publicdrinking water but the frequency of testingand the parameters tested vary according tothe number of people using the supply or thedaily volume of water used. The Regulationsdo not require private supplies to bemonitored specifically for Cryptosporidium.

Acknowledgement

Section I. has been produced from a précis ofthe sections on the regulatory framework forpublic and private water supplies andCryptosporidium Regulations in the ChiefInspectors Report for 2000 and 2001 on theDWI’s web site, under the terms of the CrownCopyright permission.

The full texts are available atwww.dwi.gov.uk/pubs/annrep01/index.htmfor the 2001 reportandwww.dwi.gov.uk/pubs/annrep00/index.htmfor the 2000 report

or from HMSOFor more information on the work of theDWI seewww.dwi.gov.uk/


Animal Cryptosporidiosis

209

3. Animal Cryptosporidiosis - Allerdale and Copeland

A Animal Census

The Agricultural and Horticultural censuspublished annually by Department ofEnvironment, Food and Rural Affairs (Defra),and previously by its predecessors theMinistry of Agriculture, Food and Fisheries,(MAFF), provided information on number offarms, farm workers, sheep and cattlepopulations in the local authorities ofAllerdale and Copeland. Table 12 is thesummarised census data for the Years 1996 to2001. The data collected annually, referred tothe previous year statistics. The data shown inthe tables are the actual statistics for that year.Foot and Mouth disease was rife in 2001throughout the study area.

The census statistics for the Years 1996 to2000 provided an overview of the consistentlarge numbers of animals throughout the 5years. More than 600,000 sheep, 300,000young lambs, 100,000 total cattle and calves,40,000 cattle and calves under 1 year, wereseen each year. The numbers did not showany marked decrease over the five years.Generally, it would appear that Allerdale hadmore farms and at least three times moreanimals than Copeland, but it is also abouttwice the size in the total area on holdings(hectars). It would also appear that there wasa decrease in number of dairy farms from1996 to 2000.

The census data reported a substantialdecrease in cattle and sheep in the year 2001because of the Foot and Mouth outbreak. Thestatistics shown in table 12 may not be acomplete record of the total numbers ofanimals involved in the outbreak in the studyarea. The Foot and Mouth outbreak ended on20 January 2002 and data collection may havebeen done in mid or end of the year 2001.


Animal Cryptosporidiosis - Census

210

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Animal Cryptosporidiosis - Census

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The Veterinary Laboratories Agencyexamined animal faecal specimens sent in bypost or from post-mortem carcasses forCryptosporidium. The examination would bepart of the investigation into the cause ofdiarrhoea in an individual animal or group ofanimals, as part of the tests for viruses andbacteria. In almost all cases the sampleswould have originated from either calves orlambs less than one month old. Thesespecimens represented only a smallproportion of calf/lamb diarrhoea cases, as themajority would have been treated by theprivate vet without investigation.

The Veterinary Laboratories Agency providedinformation on cattle and sheepCryptosporidium isolates in the study areafrom 1996 to 2000 (Table 13). These isolatesin Allerdale and Copeland were comparedwith the total number found in the whole ofCumbria. The number of isolates in Allerdaleand Copeland in proportion to totalCumbrian isolates represented 23 (21%) inAllerdale and 8(7%) in Copeland in 1996,50(26%) in Allerdale and 10(5%) inCopeland in 1997; 52(24%) in Allerdale and13(6%) in Copeland in 1998; 68 (35%) inAllerdale and 6 (3%) in Copeland 1999;66(27%) in Allerdale and 14(6%) inCopeland in 2000.

Allerdale featured on average five times (range3 - 10 times) as many cattle and sheep isolatesthan Copeland. Examination of the positiveisolates by month showed marked increase inthe months of March, April, May with asmaller peak in October, November, andDecember. This pattern reflected the seasonallambing and calving patterns.

Examination of positive cryptosporidiosis incattle and sheep in relation to total number of

samples submitted to the local VeterinaryLaboratories Agency in 1999, showed theseasonal increases for both sheep and cattle inthe months of March, April, and May (Table14). However, whilst cattle faecal specimenswere submitted throughout the year andcorresponding cryptosporidiosis isolates werefound, sheep faecal specimens were onlysubmitted in the spring (Figure 11, 12).

Year 2001 was marked by the Foot andMouth outbreak, which affected the whole ofthe study area. The Veterinary LaboratoriesAgency was involved in assisting this outbreakand reports of animal cryptosporidiosis werenot available for the years 2001 and 2002.


Animal Cryptosporidiosis - Animal Isolates

212



213

Table 13 Animal Cryptosporidium Isolates reported by the Veterinary Laboratory Agency

1996 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

% of Cumbrian

Cryptosporidium

Isolates

Allerdale Cattle 4 1 1 2 0 1 3 1 1 4 2 3 23

Sheep 0 0 0 0 0 0 0 0 0 0 0 0

Copeland Cattle 0 0 1 0 3 0 0 0 1 0 0 3 8

Sheep 0 0 0 0 0 0 0 0 0 0 0 0 0

Other Cattle 9 2 3 5 11 7 2 3 1 4 6 18 71

Cumbria Sheep 1 0 1 2 6 0 0 0 0 0 0 0 10

Total Cumbria per month 14 3 6 9 20 8 5 4 3 8 8 24 112

21%

7%

72%

100%


% of Cumbrian

Cryptosporidium

Isolates


Sheep 0 0 1 4 1 0 0 0 0 0 0 0 6

Copeland Cattle 2 1 0 0 1 0 1 0 0 0 0 0 5

Sheep 0 0 1 0 0 0 0 0 0 0 0 0 1

Other Cattle 7 8 12 28 18 5 5 3 3 1 2 12 104

Cumbria Sheep 0 0 1 7 8 0 1 0 0 0 0 0 17


3%

62%

100%

35%


% of Cumbrian

Cryptosporidium

Isolates


Sheep 0 1 2 3 3 0 0 0 0 0 0 0 9

Copeland Cattle 1 1 3 3 1 1 0 0 0 0 1 1 12

Sheep 0 0 0 0 1 0 0 0 0 0 0 0 1

Other Cattle 11 12 14 18 13 12 5 6 5 5 10 10 121

Cumbria Sheep 0 0 0 12 15 0 0 0 0 0 0 0 27

Total Cumbria per month 14 16 23 46 42 13 6 9 6 10 14 14 213 100%

24%

6%

69%


% of Cumbrian

Cryptosporidium

Isolates


Sheep 0 0 0 0 1 0 0 0 0 0 0 0 1

Copeland Cattle 2 0 0 2 1 2 0 1 0 1 0 0 9

Sheep 0 0 0 0 1 0 0 0 0 0 0 0 1

Other Cattle 13 9 12 15 20 9 9 2 1 7 6 9 112

Cumbria Sheep 0 1 0 8 5 3 0 0 0 0 0 0 17


26%

5%

68%

100%

TABLE 13 ANIMAL CRYPTOSPORIDIUM ISOLATES REPORTED BY THE VETERINARYLABORATORY AGENCY



214

Table 13 (Continued) Animal Cryptosporidium Isolates reported by the Veterinary Laboratory Agency


% of Cumbrian

Cryptosporidium

Isolates


Sheep 0 0 0 2 4 0 0 0 0 0 0 0 6

Copeland Cattle 1 4 2 0 2 1 1 0 0 0 0 1 12

Sheep 0 0 0 1 1 0 0 0 0 0 0 0 2

Other Cattle 9 13 7 21 35 10 5 5 3 4 11 12 135

Cumbria Sheep 0 2 3 13 11 1 0 0 0 0 0 0 30


27%

6%

67%

100%

2002(Note2) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

% of Cumbrian

Cryptosporidium

Isolates

Allerdale Cattle 0

Sheep 0

Copeland Cattle 0

Sheep 0

Other Cattle 0

Cumbria Sheep 0

Total Cumbria per month 0 0 0 0 0 0 0 0 0

1) Data only available up to end of January 2001

2) Most Cumbrian farms declared Foot & Mouth disease free and decontaminated and able to restock 31/01/2002

No reports available due to Foot & Mouth

disease outbreak and Laboratory's

involvement in this.

0%

0%

0%

0%

E

n

d

o

f

S

t

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d

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2001(Note1) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

% of Cumbrian

Cryptosporidium

Isolates

Allerdale Cattle 7 7

Sheep 0 0

Copeland Cattle 0 0

Sheep 0 0

Other Cattle 7 7

Cumbria Sheep 0 0


50%

No reports available due to Foot & Mouth disease outbreak

and Laboratory's involvement in this.0%

50%

100%

TABLE 13 (CONTINUED) ANIMAL CRYPTOSPORIDIUM ISOLATES REPORTED BY THEVETERINARY LABORATORY AGENCY



215

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9


Animal Cryptosporidiosis - Links Between Human & Animal Cryptosporidiosis

218

C Link between human cryptosporidiosis and animalcryptosporidiosis

In collaboration with the VeterinaryLaboratories Agency, the cases in the casecontrol study were further examined forpossible links with laboratory confirmedanimal cryptosporidiosis identified by theLaboratory (Tables 15, 16).

From the case questionnaires, note was madeof a case who reported contact with a farm oranimals in a farm, in the two weeks prior toonset of illness. A check would then be madewith records held in the VeterinaryLaboratory to ascertain whether the namedfarm had an animal with laboratoryconfirmed cryptosporidiosis in the twomonths before and after the date of illness ofthe human case. The result of this checkwould be classed as a ‘hit’ if animalcryptosporidiosis was present 2 months priorto onset of human case, ‘may be’ if 2 monthsafter the human case, and ‘miss’ if no animalcryptosporidiosis was present. The LocalEthics of Research Committees approved thisconfidential checking exercise. Names ofcases were not divulged and confidentialdetails were not published.

The results showed that for the period of thestudy 1996 to January 2001, 52 casesreported contact with a farm or animals in afarm (Table 15, 16). Of these, 48 were notfound to have links with laboratoryconfirmed animal cases; 2 were classed‘maybe’ indicating laboratory reports ofanimal cryptosporidiosis appeared twomonths after the human case. There were alsotwo ‘hits’ indicating that there were two caseswith positive links to laboratory confirmedanimal cryptosporidiosis identified twomonths before the human case.

This was a crude method of examination, andwas reliant on many factors, not least thevoluntary submission of an animal faecalsample by the farmer, which also has costimplications. Each positive result wasgenerally representative of isolates in a herd,and was likely to suggest the presence ofcryptosporidiosis amongst the animals at thattime. Nevertheless, the results indicated thatthere were a small number of cases withpossible associations with farms and farmanimals.

No data was available from the VeterinaryLaboratories Agency in years 2001 and 2002because of the Agency’s involvement in theFoot and Mouth outbreak.



219

Where the number of farms (notified to the VLA) which the cases reported contact

within the two weeks prior to the onset of their illness are classed according to the

collaboration protocol’s Hit, Maybe or Miss scoring system (see definitions below).

Month Miss Maybe HitMar-96 3 0 0

Apr-96 3 0 0

May-96 1 1 0

Jun-96 0 0 0

Jul-96 0 0 0

Aug-96 0 0 0

Sep-96 2 0 0

Oct-96 0 0 0

Nov-96 0 0 0

Dec-96 0 0 0

Jan- 97 0 0 0

Feb-97 1 0 0

Mar-97 1 0 0

Apr-97 5 0 0

May-97 0 0 0

Jun-97 0 0 0

Jul-97 0 0 0

Aug-97 0 0 0

Sep-97 0 0 0

Oct-97 0 0 0

Nov-97 0 0 0

Dec-97 0 0 0

Jan-98 0 0 1

Feb-98 0 0 0

Mar-98 1 1 0

Apr-98 5 0 0

May-98 2 0 0

Jun-98 1 0 0

Jul-98 2 0 0

Aug-98 0 0 0

Sep-98 0 0 0

Oct-98 0 0 0

Nov-98 0 0 0

Dec-98 1 0 0

Jan-99 1 0 0

Feb-99 1 0 0

Mar-99 0 0 0

Apr-99 4 0 0

May-99 4 0 0

Jun-99 2 0 0

Jul-99 2 0 0

Aug-99 0 0 0

Sep-99 3 0 0

Oct-99 0 0 0

Nov-99 0 0 0

Dec-99 0 0 0

Definitions

Hit Case reporting contact with the farm at or <2

months after Cryptosporidia was recorded on the

farm.

Miss No Cryptosporidia was recorded on the

farm either two months before or after case

contact.

Maybe Case reported contact with the farm <2

months before Cryptosporidia was recorded on

the farm.

Month Miss Maybe HitJan-00 0 0 0

Feb-00 0 0 1

Mar-00 0 0 0

Apr-00 0 0 0

May-00 0 0 0

Jun-00 0 0 0

Jul-00 0 0 0

Aug-00 2 0 0

Sep-00 1 0 0

Oct-00 0 0 0

Nov-00 0 0 0

Dec-00 0 0 0

Jan-01 0 0 0

Feb-01

Mar-01

Apr-01

May-01

Jun-01

Jul-01

Aug-01

Sep-01

Oct-01

Nov-01

Dec-01

Jan-02

Feb-02

Mar-02

Apr-02

May-02

Jun-02

Jul-02

Aug-02

Total 48 2 2

No data

available due to

foot & mouth

disease and

Laboratory’s

involvement

with this

Jan-

TABLE 15 EXAMINATION OF THE LINKS BETWEEN HUMAN CRYPTOSPORIDIOSIS AND ANIMALCRYPTOSPORIDIOSIS

Where the number of farms (notified to the V L A) which the cases reported contact within thetwo weeks prior to the onset of their illness are classed according to the collaboration protocol’s`Hit , Maybe or Miss scoring system (see definitions below).



220

TABLE 16 EXAMINATION OF LINKS BETWEEN HUMAN CRYPTOSPORIDIOSIS AND ANIMALCRYPTOSPORIDIOSIS, SUMMARY FOR EACH YEAR

Score 1996 1997 1998 1999 2000 2001 2002 Total

Hit 0 0 1 0 1 0 0 2

Maybe 1 0 1 0 0 0 0 2

Miss 9 7 12 17 3 0 0 48

TOTAL 10 7 14 17 4 0 0 52


Wednesday, February 21 2001Farmers were today warned to check theiranimals after an outbreak of foot and mouthdisease among pigs was confirmed. Exclusionzone put in place around abattoir and farm inEssex.

Thursday, February 22Public warned to stay away from farms. ECbans UK exports of pork, beef, lamb, milkand milk products.

Friday, February 23Livestock movement ban introduced and allauction marts closed.

Tuesday, February 27Longtown farmers were on alert after thetown’s livestock market was linked to theoutbreak of foot and mouth disease. Majoroperation under way to trace the movementsof all workers’ vehicles and animals connectedwith this market. Twenty-five thousandanimals have been traced of which 13,000 arethought to have passed through LongtownMarket. Cumbria Wildlife Trust closes all its41 nature reserves. Ramblers Associationcancel all walks in Cumbria.

Wednesday, February 28Cumbria’s first suspected case of foot andmouth disease investigated. Special powers toclose footpaths and rights of way to the publicintroduced.

Thursday, March 1Foot and mouth disease confirmed inCumbria at Longtown.

Friday, March 2Cumbria Tourist Board warns that acampaign to keep tourists out of the LakeDistrict is over the top and will be devastatingfor businesses.

Saturday, March 3Announcement that nearly 19,000 sheep andcattle in Cumbria will have to be slaughteredand burned. Walkers who breach foot andmouth restrictions in the Lake District couldface fines up to £5,000.

Monday, March 5Eleven confirmed cases in Cumbria.Longtown confirmed as the link between thesource of the disease in Northumberland andan outbreak in the West Country. SevenCumbrian schools closed. Walkers forbiddento use public rights of way across farmland.Large parts of the Lake District closed.Fishermen warned to stay away from rivers.

Tuesday, March 6First case in West Cumbria confirmed. Hoteland restaurant owners unable to claimcompensation if tourism in the Lake Districtsuffers because of foot and mouth.

Friday, March 9Dead animals litter the fields awaitingincineration and Government is urged to sendin troops to tackle the backlog. Carlisle’sBorderway auction mart lays off 50 part-timestaff and puts full-timers on part-time work.Cumbria Young Farmers cancel all countymeetings and social events. Several touristvenues, including Muncaster Castle andRavenglass Railway, and the Coast to Coastcycle track are closed.

Tuesday, March 13The first case in France. Task force toconsider what can be done to overcome theeconomic and social consequences of theoutbreak has been set up by Cumbria CountyCouncil. Leaders of Cumbria’s NFU pleadwith the Government for more resources to bemade available to the county’s strickenfarmers. It is taking four or five days for thecarcases to be disposed of after slaughter.

D. Foot and Mouth Chronology

Thursday, March 15The Minister of Agriculture reveals massslaughter zones for all animals 3km aroundfoot and mouth infected farms. Ministerretracts statement to say cull applies only tosheep and pigs, not to cattle following massivepublic outcry.

Friday, March 16Carlisle Mobile Library Service stops.Cumbrian rugby union matches suspended.

Saturday, March 17County Council in talks over using sites atHespin Wood near Carlisle and Flusco nearPenrith to bury thousands of infected sheepand cattle. Emergency advice centres offeringsupport to people living in hot spots are to beopened by Carlisle City Council offeringadvice on a range of issues.

Monday, March 19Keswick traders plan protest saying manyworkers have already been laid off. Anguishfor farmers becomes intolerable as many waitto be told if their sheep will be killed underthe proposed 3km cull. Cumbria recognisedas being the worst affected county with morethan twice the number of confirmed cases asany other. Troops deployed for first time inCumbria.

Tuesday, March 20Businesses in rural Cumbria will receivecompensation for losses caused by foot andmouth epidemic. Measures being suggestedincluding halving business rates, deferringVAT payments, and halving rate relief forcertain businesses. Foot and mouth totalpasses 100.

Thursday, March 22Number of cases in Cumbria reaches 150.

Friday, March 23Foot and mouth in Cumbria could have long-term health implications for many peopledirectly affected by the crisis warns thecounty’s Public Health Director. Farming

losing £5 million a week, tourist losing £10million a week.The cull of healthy animals in Cumbria to bestarted within a few days as total number ofcases in the county rises to 165.Government’s Chief Scientist announces thatthe cull of animals within 3km of infectedfarms would apply throughout Britain, notjust to Cumbria and Devon.

Saturday, March 24Plans for mass slaughter sites around thecounty revealed. West Cumbrian branch ofthe Samaritans reports a surge in calls sincethe onset of the foot and mouth crisis.

Monday, March 26First case of foot and mouth disease on openland in the Lake District confirmed. The firstof 1/2 million sheep carcases arrive at GreatOrton airfield to be buried in a mass grave.

Friday, March 30Hundreds of businesses in Cumbria arestruggling to survive. Appleby Horse Faircancelled.

Monday, April 2BSE fear halts cattle burial. As Cumbriancases reach 400 the army announces that the24 hour target for slaughtering infectedanimals has been met. Plans for vaccinationabandoned for the time being.

Tuesday, April 10More than 100 footpaths and car parks havebeen opened across Cumbria in time forEaster.

Wednesday, April 11Cumberland County Show, Carlisle,cancelled.

Wednesday, April 14Sheep, pig and cattle carcases buried atHespin Wood near Carlisle. Cumbria is toget an immediate £2 million cash boost tohelp with foot and mouth and the state of theeconomy.


Animal Cryptosporidiosis - Foot & Mouth Chronology

222



223

Wednesday, April 18Health chiefs call for an immediate halt to anymore burning of animal carcases in Cumbriauntil all health risks have been investigated. Amini army of workers recruited to vaccinateanimals in Cumbria although no decision onvaccination yet made.

Saturday, April 21The backlog of animal carcases waiting to bedisposed has been cleared in Cumbria. It hasbeen estimated that up to 100,000 deadanimals lying across the county with manylying for up to 10 days. Infected farms nowall being culled within 24 hours andneighbouring farms within the 48 hourdeadline.

Thursday, April 26Government’s promise of slaughtering healthyanimals relaxed today.

Tuesday, May 1Lowther horse driving trials and country faircancelled.

Monday, June 7General election. MAFF becomes Defra.

Saturday, June 9Some of Cumbria’s most famous Lakelandfells re-open - at 29 access and disinfectionpoints.

Sunday, July 1New FMD cases, mainly in the area ofPenrith, sparks fears of a resurgence of disease.

Friday, July 13Number of animals slaughtered in Cumbriareaches one million.

Wednesday, July 18Plans to re-open public paths across nearlyhalf of Cumbria announced, to begin onAugust 1st.

Wednesday, August 1Eight new cases in Penrith Spur. Highestnumber in a single day for more than threemonths.

Tuesday, August 7Tough biosecurity measures introduced in thePenrith Spur to halt foot and mouth. Fivebiosecurity points set up to disinfect vehiclesusing pressure washers.

Friday, August 24Foot and mouth restrictions set to be lifted inlarge areas of North Cumbria. Outbreak inPenrith Spur appears to be out of control.

Thursday, August 30Longtown market re-opens.

Tuesday, September 4The 2,000th case nation-wide was reported inCumbria.

Thursday, September 27The foot and mouth crisis has cost Cumbria’scouncil taxpayers £1.88 million so far. Theauthority has incurred costs of £3.71 million,of which £1.83 million will be met by theGovernment. The biggest expense wasdisinfectant mats at £2.14 million.

Sunday, September 30Last confirmed case of foot and mouth diseasein the country.

Monday, October 1Around 12,300 Cumbrian jobs have been putat risk by foot and mouth with 3,000 seasonaljobs in the county being totally scrapped saysthe Cumbria Rural Task Force.

Thursday, October 4Tough movement restrictions for Cumbrianfarmers have been relaxed to allow farmers tomove stock more easily this autumn.

Wednesday, October 10Foot and mouth restrictions have been liftedon nearly 6,500 farms in North and WestCumbria following the completion of bloodtests on all sheep in these areas. Movement oflivestock under licence will now be permitted.

Wednesday, October 17First live sale at Lockerbie Market for eightmonths.

Friday, October 19Reported today that Cumbria lost a third ofits Herdwick sheep and two-thirds of itsRough Fell sheep.

Monday, December 31Cumbria finally declared free of foot andmouth disease at midnight on New Year’s Eve.

2002

Tuesday, January 15Foot and mouth disease epidemic officiallydeclared over in the UK whenNorthumberland, the last county underrestrictions, was pronounced free.

Monday, 21 JanuaryThe Office des International Epizootes (OIE)has declared that the United Kingdom hasregained its previously recognised foot andmouth disease-free status withoutvaccination.

Monday, February 18Cumbria’s first livestock sale since lastFebruary held at the Borderway Mart,Carlisle.

Friday, February 22Longtown Mart re-opens.

Cumbria County Council announces that itwill hold its own local enquiry into foot andmouth.

Tuesday, February 26First public sale of animals for more than ayear held at Penrith Farmers & Kidd’sAuction.

Thursday, May 9Sheep and goat, store and breeding, marketshave re-opened for the first time since theFMD outbreak.

Useful links:www.cumbria.gov.uk/news/footandmouth/www.defra.gov.uk/footandmouth/wnew.htm



224


Human Cryptosporidiosis Outbreaks

225

During the period of the study, there were norecognised outbreaks of cryptosporidiosis inthe study area.

A cluster of cases was noted in the study areabetween the 23rd and the 30th April 1999.There were 14 confirmed cases in this period,9 in the Allerdale local authority area. Thesewere independently investigated by theCCDC for North Cumbria Health Authority,who convened a meeting on the 26th April.

A second meeting was held on the 30th April2000 at which all the available evidence wasreviewed. The investigations showed thatthere were no common links between caseswith any particular risk factor/s.

No further excess of cases was noted after thisdate and no conclusive evidence wasidentified to confirm that an outbreak hadoccurred.

4.Human cryptosporidiosis outbreaks


Cryptosporidiosis CaseCryptosporidiosis Case--control Study Timescale 1996control Study Timescale 1996--2002.2002.

National InfluencesNational Influences Influences onInfluences onthe studythe study

Local influencesLocal influences

19961996

January

February

March 1st March -Start of case-control study

April 1st April -Research Assistant EW appointed

May

June

July

August

September

October

November

December

19971997

January

February

March

April

May

June

July

August

September 1st Interim Report available includingstatistics up to 30th June 1997.30th Sept. -Research Assistant EW leaves

October EHO’s continued interviews.

November

December

19981998

January

February

March

April 1st April -Research Assistant JW appointed

May

June

5.Chronology of Study


Chronology of Study

227




19981998

July

August 4 day Boil Water Notice: Crummock Water

September 2nd Interim Report available includingstatistics up to 31st Aug 1998.Validation of data between NCHA& CDSC.

October

Third Report of Group of Experts on Crypto-sporidium in Public Water Supplies pub-lished.

November

December

19991999

January

February

March E. coli outbreak: Cockermouth

Manchester –North West Outbreak. April Increased local media activity and study

May Increased local media activity and study

30th June New Water Quality Amendmentregulations came into force.

June Media Interest study continuing

July Media Interest study continuing

August Media Interest study continuing

September Media Interest study continuing

October Media Interest study continuing

November Media Interest study continuing

December Media Interest study stopped.Statistics up to 31st Aug 1999 available.

20002000

January

February 29th Feb. deadline date for pre-interventionData.

Cryptosporidium Outbreak in Clitheroe, Lan-cashire (CDR Weekly Vol 10 Number 13)

March Filter commissioning begins at EnnerdaleWTW and Cornhow a few weeks later.

April Ennerdale now providing continuous microfil-tration of water to remove Cryptosporidium

May

Continuous monitoring samples for Crypto-sporidium along the Thirlmere Aqueduct failthe treatment standard. No outbreak identi-fied.

June

July Filter commissioning ends at Cornhow.

August Cornhow now providing continuous microfil-tration of water to remove Cryptosporidium.

October

November

December

Cryptosporidium Outbreak in Northern Ire-land (CDR Weekly Vol 10 Number 36)

September


Chronology of Study

228




20012001

January

Foot & Mouth disease confirmed at Heddonon the Wall, Northumberland 21/02/2001

February First case of F&M in study area confirmed28/02/2001 (See detailed Chronology in Sec-tion III, subsection 3D)

Access to large areas of the Countryside re-stricted due to the F&M disease restrictions.

March A Pennington appointed as Research Assistant12th March 2001. Large parts of the study areahave restricted access to agricultural land.

April

May

June

July

August F&M restrictions lifted in parts of the studyarea but Northern Allerdale still affected.

Last confirmed case of F&M in the country. September

October

November

December Cumbria declared F&M free.

20022002

UK F&M epidemic declared officially over. January

(21..01..2002 February Draft Pre intervention statistical analysis avail-able. Steering Group Meeting. 27.02.2002

March

Cryptosporidium Outbreak in Northern Ire-land (CDR Weekly Vol 11 Number 18)

April

May

June

July

August End of Intervention Study

October Last Steering Group Meeting. 17.10.2002.Preparation of final reports. Post interventionanalysis prepared.

November Preparation of final reports.

December Completion of research project.

September Preparation of final reports.


Section III References

229

7. Section III References

1. Cumbria County Council. Population change inurban areas 1991 to 2002. Briefing 05/2002,Information & Communications, The Courts,Carlisle.

www.cumbria.gov.uk/briefings/2002/brf0502.pdf

2. Statutory Instruments 1989 No. 1147. The Water Supply (Water Quality) Regulations1989. HMSOwww.dwi.gov.uk/regs/si1384/1384.htm

3. Badenoch J. Cryptosporidium in water supplies:Report of the Group of Experts. London:Department of Environment, Department ofHealth, HMSO 1990

4. Badenoch J. Cryptosporidium in water supplies:Second Report of the Group of Experts. London:Department of Environment, Department ofHealth, HMSO 1995

5. HMSO. The Water Industry Act 1991 (c. 56),ISBN 0105456918, The Stationery OfficeLimited.

www.hmso.gov.uk/acts/acts1991/Ukpga_19910056_en_1.

htm

6. Statutory Instruments 1999 No. 1524. The Water Supply (Water Quality) (Amendment)Regulations 1999. HMSO.

7. US Filter Memcor(r) Membrane Technology.Potable Water Treatment Technical Data andbackground information on process selection atEnnerdale WTW, Memcor Ltd, Derby Road,Wirksworth, Derbyshire. Information packprovided by United Utilities. Also see US Filterwebsite and technical manual. www.usfilter.com/priv_elib/Objects/25062_MCTD%2002

99.pdf

8. Drinking Water Inspectorate. Guidance on Low-pressure membrane integrity monitoring. DWIinformation letter 3/2002.www.dwi.gov.uk/regs/infolett/2002/info0302.htm

9. North West Water Ltd. (NWW).Cryptosporidium and Giardia in Water, Isolation,Identification and Enumeration via membranefiltration method and flow cytometry. LaboratoryServices Quality System, QI 242/04 24/08/1999.

10. North West Water Ltd. (NWW).Cryptosporidium and Giardia in Water, Isolation,Identification and Enumeration via membranefiltration method and ImmunomagneticSeparation. Laboratory Services Quality System,QI 242/04 08/05/2000.

11. Council Directive 80/778/EEC of 15 July 1980relating to the quality of water intended forhuman consumption OJ No. L229, 30.8.80, p11.

12. Drinking Water Inspectorate. DWI informationletter 16/99 and “The Guidance on AssessingRisk from Cryptosporidium Oocysts in TreatedWater Supplies associated with the Water Supply(Water Quality) (Amendment) Regulations 1999”www.dwi.gov.uk/regs/infolett/1999/info1699.htm

13. Council Directive 98/83/EC of 3 November1998 on the quality of water intended for humanconsumption, OJ No. L330, 41, 5 December1998, p32.

14. Statutory Instruments 2000 No 3184. The WaterSupply (Water Quality) Regulations 2000.HMSO.

www.dwi.gov.uk/regs/si3184/3184.htm

15. Statutory Instruments 1991 No. 2790. PrivateWater Supplies Regulations 1991. HMSO.


Section IVAppendices


Appendices - Questionaire

232

PHLS Communicable Disease Surveillance Centreand North Cumbria Health Authority

CRYPTOSPORIDIOSISCRYPTOSPORIDIOSISCRYPTOSPORIDIOSISCRYPTOSPORIDIOSIS

IN WEST CUMBRIAIN WEST CUMBRIAIN WEST CUMBRIAIN WEST CUMBRIA

NOTES: Check subject has not taken part in the study previously.

If a parent is answering the questions on behalf of a child, substitute “your child” for “you” in every

question. Ensure parent gives answers which correspond to the child ONLY.

Please tick boxes or write in the spaces provided.

Serial No Case 1 Control 2

Interview date ____/____/____ Interviewer’s Initials ________

PERSONAL DETAILS

Forename _______________________ Surname ______________________________________

Sex Male 1 Female 2 Age years

_________ months (if aged less than 1 year)

Address ______________________________________________________________________

______________________________________________________________________

Postcode ______________________ Telephone ____________________________________

Allerdale Copeland

Water Supply Zone ___________ Local Authority 1 2

Occupation

School Nursery Works with Agricultural Other Unknown

child child children

1 2 3 4 5 9

Contact with play group/nursery Yes 1 No 2

Address of place of work/school/nursery _______________________________________________

_________________________________________________________________________________

Postcode ________________________ Water Supply Zone ___________

1. Have you been ill recently with diarrhoea?

(CASES: in the 2 weeks before stool specimen taken CONTROLS: in the 2 weeks before interview)

Yes 1 No 2 If NO, go to Q8 (P3)



233

2. GP's name _____________________________________________________________

GP’s address _____________________________________________________________________

3. When did your illness start? ____ /____ / ____

4. Is your illness continuing? Yes 1 No 2

If NO, for how many days were you ill?

5. Did you have any of the following symptoms?

Yes No Not sure

a) Diarrhoea 1 2 8

b) Fever 1 2 8

c) Abdominal pain 1 2 8

d) Vomiting 1 2 8

e) Loss of appetite 1 2 8

f) Weight loss 1 2 8

If Other, please specify _______________________________________

6. Were you admitted to hospital for this illness? Yes 1 No 2

If YES, which hospital? _______________________________________________

7. Did anyone in your household have diarrhoea in the 2 weeks before you became ill?

Yes 1 No 2

Relationship to case Date of onset Diagnosis if known

_______________________ __________________ ______________________

_______________________ __________________ ______________________



234

8. Did you have contact with anyone with diarrhoea, in the past 2 weeks before illness (case)/interview

(controls)?

Yes 1 No 2

If YES please specify:-

Relationship e.g. relative, friend Date of onset of illness Duration of contact

_______________________ __________________ ________________

_______________________ __________________ ________________

NB Continue interview and investigate contact later (note names and addresses below)

Name Address/contact phone

_____________________ _____________________________________

______________________ _____________________________________

______________________ _____________________________________

______________________ _____________________________________

9. In the 2 weeks before onset of illness (cases)/date of interview (controls), did you spend any nights away

from home?

Yes 1 No 2 Unknown 8

IF YES, where did you go?

Town/country visited No. of nights away Local* UK Abroad

____________________ 1 2 3

____________________ 1 2 3

*Within the study area

10. In the 2 weeks before onset of illness (cases)/date of interview (controls), how many days did you spend

at work/school?

Consumption of water:

11. Type of water supply at home:

Mains 1 Private 2 Both 3 If not mains, please specify _________________



235

12. Was there any disruption in mains supply in the week preceding illness (cases) /interview (controls)?

Yes 1 No 2 Not sure 8

If YES, give details _________________________________________________________

13. Was the water discoloured in the week preceding illness (cases) /interview (controls)?


If YES, was this in: Mains supply 1 Private supply 2

14. Do you usually drink cold tap water or drinks containing cold tap water (without boiling it first)?


If YES:-

About how much cold (unboiled) tap water (including water diluted in squash/fruit juice) do you usually

drink per day? [Refer to instruction sheet on volumes e.g. 1 glass = 1/3 pint]

a) At home (number of pints on average) ___________ pints

b) Away from home/at work/nursery/school ___________ pints

(number of pints on average)

c) Did you drink water outside Copeland and Allerdale LA? Yes 1 No 2

(From b)

15. In the 2 weeks before illness (cases) / interview (controls), did you have any drinks with ice added?


If YES: at home 1 at work/nursery/school 2 elsewhere, specify _____________________

16. Do you usually drink bottled water?

Yes 1 No 2 Not sure 8 Brand _______________________

If YES, about how much bottled water (on average) do you drink per day _______ pints



236

17. Do you usually drink soft drinks?

Yes 1 No 2 Not sure 8 Brand _______________________

If YES, about how much soft drinks (on average) do you drink per day _____ pints

18. In the 2 weeks before illness (cases) / interview (controls) did you go swimming?


If YES, where: ____________________________________________________

About how many times?

19. In the 2 weeks before illness (cases) / interview (controls) did you go boating, wind-surfing, water-skiing

or canoeing?


If YES, where: ____________________________________________________


20. In the 2 weeks before illness (cases) / interview (controls) did you go paddling?


If YES, where: ____________________________________________________


21. Did you have any other contact with fresh water (eg. other water sports, fishing)?

Yes 1 No 2 Not sure 8 Specify _______________________



237

22. In the 2 weeks before illness (cases) / interview (controls), about how often did you eat the following:

not at all 1-2 times 3-7 times most days not sure

Salads:

Lettuce 0 1 2 3 8

Tomatoes 0 1 2 3 8

Coleslaw 0 1 2 3 8

Mixed salad 0 1 2 3 8

Brand and Shop

Raw sausages 0 1 2 3 8 ________________

Other uncooked meats 0 1 2 3 8 ________________

Name of Supplier/Shop

Fresh raw vegetables 0 1 2 3 8 ________________

Cheese (raw)

Locally produced 0 1 2 3 8 ________________

Other 0 1 2 3 8 ________________

Yoghurt 0 1 2 3 8 ________________

Ice Cream 0 1 2 3 8 ________________

Cream 0 1 2 3 8 ________________

23. In the 2 weeks before illness (cases)/interview/(controls), did you drink pasteurised milk?


If YES:- Supplier/Brand/Shop ___________________________________________

About how much pasteurised milk on average do you usually drink per day _____ pints

(insert number of pints using picture reference as guide)



238

24. In the 2 weeks before illness (cases)/interview/(controls), did you drink unpasteurised milk?


If YES:- Supplier/Brand/Shop ___________________________________________

About how much unpasteurised milk on average do you usually drink per day _____ pints

25. In the 2 weeks prior before illness (cases)/interview (controls), did you have contact with animals at

home, for example, pets?


If NO, go to Q28

If YES, please list all your pets, the type of contact (eg. stroking only, licked by dog/cat) and where they

are kept overnight (eg. kennel outside, sleep on owners bed).

TYPE OF PET

Dog Cat Rabbit Guinea pigs Fish Hamster Other

/Gerbil

Other, please specify __________________________

TYPE OF CONTACT

Stroking Feeding Licking Other

by hand by pet contact Specify

Dog ______________________________

Cat ______________________________

Rabbit ______________________________

Guinea pigs ______________________________

Reptile ______________________________

Horse ______________________________

Other ______________________________



239

WHERE KEPT OVERNIGHT

Outside In house, In Kitchen In house,

House in bedroom elsewhere

Dog 1 2 3 4

Cat 1 2 3 4

Rabbit 1 2 3 4

Guinea pigs 1 2 3 4

Reptile 1 2 3 4

Horse 1 2 3 4

Other 1 2 3 4

26. In the 2 weeks before illness (cases)/interview (controls), did any of your pets have diarrhoea?


FOR CASES ONLY:-

If YES, and you were also ill, did your pet’s illness occur before or after your illness?

Before 1 After 2 Not sure 8

27. What do you feed your pet(s) on?

Raw Tinned Pellets Biscuits Left- Raw Other

meat meat overs vegetables

28. In the 2 weeks before illness (cases)/interview (controls), did you have contact with fields recently

sprayed with slurry?


If YES, please specify:-

Type of contact

Walking Close Other

Field (where) How many times by (in field)

________________________ ______________

________________________ ______________



240

29. In the 2 weeks before illness (cases)/interview (controls), did you have contact with farms?



Name of farm Type of Farm How Many Times Type of contact

Dairy Cows/ Mixed Other Short Overnight Other

Sheep visit stay

________________ _________

________________ _________

30. In the 2 weeks before illness (cases)/interview (controls), did you have contact with farm animals?

(including animals such as cows, lambs, pigs, goats etc, brought to school or nursery etc)



a) Animal Where How many times Type of contact

(eg. farm, zoo, nursery) Feeding

Stroking by hand Other None

_______________ ______________________ _________

_______________ ______________________ _________

_______________ ______________________ _________

_______________ ______________________ _________

b) Did this contact with farm animals include feeding any of them?


c) Did you/your child eat any food within 1-2 hours of contact with these farm animals ?


If YES, where was the food eaten: ______________________________

Was hand-washing carried out before eating:




241

31. In the 2 weeks before illness (cases)/interview (controls), did you have contact with any other animals or

birds (excluding farm animals ), eg. at a friends or neighbours house, work, at a zoo, or while outside

(eg. walking or gardening) and including any animals at nursery school that you/your child help to look

after?


If YES, please specify animals, where you/your child came into contact with them, the frequency and type of

contact:-

Animal Where How many times Type of contact

(eg. friend, zoo)

Stroking Licking Other

_______________ ______________________ _________

_______________ ______________________ _________

_______________ ______________________ _________

_______________ ______________________ _________

32. In the 2 weeks before illness (case)/interview (control) did you/your child accidentally touch any

dirt/faeces from any animal?


If YES, please give details:-

_____________________________________________________________________________

33. What type of sewerage system do you have?

Mains sewerage system 1

Septic tank 2

Other 3

If other, please specify: ___________________________________________________________

Thank you for completing this questionnaire.

If you have any comments you think may be useful, please use the space below.

_____________________________________________________________________________

_____________________________________________________________________________

Laboratory ________________ Lab Number ______________ Date of report ____/____/____


Appendices - Leaflet

242

CRYPTOSPORIDIOSIS STUDY IN NORTH CUMBRIAQUESTIONS AND ANSWERS

1 What is Cryptosporidium and howdoes it affect humans?It is a protozoan parasite that iscommonly found in cattle, sheep andsome other animals. In humans it cancause acute gastroenteritis symptomssuch as diarrhoea, abdominal pains,nausea, vomiting, low-grade fever andheadache. These acute symptoms canlast from 1-3 weeks, but some symptomscan persist for up to 6 weeks.

2 How is it transmitted?Cryptosporidiosis, the disease, can beacquired by the faecal-oral route (fromone person to another), directly fromanimal contact to man, or throughingestion of contaminated water, milk, orsome foods.

3 Can the germ be killed?Cooking or raising water to boiling willkill the germ.

4 How can I avoid catching it?The study will try to trace the source ofinfection in the cases in from March1996. Practising good hygiene willreduce the risk of this germ spreading toother family members or contacts.

5 Who is more at risk of getting theinfection?People with low immunity, childrenunder 5 years and some categories ofimmunocompromised people are more atrisk.

6 What is the study in North Cumbria?From March 1996, a detailed cryp-tosporidiosis study has been taking placein Allerdale and Copeland (North

Cumbria). This started on the 1st March1996 and will continue for several yearsuntil the year 2002. Anyone who is illwith cryptosporidiosis and lives inCopeland and Allerdale will be asked totake part in the study.

Information given by these cases will becompared with information given by wellpeople who live in the same geographicalarea.

A Research Assistant will visit andinterview the cases and the comparablewell persons at home.

7 Why is the study taking so long?In the first 2 years of the study, aninsufficient number of cases wereobtained. Whilst this is good that fewerpeople became ill, it did not help thenumbers in the study and we could notget a conclusive result/results. It alsohighlighted the problem of the unpre-dictability of a study that looks at casesthat has not yet occurred and not becausethere is an existing problem.

Adding more cases over several years willhelp to get better results, and to allowstudy of the infection in our population.

8 Does my Doctor know about theStudy?Yes, your own GP will have beeninformed about the study. If you are acase, he will have your laboratory result.

9 Will details of my illness orinformation be given out to the publicNo. The information is totallyconfidential. Names of people andaddresses will not be used to give out toothers in any report, or published. Theinformation obtained at the interview



243

will be added to information from othercases/controls and analysed together.The results will then be published incombined form. Individual details willnot be identifiable.

10 What are the aims of the Study?The cryptosporidiosis study aims to lookat whether there are links between thecases from March 1996 in a detailed,scientific way.

11 Why are you studying Copeland andAllerdale?We noticed that in 1994 and 1995 therewere more cases in Copeland andAllerdale when compared with CarlisleCity and Eden. Routine investigations,however, did not reveal a common linkbetween the cases and there were nomajor outbreaks in those 2 years. Thestudy may help to shed more informationon cases that are not associated withoutbreaks.

12 Can I refuse to take part?Yes you can. The study is entirelyvoluntary. However, your co-operationwill be greatly appreciated. The results ofthe study will help us to know where theinfections are coming from and alsoabout the germ, and the results could beused to help interpret results in both ourdistricts, and other districts.

13 Has ethical approval been given?Yes, both the Ethics of ResearchCommittees in East and West havelooked at the study and given theirapproval.

14 Who are taking part in the study?The study is a joint one between thelocal authorities of Copeland BoroughCouncil, Allerdale Borough Council,North Cumbria Health Authority (Fromthe 1st April 2002, the North CumbriaPublic Health Department, Carlisle &District NHS Primary Care Trust) andthe Communicable Disease SurveillanceCentre in London.

15 What normally happens if I havecryptosporidiosis and when the studyis not taking place?All cases of cryptosporidiosis areroutinely investigated by theEnvironmental Health Officers to tryand trace the source of infection. Theywill also give advice to cases.

16 Is there antibiotic treatment for thisinfection?At the present time, there is no specificantibiotic for this infection. Therefore,treatment is mainly to make sure that theill person is not dehydrated.

17 When is the infective period?The most infectious period is when thediarrhoea is present. On occasions, thesesymptoms may linger or recur off andon.

Statistics Rate/ Rate/1994 Cases 100,00 1995 Cases 100,000

Allerdale/Copeland 54 32.2 52 31.1

Carlisle City/Eden 36 23.9 30 19.9



244

18 When can my child return tonursery/school?It is recommended that the child is keptoff nursery/school all the time he/she hassymptoms or is unwell. When thesymptoms have stopped, it is advisablethat you should allow a period of 48hours symptom free before allowing yourchild to return to nursery/school. This isstandard protocol. Practising goodhygiene will still be very important; bothat the time when symptoms are presentand also after symptoms have stopped.

19 Can I be identified in the study?No, the report when it is published willonly contain results in a combinednumbered form. Individual names willnot be in the report.

20 When can I see the results?The results will be published when thestudy is completed in 2002. We cannotspeculate on results until the study iscompleted. This study is unique in thatit is looking at cases as and when theyoccur, and not because there is anexisting problem or outbreak.

The above are the main questions and answers.If you have any further queries please ask theResearch Assistant or Environmental HealthDepartments or Dr S K Goh, Consultant,North Cumbria Cryptosporidiosis ResearchGroup, who may be able to assist.

Miss Mary Cosgrove, Telephone No. 01946 852941 (during office hours)

EHO, Copeland Borough Council

Mr David Copeland, Telephone No. 01900 326430 (during office hours)

EHO, Allerdale Borough Council

Dr S K Goh,Telephone No. 01228 603500 (during office hours)

Honorary Consultant,North Cumbria Cryptosporidiosis Research Group,North Cumbria Health Authority(From the 1st April 2002, the NorthCumbria Public Health Department, Carlisle & District NHS Primary Care Trust)

Mr Anthony Pennington,Telephone No. 01946 852619 (during office hours)

Research Assistant,Copeland Borough Council


Appendices - Pictorial Leaflet

245


Appendices - Letters

246

Wavell DriveRosehillCarlisle

CA1 2SE

Tel: 01228 603500Fax: 01228 603612

www.ncumbria.demon.co.uk

Dear Sir/Madam

CRYPTOSPORIDIOSIS STUDY IN COPELAND AND ALLERDALE

I understand that you or your child recently had been ill with gastroenteritis and was diagnosed to have

cryptosporidiosis. Normally, in North Cumbria, all such cases would have been routinely investigated by

the Environmental Health Officers to find out where the infection might have come from and to give

advice.

From 1 March 1996, we are looking into such infections more closely and scientifically and to examine

whether there may be links between the cases in Copeland and Allerdale.

We have appointed a Research Assistant to carry out interviews of all such cases at home. The Research

Assistant will be in touch with you shortly to arrange a suitable time to talk to you. The interview will

take about 20 minutes. The Research Assistant will give you more details about the study and will also

be able to answer any questions you may have.

Any information given will be treated in the strictest confidence. The results will be published in

combined from, which means that no individual can be identified. The study has been approved by the

proper Ethics Committees.

Cryptosporidium is a parasite, that is commonly present in certain animals and can cause acute

gastroenteritis. It can be transmitted from one person to another, from animal to humans, or through

contaminated water, milk or some foods. People with low immunity and children aged 1 - 5 years are

most at risk from the infection.

This study will help us to look in detail at possible associations with different factors. This will be

particularly important in the prevention of infections due to this germ. Your GP has been informed about

the study.

We would be most grateful for your help in answering some questions. If you have any queries, the

Research Assistant, Mr Anthony Pennington may be able to help, at Copeland Borough Council,

telephone number 01946 852619 (during office hours).

Yours faithfully

Dr S K Goh

Consultant

North Cumbria Cryptosporidiosis Research Group


Appendices - Letters

247


CA1 2SE

Tel: 01228 603500Fax: 01228 603612


Dear Sir/Madam

CRYPTOSPORIDIOSIS STUDY IN COPELAND AND ALLERDALE

From 1 March 1996, a detailed scientific study will take place in Copeland and Allerdale into a parasite

called cryptosporidium. Cryptosporidium is commonly found in cattle, sheep and some other animals. In

humans, it can cause acute gastroenteritis symptoms. Although the symptoms are generally self-limiting,

they can be unpleasant and can be prolonged in individuals with low immunity.

This research study will aim to find out if there is a common link between the cases in Allerdale and

Copeland. The information obtained from all the cases will be compared with information from well

people living in the same area. This will allow study in detail and scientifically into possible

associations. The germ can be transmitted directly from animals to humans, from one person to another

or through contaminated water, milk or some foods.

We shall be most grateful for your help in this important study. You have been randomly chosen from

the computer holding the GP list, as a person, who is well and does not have symptoms, whose responses

could be compared with a person who is unwell with the germ.

We have appointed a Research Assistant to carry out interviews at home. Participation is entirely

voluntary and means answering some questions for about 15-20 minutes. Any information given will be

treated in strict confidence. The results, when published, will be in a combined form, which means

individuals cannot be identified. The results will certainly help in preventing infections due to this germ.

This study has been approved by the Ethics of Research Committees in the district.

The Research Assistant will be in touch, and will also be able to answer any queries you may have. We

do appreciate your help. The Research Assistant, Mr Anthony Pennington, is based at Copeland Borough

Council, telephone number 01946 852619 (during office hours).

Yours faithfully

Dr S K Goh

Consultant

North Cumbria Cryptosporidiosis Research Group

phmtyp/sg/crptodoc


Appendices - Letters to G P’s

248


Appendices - Summarised Protocol

249


Appendices - Summarised Protocol

250


Appendices - Questions & Answers Leaflet 1996/7

251


Appendices - Questions & Answers Leaflet 1996/7

252


Appendices - Letters to G P’s

253


Appendices - Letters to GP’s

254

Direct Dial : (01228) 603500

Our Ref: phmtyp/SG/CLA/GPs re crypto study

13 March 2001

To: All General Practitioners in Allerdale and Copeland (and Dalston and Caldbeck)

Physicians and Paediatricians, Cumberland Infirmary and West Cumberland Hospital

Dear Doctor

Sporadic Cryptosporidiosis Study in Allerdale and Copeland (March 1996 onwards)

You may recall previous information about the above study. This prospective case-control study

started in March 1996 initially for 16 months. However, there were insufficient numbers of cases at

the end of the study period and funding was obtained to continue for a longer period. The

completion date is now August 2002. The Ethical Committees have given their approval.

The study is a joint one between the Health Authority, the Local Authorities of Allerdale and

Copeland and the Communicable Disease Surveillance Centre in London.

The prospective case control study started initially because of the observed increase in number of

sporadic cases in Allerdale and Copeland in 1994 and 1995. Studying cases over a longer period

will include more cases which will be important in achieving more definitive results. It will also

help us see if there is a variation in the patterns of incidence over time and if there are common links

in the study area. The study results will be analysed and collated in August 2002 and will be

published when completed.

Recently a replacement Research Assistant has been appointed. He is Anthony Pennington and will

be based at Copeland Borough Council.

Thank you for your continued co-operation and support for the study. I enclose the leaflet used in the

study.

Yours sincerely

Dr S K Goh

Honorary Consultant

Chair, North Cumbria Cryptosporidiosis Steering Group


CA1 2SE

Tel: 01228 603500Fax: 01228 603612



Appendices - Press Release

255



256



257

PRESS RELEASE

JOINT PRESS RELEASE BY NORTH CUMBRIA HEALTH AUTHORITY, ALLERDALE

BOROUGH COUNCIL, COPELAND BOROUGH COUNCIL

UPDATE ON THE COLLABORATIVE STUDY ON CRYPTOSPORIDIOSIS

A "TUMMY" BUG

On 4 March 1996, a special collaborative study between the North Cumbria Health Authority, Allerdale Borough Council and Copeland Borough Council was launched. This was to gather information on cases of Cryptosporidiosis, a "Tummy" infection which causes unpleasant diarrhoea, sometimes accompanied by stomach pain, vomiting and fever. This was a positive and direct response to the observation that in 1994 and 1995, there was a higher rate of infection in Allerdale and Copeland, when compared with nearby Carlisle City/Eden. There were no major outbreaks of the disease in 1994 and 1995 and our routine investigations did not reveal any common links between cases. The collaborative study was scheduled to complete by the end of September 1997. However, by September 1997 the number of cases co-opted to the study (43) was much reduced than expected for the period of March 1996 to September 1997. None of these cases were connected. This means that we were unable to identify causes of the germ. This is a prospective (forward) study, which means that we cannot predict the numbers of cases that will actually occur. There is no known explanation to the lower than expected numbers in this study. Funding had been available for the study period March 1996 to September 1997. The Research Worker that was appointed to conduct the investigations has completed her task. All the three partners in this study feel that this investigation is important and would like to see this study continue so that we can include more cases to the study and identify possible link/s to the cases. This will mean identifying resources to enable this to happen.

ENDS

Note for Editors

Previous Press Release 4 March 1996 For further information please contact: Dr Stella Goh, Consultant in Communicable Disease Control North Cumbria Health Authority Phone: 01228 603500 26 January 1998


Appendices - Interview Protocol

258

Interview protocol Date: 3rd March 2000

Cases

Contact procedureNorth Cumbria Health Authority (NCHA)notifies the Research Assistant (RA) or therelevant Local Authority (LA), in the RA’sabsence of the case and their personal details.

1st attempt to contact the caseA standard case letter is sent to each caseexplaining that they have been diagnosed assuffering from cryptosporidiosis and askingthem if they are willing to participate in thecryptosporidiosis case-control study at thesuggested time on the enclosed appointmentslip. The RA or interviewer will automaticallyvisit the case in their home at the time statedon the appointment slip, unless they haveheard to the contrary from the case. The onusis on the case to contact the RA if the timestated on the appointment slip is notconvenient. If the RA does not hear from thecase, she will assume that the time stated isconvenient to call on them.

Non respondersIf there is no answer when the RA visits thecase at home, a no answer slip is postedthrough the door, asking them to contact theRA to arrange another appointment.

2nd attempt to contact the caseThe same day as the missed appointment, thecase is again sent the standard case letter withanother suggested time on the enclosedappointment slip. The RA will automaticallyvisit the case at home at the time stated on theappointment slip unless they have heard tothe contrary from the case.

Non respondersSee above.

3rd attempt to contact the caseIf after two failed attempts to contact the case,the RA asks an Environmental Health Officer(EHO) from the LA concerned to contact thecase’s GP, to obtain the case’s home telephonenumber and they then attempt to arrange anappointment on the RA’s behalf.

Interview procedurePrior to the interview taking placeWhen arriving at the case’s house, the RAintroduces herself and before beginning theinterview explains to the case/ case’s parent orguardian*, that after the questionnaire hasbeen administered, they will be handed aninformation sheet and that they will berequired to complete a consent form (agreeingto their participation in the study). The RAalso explains that she will be available toanswer any questions that they might haveregarding the study or the illness at the sametime.*Interviewees (both cases and controls) under18 years of age are always interviewed in thepresence of a parent or guardian, or with theparent or guardian’ consent, if they do notwish to be present. When the interviewee isunder 18 years of age, it is advantageous ifthey are present at the interview, althoughtheir presence can not be guaranteed.

During the interview procedureThe RA asks the questions in a straightfor-ward, matter of fact manner, following therecommendations outlined in the ‘Thirdreport of the group of experts onCryptosporidium’, and does not attempt toexplain or elaborate the questions asked otherthan the examples given in the questionnaire(if required). For example, Question 21 - Didyou have any other contact with fresh water(e.g. other water sports, fishing)?


Appendices - Interview Protocol

259

After the interview took placeThe interviewee is handed the informationsheet and requested to fill in the consentform. Only now does the RA really engage inconversation with the case and before leavingthe interviewee is thanked for their time andinterest in the study.

ControlsOnce the case has been notified to theresearch assistant by NCHA, NCHA thengenerates a list of 10 controls based on thecase’s age and postcode.

Contact procedureContacting controlsA standard control letter is sent to at least 3controls on the list explaining the nature ofthe study and asking them if they are willingto participate in the cryptosporidiosis case-control study at the suggested time on theenclosed appointment slip. Occasionally,more than 3 controls are contacted at onetime due to time constraints or previousdifficulties in obtaining the required numberof controls with that particular postcode. TheRA does not contact the controls by phone.Although, some of the relevant EHO’s find iteasier to contact the controls by phone, toarrange the appointment and then they sendthe letter and the appointment slip to confirmthe date and time. Like the cases, the RA orinterviewer will automatically visit the case intheir home at the time stated on theappointment slip, unless they have heard tothe contrary from the control.

Non respondersIf there is no answer when the RA visits thecontrol at home, a no answer slip is postedthrough their door asking them to contact theRA to arrange another appointment if theystill wish to participate in the study.Although, unlike the cases, if the control doesnot respond to the first letter, no more letters

are sent and no further attempts are madecontact the control. Instead another controlon the list is selected and contacted (using thesame procedure) in their place.

Interview procedureThe controls follow the same interviewprocedure as the cases (questionnaire,information sheet and consent form) and theyare also checked against the control criteria asper study protocol to ensure that they can beincluded in the study

Required number of controlsOnce 3 controls are obtained for eachincluded case, no more controls are contactedfrom the original list generated by NCHA.

Caseless controlsSome controls are contacted and theappointments arranged before the case hasbeen interviewed. If the case is subsequentlyexcluded from analysis in the study, thecorresponding controls will either becancelled if there is sufficient notice so as notto cause any further inconvenience orinterviewed and included in the study whenthere is insufficient time to cancel them.All cancellations made by the RA in this wayare done by post with a message urging themto contact the RA if they have any questionsrelating to the study which they would haveasked when the RA when she visited.


Appendices - Abbreviations

260

Abbreviations

CCDC Consultant in Communicable Disease Control

CDSC Communicable Disease Surveillance Centre

CI Confidence Intervals

CRU Cryptosporidium Reference Unit

DEFRA Department of Environment, Food and Rural Affairs

DMA District Meter Area (part of Water Supply Zone)

DoH Department of Health

DWI Drinking Water Inspectorate

EHO Environment Health Officer

GIS Geographical Information System

GP General Practitioner

NCHA North Cumbria Health Authority

PHL Public Health Laboratory

PHLS Public Health Laboratory Service

RA Research Assistant

UK United Kingdom

UKWIR United Kingdom Water Industry Research Limited

USA United States of America

VLA Veterinary Laboratories Agency (DEFRA)

WSZ Water Supply Zone

WTW Water Treatment Works

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