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Willem Takken

Laboratorium voor Entomologie

Wageningen Universiteit en Research Centre

FACTORS THAT DETERMINE THE RISK OF VECTOR-BORNE DISEASE OUTBREAKS IN THE

NETHERLANDS

DO WE NEED TO WORRY?

The approximate sequence of spread of bubonic plague (The Black Death) in Europe, between its entry from Asia in 1346 and its eventual spread, via the Baltic region, into Russia in 1348.Around one-third of the European population perished.

Plague

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Published: 1994

sleeping sickness

malariadengue

plague

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Lyme disease

Bluetongue

Human vector-borne diseases in EuropeMalariaPlagueLeishmaniasisYellow feverWest Nile virusChikungunya virus**TyphusLyme borreliosisTick-borne encephalitisHuman granular ehrlichiosisRickettsiae feversBartonella

** first time in Europe in 2007

MosquitoesFleasSandfliesMosquitoesMosquitoesMosquitoesBody liceTicksTicksTicksTicksBody lice

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Animal Vector-borne diseases in Europe

BluetongueAfrican horse sicknessAfrican swine feverTheileriaBabesiaLyme borreliosisOnchocerciasisWest Nile virus

Biting midgesBiting midgesBiting midgesTicksTicksTicksBlackfliesMosquitoes

Anti-biotics for affected animals

commonSouthern Europe, Africa

Dermacentorreticulatus

Babesiosis

??????North AfricaCulicoides spp.African horse fever

????????? (Spain)Culicoides spp.African swine fever

vaccinationemergingMediterranean countries

Culicoides obsoletus spp.Bluetongue

???commonScandinavia, FranceCulicidae spp.Ockelbo disease

No (vaccine development in progress)

rare (1996, 1999, 2003, 2004)

Southern/Eastern EuropeCulex pipiens et al.West Nile

Prevention of tick bites, anti-biotics

common, emergingEurope, N. AfricaIxodes ricinusLyme disease

???emergingWestern EuropeIxodes ricinusRickettsiosis

VaccinationcommonCentral and Northern EuropeIxodes ricinusTick-borne

encephalitis

Treatment of infected hostscommonMediterranean

countries

Sandfly(Phlebotomusspp.)

Leishmaniasis

Control possible?Occurrence in EuropeDistributionVector speciesDisease

POTENTIAL VECTOR-BORNE DISEASES IN THE NETHERLANDS

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MALARIA

malaria parasites in red blood cells

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Summer

Winter

Spring

Disease outbreak

Anopheles atroparvus: 3 generations per year, overwintering as adult

Autumn

Malaria infection

Malaria in the Netherlands

Malaria in Wormerveer

1902 - 1920

Nikolaas SwellengrebelA – Malaria houseB – Infected mosquitoC – Heavily infected house

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1944: Introduction of DDT

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Drugs and bednets

1932BrazilWest AfricaMalaria mosquito

???North-EuropeSouth-EuropeDermacentorreticulatus

1930North AmericaSouth AmericaFire ant

1998South-EuropeTropical AfricaBluetongue vector

1986Americas, Africa, Europe

S.E. AsiaAsian tiger mosquito

When?Invaded regionOriginSpecies

Invasion of disease vectors and pests

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1986AmericasDengue Asian tiger mosquito

1999North AmericaWest Nile virusCulex pipiens

???North-EuropeBabesiosisDermacentorreticulatus

2006North EuropeBluetongueBluetongue vector

2007ItalyChikungunyaAsian tiger mosquito

When?Invaded regionDiseaseSpecies

Invasion of diseases

Bluetongue

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Bluetongue in Europe, status December 2007

2006

Bluetongue in Europe, October 2008

Oct. 2008: BTV6

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West Nile virus USA – 1999-2007

Bron: CDC 2008

1999

2007

Humane gevallen van West Nile virus, VS

1

10

100

1,000

10,000

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Log

cas

es a

nd d

eath

s

cases

deaths

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2005

WNV WNV

WNV

WNV

2004

2004

Aedes albopictus: dengue vector

West Nile virus outbreaks

2007: Chikungunya

Aedes albopictus introductions

17 companies

Lucky bamboo

2005, 2006, 2007

Aedes albopictus

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0

20

40

60

80

100

120

140

160

180

200

27-30 31-34 35-38 39-42 43-46 47- 50 51-2 3-6 7-10 11-14 15-18 19-22 23-26 time (w eek nrs)

cum

ulat

ive

num

ber o

f col

lect

ed

Ae.

alb

opic

tus

of a

ll co

mpa

nies

(gre

y ba

rs)

0

2

4

6

8

10

12

num

ber o

f Luc

ky b

ambo

o-im

port

ing

com

pani

es p

ositi

ve

for

Ae.

alb

opic

tus

(bla

ck b

ars)

# Ae. albopictus

# infested companies

Total number of Ae. albopictus collected over time and number of companies affected (source: Scholte et al., In Press)

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Lyme disease

Increase in incidence of Lyme disease, 1994-2005

Source: RIVM 2006

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Selfregistration of tick bites via Natuurkalenderhttp://www.natuurkalender.nl/index.asp

Variation in tick populations and Borrelia infections

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

Jul-0

6A

ug-0

6S

ep-0

6O

ct-0

6N

ov-0

6D

ec-0

6Ja

n-07

Feb-

07M

ar-0

7A

pr-0

7M

ay-0

7Ju

n-07

Jul-0

7A

ug-0

7S

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7O

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n-08

Feb-

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Jul-0

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8

Perc

enta

ge B

orre

lia in

fect

ions

0.1

1.0

10.0

100.0

Mea

n no

. of n

ymph

s pe

r 200

sqm

% infected

mean no. nymphs/site

0-36.40-28.50-38.50-100-200-33.30-250-300-8.30.000-1000-400-46.6range of infections

20.019.611.42.95.311.17.06.11.30.028.918.819.8% infected

13722031374.003312138842520422129178466Nymphs

Nov-08

Sep-08Jul-08May-

08Mar-08

Jan-08

Nov-07

Sep-07

Jul-07

May-07

Mar-07

Jan-07

Nov-06

Sep-06Jul-06

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Upper temperature limits for establishment of Ixodes scapularis in Canada (source: Int J Parasitol 2006;36: 63–70)

Oak processionary caterpillar

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Eradicated:

Pest, Typhus, Yellow fever, Malaria, Dengue

Present:

TBE, Leishmaniasis, Ockelbo disease, Theileria, Babesia

(cattle), Onchocerca(cattle)

New:Bluetongue, African

horse sickness, West Nile virus,

Chikungunya

Possible:

Dengue, other arboviruses, CCH fever,

Babesia, Bartonella, Rift Valley fever

Emerging:

Lyme borreliosis, Anaplasma, Rickettsia

Vectorborne diseases in Europe

Emerging infectious diseases (Nature, 2004)

2005Chikungunya fever

2006Bluetongue virus

2007Chikungunya fever2007

Leishmaniasis

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Rising temperatures favourable for arthropods and parasite and pathogen development

Conclusions (1)

− Vector-borne diseases are “emerging” throughout the world

Reasons:

Trade, international travel, environmental change(deforestation, irrigation, urbanisation, nature conservation)

− Surveillance inadequately organised

− Control strategies poorly developed

− Growing poverty in many countries remains an important reason for the maintenance of vector-borne diseases

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Conclusions (2)

− Several vector-borne diseases and pests appear associatedwith climate change;

− Higher temperatures favourable for poikilothermicorganisms;

− Higher temperatures favour pathogen development in arthropods (e.g. tick-borne encephalitis; Chikungunya; dengue; Rift Valley fever; West Nile virus)

− Need for risk assessment by modeling of vector-bornedisease under climate scenario’s, Early warning studies;

− Need for laboratory studies of vectors and vector-pathogencomplex for model verification;

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THANK YOU