Aquaculture Health Magazine

AQUACULTUREHEALTHI N T E R N A T I O N A L

ISSUE 1 MAY 2005 $10.00

2 AQUACULTURE HEALTH INTERNATIONAL MAY 2005

4 EDITORIALDr Scott Peddie outlines the scope of this new publication

5 AQUATIC ANIMAL DISEASES AND THEIR ECONOMIC IMPACT:A global perspective

6 DIAGNOSTIC LABORATORY SERIES:Aquatic Diagnostic Services at the Atlantic Veterinary College,Prince Edward Island, Canada

9 NEWSUpdates from around the globe

10 FORTHCOMING CONFERENCES & MEETINGSA look at whats coming up

11 COMPANY FOCUS:Schering-Plough Aquaculture

12 FOCUS ON SHELLFISH:Bonamia - uncovering microcell secrets

14 FOCUS ON FINFISH:An overview of salmonid rickettsial septicaemia

EDITORIAL DIRECTOR:Dr Scott Peddie

PUBLISHER: Keith Ingram

MANAGER: Vivienne Ingram

ASSISTANT EDITOR: Mark Barratt-Boyes

CONTRIBUTORS:Dr Melba G Bondad-Reantaso

Dr Rohana P SubasingheDr Dave Groman

Dr Franck BertheDr Ben DigglesDr Oscar Parra

Dr Sergio VasquezDr William J Enright

DESIGNER: Rachel Walker

PRE PRESS/CTP: BPG Digital

PRINTERS: Business Print Group

WEBSITE: Web4U

An informative journal for theaquaculture health professional

Published by:VIP PUBLICATIONS LTD4 Prince Regent Drive,

Half Moon Bay, Auckland 1706,New Zealand

Ph 0064 9 533 4336 Fax 064 9 533 4337email [email protected]

www.aquaculturehealth.com

General: Reproduction of articles and materials published in Aquaculture Health International in whole or part, is permitted provided the source and author(s) areacknowledged. However, all photographic material is copyright and written permission to reproduce in any shape or form is required. Contributions of a naturerelevant to the aquaculture industry are welcomed and industry participants are especially encouraged to contribute. Articles and information printed inAquaculture Health International do not necessarily reflect the opinions or formal position or the publishers unless otherwise indicated. All materialpublished in Aquaculture Health International is done so with all due care as regards to accuracy and factual content, however, the publishers cannot acceptresponsibility for any errors and omissions which may occur. Aquaculture Health International is produced quarterly.

ISSN 1176-86330 ISSN (web) 1176-8649

CONTENTS Issue 1, May 2005

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SCHERING-PLOUGH AQUACULTUREAquaculture Centre, 24-26 Gold Street

Saffron Walden, Essex CB10 1EJ, UKTelephone 44 (0) 1799 528167Facsimile 44 (0) 1799 525546

SCHERING-PLOUGH ANIMAL HEALTH CORPORATION

PO Box 3182, Union New Jersey 07083-1982, USA

Telephone +1 908 629 3344Facsimile +1 908 629 3365

www. spaquaculture.com

FROM THE COVER

MAY 2005 AQUACULTURE HEALTH INTERNATIONAL 3

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Welcome to the first issue of Aquaculture HealthInternational! In todays world, aquatic livestock healthand welfare is becoming a key issue of interest to anincreasingly diverse audience. Fish health professionals, fish farmers,policy makers, legislators and non-governmental organisations areall key stakeholders in the aquaculture health arena.

Here at Aquaculture Health International we have identified aneed for a fish and shellfish health publication that is widelyavailable to such an audience, communicating information in aneasily accessible format. The aim of Aquaculture HealthInternational is to be a publication broad in appeal and style, andwith a cutting-edge content.

That livestock health is a topic of truly global significance iseloquently outlined in the article by Melba Bondad-Reantaso andRohana Subasinghe of the FAO on Aquatic Animal Diseases andtheir Economic Impact: a global perspective. Not only is diseaseresponsible for huge economic losses to businesses andcommunities in some of the most economically vulnerable areas ofthe planet, it has implications for international trade and trans-boundary movements of livestock.

Subsequent articles deal with a widerange of topical health and welfarequestions such bonamia in shellfish andSalmonid Rickettsial Septicaemia incultured salmon. We are also privileged tohave on board Drs David Groman andFranck Berthe of the Atlantic VeterinaryCollege, University of Prince EdwardIsland to produce and edit our series on the services offered bydiagnostic laboratories throughout the world. Dr Ben Diggles ofDigsFish Services Pty Ltd will be another regular contributor,providing us with an Australasian perspective.

The international flavour of the magazine is reflected in thecontributors who have given their time and expertise to puttogether the first issue of this magazine - thank you! We alsoextend our thanks to the advertisers who have contributed to thisissue, and to Invest Northern Ireland for their financial support.

Finally, we are constantly on the lookout for news items andarticle ideas from your part of the world. So please do not hesitateto get in touch with us if you wish to contribute to future issues.

DR SCOTT PEDDIE, EDITORIAL DIRECTOR

AQUACULTURE HEALTH HASGLOBAL SIGNIFICANCE

VIP Publications Limited is proud to join forces with ScottPeddie of Patterson Peddie Consulting Limited to bring youthis first issue of Aquaculture Health International.The aquaculture industry is often ignored by other primary

producers and governments as an important food producer.Yet this industry is able to produce an economical quality

source of fresh seafood for world consumption, where otherprimary producers are struggling to maintain growth in theface of increasing costs, climatic conditions and loss ofagricultural space.

The aquaculture industry worldwide isshaping itself to meet these future demands.To ensure that the industry remains healthyand disease-free will require the support ofboth marine scientists and aquaculturehealth professionals in the future.

As publishers of the professional marine publicationsProfessional Skipper, NZ Workboat Review and NZ Aquaculture, weare proud to support this sector of our industry, and hope youenjoy this first edition.

FROM THE PUBLISHERKEITH INGRAM, PUBLISHER

POST TO: VIP Publications Ltd, 4 Prince Regent Drive, Half Moon Bay, Auckland 1706, New Zealand GST No: 68-684-757

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With an average annual growth rate of 8.9 percent since1970, aquaculture is now considered to be the fastestgrowing food-producing sector in the world. Bycomparison, the average annual growth rate for capturefisheries was only 1.2 percent, and for terrestrial farmed meatproduction systems only 2.8 percent, over the same period.

In 2002, the total world aquaculture production (includingaquatic plants) was reported to be 51.4 million tonnes byvolume and US$60 billion by value. This represents an annualincrease of 6.1 percent in volume and 2.9 percent in value,respectively, over reported figures for 2000. Asia produced 91.2percent (by volume) and 82 percent (by value) of globalaquaculture production.

DISEASE AS A PRIMARY CONSTRAINTLike other farming systems, the aquaculture industry has beenoverwhelmed with a fair share of trans-boundary aquatic animaldiseases caused by viruses, bacteria, fungi, parasites and otherundiagnosed and emerging pathogens. Disease has thus become aprimary constraint to the culture of many aquatic species,impeding both economic and social development in manycountries. This situation can be attributed to a variety of multi-faceted and highly interconnected factors, such as: the increased globalisation of trade in live aquatic animals and

their products the intensification of aquaculture through the translocation of

broodstock, postlarvae, fry and fingerlings the introduction of new species for aquaculture and fisheries

enhancement the development and expansion of the ornamental fish trade the enhancement of marine and coastal areas through stocking

aquatic animals raised in hatcheries unanticipated negative interactions between cultured and wild

fish populations poor or effective biosecurity measures slow awareness on emerging diseases the misunderstanding and misuse of specific pathogen-free

(SPF) stocks (eg shrimps) climate change, and all other human mediated movements of aquaculture

commodities.

SOCIO-ECONOMIC IMPACTSThe frequency of occurrence and the magnitude of spread andeffects have prompted many countries to provide estimates ofdisease impacts. Although very much a grey area in the scientificliterature, the impacts of disease have been estimated in socio-economic terms (eg losses in production, income, employment,market access or market share, investment and consumerconfidence; food shortages, industry failure or closure of businessor industry).

ADB/NACA (1991) reported that the minimum, conservativelyestimated lost farm production in 1990 to fish diseases such as

epizootic ulcerative syndrome of fresh and brackish water fishes,penaeid shrimp diseases and a variety of other diseases causinglosses in freshwater finfish pond culture and marine cage culturein 15 developing Asian countries was US$1.36 million.

At the global level, combined estimated losses in productionvalue due to shrimp diseases from 11 countries from 1987 to 1994were about $3.01 billion.

At the national level, some estimates of the economic impact ofkey diseases are: Infectious salmon anaemia cost the Scottish farming industry

20 million in the 1998/1999 outbreak, and resulted in acontinued annual cost to the Norwegian and Canadianindustries of US$11 and $14 million, respectively.

In Thailand, losses due to yellowhead disease and white spotdisease of shrimp were estimated at $650 million.

Losses from suspected koi herpes virus in Indonesia amountedto $15 million.

In New South Wales, Australia, some $30 million worth ofproduction was lost due to a single pathogen of rock oyster,Marteilia sydneyi, or QX disease.

Abalone mortalities in Taiwan in 2003 cost the domesticabalone industry $11.5 million.Economic impacts have also been expressed in terms of the cost

of investment in disease research and control and other healthmanagement programmes. Some examples from around theworld are: The aquatic animal health research budget for China, Thailand

and Norway is around $6, $5 and $50 million, respectively. Australias national plan on aquatic animal health, known as

Aquaplan, costs over $4 million for development and initialyears of implementation.

The United States has budgeted $375,000 per year to develop anational aquatic animal health plan.

Norway spends more than $77 million for overall managementof fish diseases covering such aspects as legislation and supportto surveillance and control programmes.


AQUATIC ANIMAL DISEASES AND THEIR ECONOMIC IMPACT: A global perspectiveBY DR MELBA G BONDAD-REANTASO AND DR ROHANA P SUBASINGHE(FOOD AND AGRICULTURE ORGANISATION OF THE UNITED NATIONS, ITALY)

MICROSCOPIC SECTION OFA GILL INFECTED WITH KHV,DEPICTING INTRANUCLEAR

FUSION (SEE ARROW)Picture courtesy

of Dr Ron Hedrick FRESHWATER FISH (CARP) INFECTED WITH KOI HERPES VIRUSPicture courtesy of Stuart Millar


Canada allocates $34 million for reactive disease control. China spends $73 million for disease control.

A recent report published by the Institute of Aquaculture inStirling estimated that private sector research and developmentinvestment in aquatic animal products is approximately $2.1 million(for antiparasitics) to $8.2 million (for antibiotics), with a globalmarket share worth $29.4 million and $274.4 million, respectively.

Figures remain high, a clear indication of the importance ofhealth management and investments which governments and theprivate sector is willing to spend to counter production losses.

AGREEMENTS AND INSTRUMENTS ON AQUATIC ANIMAL HEALTHA number of regional and global instruments exist, eithervoluntary or obligatory, wholly or partly, which aim to providecertain levels of protection in order to minimise the risks ofpathogen/disease incursions associated with the internationaltrade of aquatic animals and their products. (Table 1)

In the Asia-Pacific region, national strategies on aquatic animalhealth are either in the process of development or at the initialstages of implementation as part of the implementation of theAsia TGBCIS. These strategies, which contain the action plans ofgovernment for the short, medium and long term, follow theconcept of phased implementation based on national needs.

The National Strategy framework includes important elementssuch as national coordination, legislation and policy, list ofpathogens, institutional resources, diagnostics, health certificationand quarantine, surveillance and reporting, disease zoning,contingency planning and emergency response, import risk analysis,quality assurance/quality control, research and development,capacity building, awareness building and communication,farmer/private sector involvement, financial resources, monitoringand evaluation and regional/international cooperation.

Australia has implemented its Aquaplan from 1998 to 2003, andis now on its second five-year implementation, while Canada andthe United States are in the process of finalising their nationalaquatic animal health plans.

DEMAND FOR IMPROVED AQUATIC ANIMAL BIOSECURITYAquatic animal health management has recently assumed highpriority in many aquaculture-producing regions of the world.

Serious socio-economic losses, environmental impacts and thecosts involved in disease prevention, containment, eradicationand management has stimulated many countries to improve theirlaboratory facilities and diagnostic expertise, and advancetechnologies on disease control and therapeutic strategies inorder to handle disease outbreaks more effectively.

There has also been some progress in dealing with aquaticanimal disease problems in terms of better understanding ofrisks, increasing awareness, creating effective policy andlegislation, enhanced research and manpower development andsome capacity to respond to disease emergencies.

There has also been intensified regional and internationalcooperation, increased networking and better links betweenvarious stakeholders, such as fisheries and veterinary authoritiesand the private sector. However, all these need to be furtherenhanced in order to match the needs of the rapidly developingaquaculture sector.

Resource protection (aquaculture, wild fisheries and the generalenvironment), food security, trade, consumer preference for highquality and safe products, production profitability, investmentand development issues, and new threats of emerging healthproblems are some of the multiple objectives that willpersistently drive the growing demand for aquatic animalbiosecurity.

Effective compliance with regionally and internationally agreedinstruments, and focussing efforts on prevention, bettermanagement practices and maintaining healthy fish may be moreimportant than focussing on why fish get sick. Improvingbiosecurity, applying risk analysis and using epidemiologicalapproaches will be important tools for disease prevention,control and management.

Health management is a shared responsibility, and eachstakeholders contribution is essential to the health managementprocess.

ACKNOWLEDGEMENTSWe would like to acknowledge the following people whoprovided valuable data, especially on economic investments indisease management. Drs Kevin Amos and Jill Roland (UnitedStates), Dr Eva-Maria Bernoth (Australia), Dr Supranee Chinabut(Thailand), Professor Tore Hastein (Norway), Dr SharonMcGladdery (Canada), Dr Zilong Tan (Singapore) and DrQingyin Wang (China).

FURTHER READINGBondad-Reantaso MG, Subasinghe RP, Arthur JR, Ogawa K,Chinabut S, Adlard R, Tan Z and Shariff M. 2005. Disease andhealth management in Asian aquaculture (keynote address).Special issue of Veterinary Parasitology in conjunction with the2005 World Association for the Advancement of VeterinaryParasitology. October 2005, Christchurch, New Zealand. (inpress).Arthur JR and Bondad-Reantaso MG (eds.). Capacity andawareness building on import risk analysis for aquatic animals.Proceedings of the workshop held April 1-6, 2002 in Bangkok,Thailand and August 12-17, 2002 in Mazatlan, Mexico. APECFWG 01/2002. Bangkok, Thailand. Network of AquacultureCentres in Asia-Pacific (NACA). pp 203 (See www.enaca.org).Subasinghe RP, Bondad-Reantaso MG and McGladdery SE.2001. Aquaculture development, health and wealth. In RPSubasinghe, P Bueno, MJ Phillips, C Hough, SE McGladdery and JR Arthur. (eds.) Aquaculture in the Third Millennium.Technical Proceedings of the Conference on Aquaculture in the Third Millennium, Bangkok, Thailand, February 20-25,2000.See www.fao.org/DOCREP/003/AB412E/ab412309.htm

BINDING

Agreement on the Application of Sanitary and PhytosanitaryMeasures (SPS Agreement)(WTO)

Aquatic Animal Health Code(OIE, World Organisation forAnimal Health)

Convention on BiologicalDiversity (CBD) and theCartagena Protocol on Biosafety(UNEP)

Convention on InternationalTrade in Endangered Species(CITES)

European Union (EU) relatedlegislation and directives

NON-BINDING

ICES Code of Practice on theIntroductions and Transfers ofMarine Organisms

EIFAC Codes of Practice andManual of Procedures forConsideration of Introductionsand Transfers of Marine andFreshwater Organisms

Asia Regional TechnicalGuidelines on HealthManagement for the ResponsibleMovement of Live AquaticAnimals and the BeijingConsensus and ImplementationStrategy (Asia TBGCIS).

FAOs Code of Conduct forResponsible Fisheries (CCRF)

TABLE 1. Important treaties and agreements related tointernational trade in aquatic organisms and their products

Avariety of service, research and teaching laboratories existworldwide which support the aquaculture industry. Theselaboratories often offer disease screening and diagnosticservices, with various levels of testing and quality assurance. Inaddition, some laboratories may not engage in pro-activeinternational marketing. As a result, many aquaculture companiesand their fish health service providers are not always aware of therange of laboratory resources available in the global marketplace.

This series of laboratory articles will provide Aquaculture HealthInternational readers with a guide to diagnostic laboratories whichoffer regional, national or global routine - fee for serviceveterinary diagnostic services to finfish, mollusc and crustaceanproducers and their veterinary service providers.

In addition, the articles will focus on affiliations that thesediagnostic laboratories may have with universities, governmentagencies and institutes linked to aquatic health training orresearch. The article will seek input from each laboratory as totheir strategic goals and operational philosophy.

This objective services review, in combination with subjectiveinput on management philosophy, will provide readers with a

balanced description of the laboratory, and will ultimately helpaquaculture veterinary professionals to make informed decisionson selecting appropriate diagnostic service laboratories, aquatichealth training and research programmes.

To accomplish this, we will provide a formative review of theservices provided by each laboratory, with the approval andassistance of the company, programme or laboratory management.To this end, we have developed an aquatic health diagnosticservices evaluation checklist which will detail information on thetype and scope of services offered: quality assurance programmes referral options reporting methods client base, and the cost of testing.

We will strive to capture a thorough description of the diagnosticcomponent of the laboratory, with a capsulated summary ofservices provided. If a laboratory prefers not to participate in theseries, we will only provide a description based on publishedinformation, public advertising or government documentation.


DIAGNOSTICLABORATORY SERIESBY DR DAVE GROMAN AND DR FRANCK BERTHE(ATLANTIC VETERINARY COLLEGE AT THE UNIVERSITY OF PRINCE EDWARD ISLAND, CANADA)

DIAGNOSTICSSince the inception of the Atlantic Veterinary College in 1986, theDiagnostic Services Unit of the college has provided a range ofdiagnostic and analytical testing to finfish farmers, shellfishgrowers and aquaculture veterinarians throughout Atlantic Canadaand worldwide.

The provision of a diagnostic service component as an integralpart of the AVC fish health programme is linked to the overallstrategic goals of the college: to provide a fish health programmeoffering aquatic veterinary training, continuing education, researchand service to the aquaculture industry in Atlantic Canada.

Initially, the range of diagnostic and clinical services offered to

FEATURED DIAGNOSTIC LABORATORY:Aquatic Diagnostic Services at the Atlantic Veterinary College (Canada)

veterinarians and fish farmers was provided to support theundergraduate teaching and research programmes at the AVC.With the growth of the regional finfish aquaculture industry in theearly 1990s, the college developed a business division, AquaticDiagnostic Services. ADS was subsequently formed in January1996 and remains as an integrated division of the DiagnosticServices Unit of the AVC at the University of Prince Edward Islandin Charlottetown, Prince Edward Island, Canada.

With the transfer from an academic to a more business-orientedfunction, services offered through ADS increased in diversity.Today ADS, in conjunction with the other service, research(CAHS) and continuing education units (CAI) of the college,offers a range of finfish, crustacean (LSC) and mollusc diagnostictesting, including gross and microscopic pathology, bacteriology,virology, parasitology, endocrinology, clinical pathology, toxicologyand consultation (TAS).

The ADS uses testing procedures based on recommendationsprovided by the Office International des Epizooties (OIE), theAmerican Fisheries Society and the Canadian Fish HealthProtection Regulation. ADS, through its direct affiliation withAVC-Diagnostic Services, participates in a ring-testing qualityassurance programme for veterinary diagnostic laboratories(VALQAP) which is operated by Diagnostic Chemical Ltd (DCL).The AVC was recently designated an International ReferenceLaboratory by the OIE for infectious salmon anaemia in NorthAmerica. It is only the second such laboratory in the world.

ADS clients have traditionally been located primarily in AtlanticCanada and British Columbia (more than 70 percent). But inrecent years the client base has expanded to include submissionsfrom Quebec, Ontario, the United States, Chile, Central America

FRANCK BERTHE (FAR LEFT) WITH STUDENTS AND STAFF AT ONE OF THE MULTI-HEADED MICROSCOPES IN DIAGNOSTIC SERVICES, ATLANTIC VETERINARYCOLLEGE, UNIVERSITY OF PRINCE EDWARD ISLAND


(Panama and Mexico) and Europe (primarily Greece andDenmark).

The bulk of our referral work, both regionally and worldwide, isinterpretative histopathology. ADS is currently developing andoffering testing in the emerging fields of immuno-cytochemistry,molecular diagnostics (in-situ hybridisation, RT-PCR and RealTime PCR) and product traceability, including antibiotics,pigments and feed additives.

It is expected that with these new tools ADS will be better able toserve clients worldwide. For routine interpretative diagnostictesting it is the policy of ADS and AVC-Diagnostic Services that allsamples be submitted through a veterinarian or veterinary clinic.ADS also provides diagnostic support to scientists and governmentfish health inspectors seeking specific testing as part of researchand surveillance.

The current fee structure for testing reflects full cost recoveryrelated to materials and operational overheads, and a surcharge forprofessional labour, ie the pathologists time. Testing offered byADS is not subsidised by provincial or federal governmentcontracts, and provides all clients with full confidentiality.

The service is integrated into the existing mammalian diagnosticunit. As a result, ADS utilises the expertise of 24 technical supportstaff, who handle finfish and shellfish submissions as well as thosefrom mammals and birds. AVC faculty and clinical professionalsassist with diagnostic interpretation on a case-by-case basis.

The ADS currently draws on the professional expertise of four fishpathologists and two field-based clinicians. Pathologists include: David Groman, section head for Aquatic Diagnostic Services

Gerald Johnson, Director of Diagnostic Services David Speare, professor of fish pathology, and Franck Berthe, Canada Research Chair in shellfish health.

They are all members of the Department of Pathology andMicrobiology at AVC. Finfish clinician Larry Hammell andshellfish clinician Jeff Davidson, who are both members of theDepartment of Health Management at AVC, also contribute todiagnostic case consultation.

The ability of Aquatic Diagnostic Services to access this widerange of expertise in fish pathology and clinical medicine providesaquaculture veterinarians and aquaculture clients with a fullyintegrated diagnostic service.

Aquatic health diagnostic services evaluation checklistThe following table summarises the level and diversity of aquatic diagnostic testing provided, as well as information onmethods of pathogen or agent confirmation, laboratory quality assurance, referral services, reporting options, clientbase and cost of testing. (See key below.)

CATEGORY

Fin-Fish NA NA S F S S S F F F S F F S S S

Mollusc S NA S F S S S F F F S S F S NA NA

Crustacean NA NA S F S S S F F F S S F S NA S

Pathogen ID M M M M M,C,I M,C M,C,I,G M,C AC IN AC,I

Quality Assurance IN IN IN,EX IN,EX IN, EX IN IN IN,EX IN,EX IN,EX IN,EX IN,EX IN IN,EX

Referral A A A A A A A A A A A A A A A

Reporting P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E P,F,E

Client Base R R,N,I R R,N,I R,N,I R,N,I R,N,I R,N,I R,N,I R,N,I R,N,I R,N,I R,N,I

Cost ( $ ) $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $

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KEYScope of testing Full testing available = F

Selective testing = SPathogen/agent ID By morphology = M

By culture = CBy immunology/serology = IBy genomic / molecular = GBy analytical chemistry = AC

Quality assurance scheme Internal quality control = INExternal quality assurance/ring testing = EXCertification = ISO

Referral testing Available = ANot available = NA

Reporting options By post = PBy fax = FBy email = EBy website = W

Client base Regional = RNational = NInternational = I

Cost of services Full cost recovery = $Partial subsidy = P$Full subsidy = F

MAP OF ATLANTIC CANADA SHOWING PRINCE EDWARD ISLAND IN YELLOW AT THE CENTRE


EDUCATION LINKSThe technical staff and clinical professionals working in theDiagnostic Services Unit at the AVC also play key roles in theclinical training of undergraduates, residents and graduatestudents. For example, fourth year undergraduates are offeredrotations in aquaculture diagnostics and on-farm clinical servicesof up to three weeks in length. Both courses utilise ADS andDiagnostic Services personnel and facilities. Recently, AVCannounced a Master of Veterinary Science degree which nowprovides graduate students with the opportunity to specialise inaquaculture medicine or fish pathology. It is anticipated that a fullresidency programme in aquatic animal health will be forthcomingin the near future.

Since AVC opened in 1986, continuing education in aquaticanimal health has been a significant focus. With the formation ofthe Canadian Aquaculture Institute in the mid-1990s, a moreformalised role for AVC faculty, clinical professionals andtechnologists has been developed in aquatic health. In particular,ADS pathologists and technologists have participated in numerousregional, national and international short courses.

Recent examples include: Aquatic Animal Health Subprogramme: training course on

exotic diseases of aquatic animals. Offered by the AustralianGovernment CSIRO Livestock Industries Department, and heldat the Australian Animal Health Laboratory in Geelong, Australiaduring March and April, 2004.

Care, Handling and Use of Aquatic Animals: Organised throughthe Canadian Aquaculture Institute and held at the University ofPrince Edward Island during August, 2004.

Shellfish Health and Disease: up-coming in June 2005. It is beingorganised through the Canadian Aquaculture Institute, and willbe held at the University of Prince Edward Island.

RESEARCH LINKSAquatic Diagnostic Services staff and clinical professionals haveparticipated in many applied research projects directed toward thedevelopment of new diagnostic tests and analyses in conjunctionwith both AVC/UPEI researchers and fish health colleaguesworldwide.

Examples include: the development of an ELISA for detecting antibodies in trout

and salmon to the ISA virus, and the identification of HPLC assays for tissue and sediment assays

of antibiotics (like OTC) and sea lice therapuetants (like SLICE -emamectin-benzoate ).Research collaboration occurs most often, however, when ADS

participates in both competitive government and private industry-funded grants or contracts. In this capacity, ADS generallyparticipates by providing diagnostic support to in-vivoexperiments with live fish, or as co-investigators in in-vitroexperiments.

Recent examples of joint projects funded through AQUANET(Canadas research network in aquaculture) include: The Biology, Pathogenesis and Epizootiology of Nodavirus

Strains Found in Atlantic cod (Gadus morhua) and haddock(Melanogrammus aeglefinus).

Advanced technology in diagnostics of economically significantmollusk infectious diseases for improved health management inCanada.

RELEVANT WEBSITES:AVC Atlantic Veterinary College - www.upei.ca/~avc/ ADS Aquatic Diagnostic Services - www.upei.ca/aquatic/DS AVC Diagnostic Services - www.upei.ca/~diagserv/CAHS Centre for Aquatic Health Sciences - www.upei.ca/~cahs/ LSC AVC Lobster Science Centre - www.lobsterscience.ca/TAS Toxicology & Analytic Services - www.upei.ca/~tas/CAI Canadian Aquaculture Institute - www.upei.ca/cai/UPEI University of Prince Edward Island - www.upei.ca/PEI Prince Edward Island - www.gov.pe.ca/ AFS American Fisheries Society -

www.fisheries.org/fhs/bb_inspection.htmFHPR Fish Health Protection Regulations -

www.pac.dfo-mpo.gc.ca/sci/aqua/pages/fhprot_e.htm OIE Office International des Epizooties -

www.oie.int/eng/normes/en_amanual.htmVLAQAP Veterinary Lab Assoc QA Programme -

www.upei.ca/~diagserv/quality.htmDCL Diagnostic Chemicals Ltd -

www.dclchem.com/veterinary/vla.html

CONTACT DETAILSAtlantic Veterinary College, University of Prince Edward Island550 University Avenue, Charlottetown, Prince Edward Island,Canada C1A 4P3. Telephone 902 566 09864, Fax 902 566 0723Email [email protected] Website www.upei.ca/aquatic/

DIAGNOSTIC LABORATORY SERIES

THE UNIVERSITY OF PRINCE EDWARD ISLAND WITH THE ATLANTIC VETERINARY COLLEGE IDENTIFIED AT THE FAR RIGHT


COMPANIES UNITE TO OFFER A FISH HEALTHECONOMICS SERVICEA United Kingdom aquaculture consultancy, Patterson PeddieConsulting Ltd, is to work with a Queensland-based healthconsultancy Digsfish Services Pty Ltd. They have united to offer afish health economics service to commercial farmers,pharmaceutical companies and government agencies in NewZealand, Australasia, the Pacific Islands and Asia. Theannouncement was made on March 30.

The managing director of Patterson Peddie Consulting, Dr ScottPeddie, says the health economics approach is used in two mainways: to assess the economic impact of disease at farm, regional,

national and international level, therefore helping decision-makers prioritise disease prevention and control strategies, and

to assess different control options and their financialimplications. By putting disease management at the centre of thebusiness planning process, it helps producers optimise returnsand reduce costs and risks where possible.We are already involved in developing consultancy services in

this area in the northern hemisphere, says Dr Peddie. Theprogression to the southern hemisphere is therefore a naturalextension of what were already doing. By working with Dr Digglesand Digsfish Services we are committed to ensuring a high quality,cost-effective and professional service designed to meet the clientsneeds.

Dr Ben Diggles says the product provides a number of benefitsto fish and shellfish farmers, as well as many in the allied fishhealth industries. Its about time aquaculturalists in the southernhemisphere had access to these innovative tools.

An objective analysis of the costs and benefits associated withvarious disease treatment and prevention strategies is vital intodays economic climate, says Dr Diggles. The partnership withPatterson Peddie Consulting would allow these services to beprovided to those who need them in Australasia and elsewhere inthe southern hemisphere.

See www.pattersonpeddie.com or www.digsfish.com

INFORMATION EXCHANGE ENCOURAGEDThe European Aquaculture Society and the publishers of the newaquaculture trade magazine Aquaculture Health International haveagreed to share articles of relevance to fish and shellfish health inEurope.

Aquaculture Health International is a joint venture betweenPatterson Peddie Consulting in the United Kingdom and VIPPublications Ltd in New Zealand (publishers of NZ Aquaculture).The magazine will initially be published every quarter in bothonline (pdf) and printed formats (ISSN 1176-8630).

The target readership is broad and includes fish healthresearchers, academics, veterinarians, fish health biologists,government scientists, pharmaceutical companies, fish farmers(finfish and shellfish) and aquaculture consultants.

Although the magazines content will evolve in response toreader preferences, it is our intention to provide a lively mix ofglobal fish health news, feature articles, new product releases, in-depth country/species features and a focus on research anddevelopment in immunology, pathology and diagnostics, said themagazines editor, Dr Scott Peddie. Conference reports and bookreviews will also be included.

The European fish and shellfish health scene will be animportant focus for our magazine, Dr Peddie said. As such, weare delighted to have the opportunity to exchange articles andinformation with Aquaculture Europe.

Article concepts from fish health professionals working in Europeshould be directed to Dr Scott Peddie ([email protected])or Alistair Lane ([email protected])

ASIAN FISH VACCINES LAUNCHEDAkzo Nobels Intervet business has launched its first two Asian fish vaccines, Norvax Vibrio Mono and Norvax Strep Si.

Although fish farming is very important in Asia, fish diseasesare a major hurdle to the sustainability and profitability of theindustry, said Alistair Brown, the director of Intervets AquaticAnimal Health division.

Norvax Vibrio Mono, Intervets first fish vaccine to beregistered in Japan, is an immersion vaccine against Vibrioanguillarum infections of Japanese yellowtail. The product isexpected to be followed by several more complex Intervetvaccines, which will be registered in Japan during the next fewyears.

Norvax Strep Si, the companys first Asian fish vaccine outsideJapan, is an immersion and injection vaccine against Streptococcusiniae infections in warm water fish. Full registration of the productis expected in Indonesia and Singapore later this year, whileregistration in several other countries is anticipated over the nextfew years.

NE

WS


Aquaculture Europe 2005: Lessons from the past to optimise the futureNTNU Glshaugen campus, Trondheim, Norway. August 9-12This conference will contain a number of items of interest to fishhealth professionals working in Europe and beyond. Two of thekeynote presentations will be of particular interest. From the United Kingdom, Sunil Kadri and co-authors will

present the paper Fish Welfare: catering for the needs of the fishand the expectations of the consumer.

Luis Tort from Spain will talk on the topic of Fish Health andDisease Prevention: immunological tools and culture management.The parallel poster sessions are also set to reflect an interesting

mix of fish health-related topics, with the organisers placingparticular emphasis on applied research. Over 230 presentationshave been accepted for presentation from 33 countries, includingAustralia and Finland.

A workshop, Recirculating Aquaculture Technology, co-organised by the European Aquaculture Society and theAquaculture Engineering Society will also contain a component onbiosecurity and disease control.Contact the conference secretariat by email [email protected], or by fax at +32 59 32 10 05.To register or for further information, seewww.easonline.org/agenda/en/AquaEuro2005/default.asp

12th European Association of Fish PathologistsConference on Diseases of Fish and ShellfishCopenhagen, Denmark. September 11-16The meeting is expected to include a diverse range of presentationsand poster sessions. A dedicated histopathology workshop,provisionally entitled Histopathology of Early Life Stages, will beheld on September 17.For further information on registration and regular updates onthe conference programme, see www.eafp.org/EAFP2005.html

6th Symposium on Diseases in AsianAquaculture (DAA VI)Colombo, Sri Lanka. October 25-28The Fish Health Section of the Asian Fisheries Society ispresenting the symposium under the theme Aquatic Animal

Health: facing new challenges.A workshop, a training course, an expert

consultation and the 7th Triennial GeneralMeeting of FHS are also being held inconjunction with DAA VI.

The symposium is held every threeyears, with the previous one taking placein Brisbane in 2002. Each has broughttogether more than 200 aquatic animalhealth scientists, students, governmentresearchers and industry personnel fromsome 30 countries to discuss disease-related problems affecting aquacultureproduction and to find solutionsfor them.

The keynote addresses are expected to include: Recent technological advancements in aquatic animal health

and their contribution towards reducing disease risks: areview

Maintaining biosecurity in aquaculture systems: a constraintor a challenge

Pathogen risk assessment: a must for transboundarymovement of aquatics?

Challenges for improving safety of aquatic food: an aquaticanimal health perspective

Aquatic animal health and international trade: quo vadis?Other topics will cover finfish, mollusc and shrimp health,

stakeholder participation and regional cooperation, and the wayforward.For more on the symposium see www.daasix.org or see theFHS website at www.afs-fhs.seafdec.org.ph/ for more detailedinformation about the society and DAA.Expressions of interest to participate or request for inclusionin the mailing list, contact Dr Melba B Reantaso [email protected] using the subject line: DAA VI.

FORTHCOMING CONFERENCES AND MEETINGS

DAA VI

Aquatic animal health:facing new challenges6th SYMPOSIUM ONDISEASES IN ASIAN

AQUACULTURE25-28 October 2005

Aquaculture Health International is the journal for the aquaculture

health professional.

For advertising details, contact the publisher, Keith Ingram.

Phone 0064 9 533 4336Fax 0064 9 533 4337

or email [email protected]


Schering-Plough Aquaculture is the dedicatedaquaculture business unit of the Schering-PloughAnimal Health Corporation, or SPAH. It isfocused on the discovery, development, marketing andtechnical support of aquaculture products worldwide.The company offers a broad line of products andservices for integrated health management to theaquaculture industry.

SPAH says it is one of the worlds leading animalhealth companies, with a global presence in 30countries and distribution in 30 more, ensuring thatall national aquaculture industries will be closelysupported. The companys research and developmenthas generated many new animal health products overthe years, and has led the developments in aquaculturehealth products. It introduced the first licensed fish antibiotic, thefirst immersion and oral vaccines and the first-choice product forcontrolling sea lice.

This expertise, coupled with a specialist aquaculture researchgroup, will continue to bring forward new products for theprevention and control of diseases affecting the aquacultureindustry around the world.

Schering-Plough Animal Health, Aquaculture has continued toexpand the number of registrations of its products for tilapia andshrimp since the launch of AquaVacTM Garvetil and AquavacGarvetil Oral at the WAS meeting in Hawaii in 2004. Theseproducts are now available in Honduras, Ecuador and Mexico,with more registrations in key production markets expected in thenear future.

Aquavac Garvetil is designed to provide broad-spectrumprotection against streptococcosis caused by Streptococcus iniaeand Lactococcus garvieae in farmed tilapia.

The vaccination programme follows SP Aquacultures strategy ofproviding total protection vaccination programmes which enablefarmers to use the most practical and cost-effective method ofvaccination available to prevent disease outbreaks throughout theproduction cycle.

The programme is designed to provide protection from the earlystages of the farming cycle (1 gram) until harvest. This long-termprotection is achieved by the strategic use of AquaVac GarvetilOral as a booster vaccine. Oral booster vaccination is nowbecoming a common feature of aquaculture health management asSPAH introduces the technology to a growing number of countriesand fish species. Most recently AquaVacTM Vibrio Oral vaccine forpreventing vibriosis in sea bass and rainbow trout was approved inFrance.

The AquaflorTM broad-spectrum antibiotic, discovered anddeveloped by Schering-Plough and recognised for its safety andefficacy in salmonid species, is also a highly effective tool forcontrolling mortality due to Streptococcus spp. in farmed tilapia.

In addition to its products for health management in tilapia,SPAH Aquaculture provides a range of tools for preventing andcontrolling disease in shrimp farms. The leading product in thisrange is AquaVac Vibromax.

This product is designed to increase the growth, survival andquality of shrimp exposed to vibriosis challenges. Since its originallaunch in Mexico last year, considerable numbers of shrimp havebeen treated with excellent results. Enhanced survival, size, growthrates (SGR) and food conversion rates (FCR) in treated shrimp

were enhanced throughout the production cycle following theadministration of AquaVac Vibromax to shrimp PLs.

See www.spaquaculture.com

SP Aquaculture wishes the team at Aquaculture Health Internationalbest wishes with the launch of this important new magazine. As acompany providing health management solutions around the world tomany different species, the concept of pulling practical applied fish healthunder a single forum to update and inform is extremely appealing.

COMPANY FOCUS:SCHERING-PLOUGH AQUACULTURE

Oral boostervaccination is nowbecoming acommon feature ofaquaculture healthmanagement asSPAH introduces thetechnology


THE SCOURGE OF BONAMIAOyster farmers throughout the world fear microcell parasites ofthe genus bonamia as a silent scourge which can slowly and quietlydrive them out of business. These parasites belong to a smallphylum of protozoans called the Haplosporidia.

Other well known haplosporidians include Haplosporidium (Hnelsoni, which causes MSX disease in Crassostrea virginica on theeastern coast of the United States), and Marteilia (M refringens causesAber disease in Ostrea edulis in France, while M sydneyi causes QXdisease in Sydney rock oysters (Saccostrea glomerata), in Australia.

All are OIE-listed notifiable pathogens of oysters worldwide, buteven within this group, bonamia is emerging as arguably the mostprominent and widespread haplosporidian disease agent of oysterfarming in the 21st century.

Bonamia microcells are very small (2-3 microns in diameter)and infect mainly oyster blood cells (Figure 1). The blood celldetects the parasite as foreign and engulfs it in a futile attempt tokill the parasite. However, bonamia survives and reproduces insidethe blood cells, feeding off the cells lipid reserves).

They divide until the cell bursts and dies, liberating up to 10 ormore parasites, after which the process is repeated. Ironically,environmental conditions correlating to productive oyster culture(high water temperatures, high host densities and the oysters inspawning condition) also tend to favour bonamia, at least in NewZealand.

When conditions are right, the parasite multiplies there in amind-boggling fashion. Our laboratory calculated that a heavilyinfected New Zealand dredge oyster contains 300 million to 500million microcells when it dies, which is pretty horrific for theoysters around it when you consider that transmission is directthrough the water, and the infective dose required to kill half ofexposed oysters is only around 80,000 microcells.

The first described species of bonamia, namely B ostreae, caused

epizootic disease in populations of Ostrea edulis in France in 1979.Further research indicated that the parasite was probably introducedinto France and Spain through the importation of O edulis seedfrom the United States, where undescribed microcell diseases hadaffected native flat oyster populations as early as the 1960s.

B ostreae subsequently spread throughout Europe, killing off anychances of viable flat oyster culture in many countries, a sombrelesson on the disease risks of oyster translocation. Then, between1986 and 1992, massive mortalities of over 90 percent of dredgeoysters (Ostrea chilensis) were recorded in a wild fishery inFoveaux Strait in New Zealand. The deaths were found to be dueto a new parasite, Bonamia exitiosa.

There is evidence that this particular parasite was present indredge oysters as far back as at least the 1960s, and that it wasprobably always endemic in New Zealand. The increasingfrequency and severity of epizootics in this fishery in recent years(another epizootic occurred between 1999 and 2004) are thoughtto be related to environmental stressors such as modification ofbenthic substrate by dredges, which may have increased thesusceptibility of oysters to bonamiosis.

More recently there is evidence that another, much rarer species ofbonamia also exists in New Zealand oysters, but almost nothing isknown about this species other than it divides synchronously insidethe oyster blood cell (Figure 2).

BONAMIA IN AUSTRALIAAustralia now recognises that there are also two species of bonamia.The first discovery of bonamia was associated with mortalities offlat oysters Ostrea angasi in southeastern Australia in early 1991.

This parasite was morphologically indistinguishable from Bexitiosa. This could be because large numbers of live New Zealanddredge oysters were moved from New Zealand to Australia in theearly 1900s to replenish stocks of O angasi, which suffered frommassive mortalities in the late 1800s. However, populations of O

FOCUS ON SHELLFISH:Bonamia - uncovering microcell secretBY DR BEN DIGGLES (DIGSFISH SERVICES PTY LTD, AUSTRALIA)

FIGURE 1. HISTOLOGY OF A HEAVY BONAMIA EXITIOSUS INFECTIONSHOWING NUMEROUS MICROCELLS (ARROWED) IN THE HAEMOCYTES OF ADREDGE OYSTER OSTREA CHILENSIS FROM NEW ZEALAND. SCALE BAR = 10 M

FIGURE 2. STAINED HEART IMPRINT SHOWING SYNCHRONOUS DIVISION INWHAT IS THOUGHT TO BE A SECOND SPECIES OF BONAMIA IN THE DREDGE

OYSTER OSTREA CHILENSIS FROM NEW ZEALAND. SCALE BAR = 10 M


angasi around Tasmania and in Western Australia also haveBonamia sp. In the absence of known movements of New Zealandoysters into these areas, it is possible that Bonamia sp has beenpresent in Australia all along, as it was in New Zealand.

That scenario would certainly explain the massive mortalities ofO angasi reported in the late 1800s before the introduction of theNew Zealand oysters.

Australias second species of bonamia was originally described asMikrocytos roughleyi, and had been associated with the diseasesyndrome called winter mortality in the Sydney rock oyster(Saccostrea glomerata) as far back as the 1920s.

However, there are fundamental differences between this parasiteand the ultrastructure of the only other member of the genus,Mickrocytos mackini (the cause of Denman Island disease inC gigas in Canada).

Subsequent studies using modern DNA technology have nowindicated that M roughleyi was in fact another species of bonamia,namely B roughleyi. This parasite is therefore particularlyinteresting, as unlike other bonamia species, it appears to causedisease in winter, not summer.

BONAMIA IS BOOMINGIn the past, the geographical distribution of microcell infectionstended to follow the movements of a small number of expertpathologists, such is the difficulty in detecting these parasites withtraditional diagnostic techniques. People like Ralph Elston andMike Hine certainly have contributed enormously towards thepresent knowledge of the parasite bonamia and the diseasebonamiosis. However, since the mid-1990s, the emergence of betterdiagnostic tests, better informed and equipped aquatic animal healthspecialists and the listing of the disease with the OIE has meant newdiscoveries are now spread more evenly around the world.

Recently, isolates of bonamia-like parasites have been reportedfrom O chilensis in Chile, C gigas in Australia, Crassostrea ariakensisin North Carolina and Ostrea puelchana in Argentina.

In fact, Dr Hine confirms that there are now 11 known bonamiaor bonamia-like pathogens currently being studied around theworld. To fully understand the significance of the more recentlydiscovered isolates, clearly their taxonomic relationships within thegenus need to be established.

Modern DNA-based molecular diagnostic techniques are beingused forensically to painstakingly piece together a global picturethat gets more interesting with each new finding. For example,preliminary findings using rDNA sequencing techniques havefound that the Australian Bonamia sp is closer to the Chileanbonamia than it is to B exitiosa in New Zealand.

Even more interesting is the fact that the isolate found inCrassostrea ariakensis in North Carolina appears to have exactly thesame sequence as the Australian Bonamia sp. In the absence ofknown movements of oysters between the two areas this appearsimpossible at first, until it is realised that bonamia can probably betransmitted via oyster spat fouling boat hulls. Therefore theBonamia sp in C ariakensis may indeed have been introduced fromAustralia by shipping.

THE FUTUREClearly scientists are only beginning to uncover the secrets held bythis intriguing group of parasites. Modern, sensitive PCR-baseddiagnostic techniques (Figure 3) can now detect latent sub-clinicalinfections which were previously impossible to detect usingtraditional light microscopic techniques.

Wider use of these new tools may well shed light onimportant epizootiological information that is currentlylacking. They will almost certainly indicate that the distributionof these parasites is as much influenced by biogeography astranslocation, and that they may indeed threaten economicaquaculture of many more species of oysters worldwide.Fortunately there is light at the end of the tunnel with thedevelopment of bonamia-resistant strains of oysters appearingto be a workable solution to the problem of microcells causingmacro-problems in oyster culture.

FURTHER READINGBurreson EM, Stokes NA, Carnegie RB, Bishop MJ (2004). Bonamiasp (Haplosporidia) Found in Nonnative Oysters Crassostreaariakensis in Bogue Sound, North Carolina. Journal of AquaticAnimal Health 16. pp 1-9Cranfield HJ, Dunn A, Doonan IJ, Michael KP (2005). Bonamiaexitiosa epizootic in Ostrea chilensis from Foveaux Strait, southernNew Zealand between 1986 and 1992. ICES Journal of MarineScience 62. pp 3-13 Hine PM (1996). The ecology of Bonamia and decline of bivalvemolluscs. New Zealand Journal of Ecology 20. pp 109-116

FIGURE 3. THE EMERGENCE OF MOLECULAR DIAGNOSTIC METHODS HASREVOLUTIONISED THE DETECTION OF BONAMIA INFECTIONS IN OYSTERS. BUT

AT THIS STAGE OF THEIR DEVELOPMENT THEY HAVE PROBABLY GENERATEDMORE QUESTIONS THAN ANSWERS. DRS DIGGLES (LEFT) AND COCHENNEC-

LAUREAU AT WORK IN THE MOLECULAR LABORATORY

In the absence of knownmovements of New Zealand

oysters into these areas, it ispossible that Bonamia sp has

been present in Australia allalong, as it was in New Zealand

VIP.

AC04

WHAT IS SRS?Salmonid rickettsial syndrome (also known as salmon rickettsialsyndrome piscirickettsiosis, coho salmon septicaemia and huitodisease) is considered to be the most important disease problem inthe Chilean salmon farming industry. In some years it causeseconomic losses of over US$100 million. SRS was first reportedfrom Chile in 1989, but (Pisci)rickettsia-like organisms (RLO) arenow frequently associated with disease syndromes in salmonid andnon-salmonid fish from both fresh and salt water worldwide.

In 1989 this disease was considered to be the cause of death of anestimated 1.5 million coho salmon, many near market size. A yearlater, the disease was also found in Atlantic salmon and up to 90percent mortality was seen on some farms. However, outbreaks ofSRS in other countries have not reached the levels of the Chileanoutbreaks. For example, variable and inconsistent mortality of 0.6- 15 percent has been reported in Canada and Norway.

WHAT CAUSES THE DISEASE?SRS is caused by the Gram-negative bacterium, Piscirickettsiasalmonis. This was the first rickettsia-like bacterium to berecognized as a pathogen of fish. P salmonis is the first of the RLOof fish to be fully characterised. Since its recognition, the impact ofRLO in fish has become increasingly apparent.

Growing awareness of the emergence of these intracellularorganisms has led to the discovery of rickettsial diseases amongdiverse species of fish from different geographic locations andaquatic environments. The source, reservoir and mode oftransmission of many of these agents, as well as consistentlyeffective methods of disease prevention and control, remain to beestablished.

HOST RANGE AND GEOGRAPHIC DISTRIBUTIONSRS disease in Chile typically occurs in marine waters during theon-growing process from smolt to harvest. It has also been isolatedfrom freshwater cages of coho salmon and trout.

The disease was originally predominant in coho salmon(Oncorhynchus kisutch), but is now recognised to cause seriouslosses in all farmed salmonid fish species, including Atlanticsalmon (Salmo salar), rainbow (steelhead) trout (O mykiss),chinook salmon (O tshawytscha), pink salmon (O gorbuscha) andmasu salmon (O masou).

Piscirickettsia sp are commonly found in fish worldwide,including Chile, Canada, Ireland, Scotland and Norway, but are ofmajor economic importance only in Chile to date. Thedistribution of P salmonis and RLO is therefore widespread.

Several reports describing RLO infections in non-salmonidfinfish also exist. For example, about 10 years ago, an RLO wasidentified as the causative agent of an outbreak associated withmass mortality among pond-reared tilapia in Taiwan. Also, RLO-related mortalities in juvenile European sea bass at 12 to 15 degreesCelsius in sea cages have been reported along the FrenchMediterranean coast.

TRANSMISSION AND EPIDEMIOLOGYAt present there are few reports of P salmonis coming from wildsalmonids, although it is likely that the bacterium is present innaturally occurring populations of marine fish. Horizontaltransmission (ie between fish) has been reported in marine-farmed salmon two weeks after the introduction of pathogen-freefish into infected sites.

The extended extracellular survival time of this organism in saltwater (several weeks at 5 to 20 Celsius) may be of sufficient

SRS PATHOLOGY IN SALMON. NOTE THE SEVERE INFLAMMATION ANDMULTIFOCAL NECROSIS IN LIVER AND SPLEEN. HAEMORRHAGIC ASCITES

ARE ALSO OBSERVED

(Adapted from an article that appeared in Intervets Aquatic Animal Health Newsletter no. 9, November 2004.See www.intervet.com/aah/newsletters.asp)

FOCUS ON FINFISH:An overview of SalmonidRickettsial Septicaemia, or SRSBY DR OSCAR PARRA AND DR SERGIO VASQUEZ (INTERVET LTDA, CHILE) AND DR WILLIAM J ENRIGHT (INTERVET INTERNATIONAL BV, THE NETHERLANDS)

A BEAUTIFUL, CALM DAY AT A FISH FARMON LAKE TEPUHUEICO, CHILE



duration to permit horizontal transmission without a vector.Experimentally, it is documented that the bacterium can enterthrough the intact skin and gills, although the mode of entry is stillnot clear.

The possibility of vertical transmission (ie from parent tooffspring) of P salmonis now looks more and more likely,according to recent research in Chile. Apparently there is anadhesion complex that allows the pathogen to enter the salmonegg. There is even a suggestion that this complex may be involvedin fish-to-fish transmission.

Currently, no alternative host has been identified and the source,reservoir and means of transmission of P salmonis remainimportant areas of research.

The course of the clinical disease is typically chronic to subacutein nature, with mortalities normally developing 10 to 12 weeksafter the transfer of fish to seawater and lasting approximately 10weeks before they diminish. Virtually all stocks become infected,and they usually experience more then one clinical episode,typically in the spring and autumn.

CLINICAL SIGNS, GROSS PATHOLOGY AND HISTOPATHOLOGYSRS can have a substantial economic impact at affected farm level,particularly in Chile, as typical cumulative mortality averages 20percent during the 18-month saltwater production time to harvest.Affected fish are lethargic, dark in colour, anorexic, anaemic withmottled focal lesions within the liver, show respiratory problemsand swim near the surface.

The first signs observed are often haemorrhages and lesions ofthe skin. The lesions range from small areas to shallow ulcers up to2cm in diameter. Internally, the kidney is swollen and the spleenenlarged. Petechial haemorrhages are found on the swim bladderand viscera. Diagnostic ring-shaped, cream-coloured lesions arepresent on the livers of chronically infected fish. However, in acutecases, death may be the only gross sign of disease.

Histological changes have been classified into the broad categoryof necrosis and inflammation. Inflammatory cells, fibrosis, ageneralised coagulative necrosis, tubular degeneration and necrosisof the endothelium infiltrate the liver, spleen, intestine andhaematopoietic cells of the kidney. Moribund fish are anaemic,and haematocrit is often 20 percent to 50 percent of normal.

The rickettsial organism infects a variety of cells, includingcirculating macrophages, in which they can replicate and cause celllyses. It also enters brain tissue, thus affecting swimming ability.The mechanisms by which P salmonis can enter target cells, avoidintracellular killing and survive inside the host are unclear.

DIAGNOSISAn initial diagnosis of piscirickettsiosis can be made from grosslesions and is supported by examining tissue sections.Confirmation of the diagnosis requires isolation and/or serologicalidentification of the causative organism. An indirect fluorescentantibody technique (IFAT) and immuno-histochemistry have beendeveloped as alternative procedures to detect P salmonis.

These latter techniques are faster and more specific thanhistochemical staining. However, they require additionalspecialised equipment and are more expensive. The detection of Psalmonis in cultivated salmonids via a nested PCR using universalprimer is coming on stream and will be important for diagnosingthis disease.

DISEASE CONTROLChemotherapy. In laboratory studies, P salmonis has been shownto be sensitive to various antibiotics, including streptomycin,gentamicin, erythromycin, chloramphenicol and oxytetracycline,but shows resistance to penicillin, penicillin G and spectinomycin.

However, the use of medicated feed to control intracellularpathogens, including P salmonis, has been largely unsuccessful,possibly because antibiotic levels may not reach sufficientconcentrations within the host cells. Nevertheless, injection ofbroodstock with antibiotics before leaving seawater in order tocontrol the typical summer SRS outbreak is common.

Vaccine development. Although commercial vaccines against Psalmonis have been made available recently, there is little publishedinformation or field experience on their efficacy or economicvalue. However, several institutes and pharmaceutical companies,including Intervet, have active research programmes directedtowards developing efficacious vaccines.

MANAGEMENTOutbreaks frequently occur after smolt transfer to seawater, butgood management practices do help. Such approaches include theearly removal of dead and clinically diseased fish, with appropriatesanitary disposal of blood from harvested fish, reducing fishstocking density and providing periods of site fallowing. Otherstrategic measures include routine screening broodstock, rejectingeggs from positive fish and individual incubation of egg batches.

Further information regarding horizontal and verticaltransmission, pathogenesis, intracellular survival andimmunogenicity is needed to support future control strategies. Inaddition, information on the geographic location and speciesdistribution of P salmonis among isolates and stocks of fish will behelpful in developing management and control strategies in thefuture.

FURTHER READINGBruno DW and Woo PTK (2002). Sporadic, emerging diseases anddisorders. Diseases and disorders of finfish in cage culture. Eds:Woo PTK, Bruno DW, Lim LHS. CAB International. pp 305-343Fryer JL, Mauel MJ (1997). The Rickettsia: an emerging group ofpathogens in fish. Emerging Infectious Diseases 3. pp 137-144Kent ML and Poppe TT (2002). Infectious diseases of coldwater fishin marine and brackish water. Diseases and disorders of finfish incage culture. Eds: Woo PTK, Bruno DW, Lim LHS. CABInternational. pp. 61-105

A PROFESSIONAL VACCINATION TEAM AT WORK IN CHILE. SRS VACCINES ARENOW COMMERCIALLY AVAILABLE

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