international response to infectious salmon anemia: prevention

United StatesDepartment ofAgriculture

Animal andPlant HealthInspectionService

United StatesDepartment ofthe Interior

U.S. GeologicalSurvey

United StatesDepartment ofCommerce

National MarineFisheries Service

TechnicalBulletin No. 1902

International Responseto Infectious SalmonAnemia: Prevention,Control, and Eradication

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Photo credits: The background illustration on the front cover wassupplied as a photo micrograph by Michael Opitz, of the Universityof Maine, and is reproduced by permission. The line art of salmoncame from the 1973 book The Salmon: Their Fight for Survival, byAnthony Netboy. Houghton Mifflin Company is the copyright holderon the line art, which is reproduced by permission. Images insidethe proceedings were supplied by the senior authors. For reproduc-tion rights, please consult each senior author using contactinformation in appendix 1, Authors Affiliations.

Issued April 2003

United StatesDepartment ofAgriculture

Animal andPlant HealthInspectionService

United StatesDepartment ofthe Interior

U.S. GeologicalSurvey

United StatesDepartment ofCommerce

National MarineFisheries Service

TechnicalBulletin No. 1902

International Responseto Infectious SalmonAnemia: Prevention,Control, and Eradication

Proceedings of a SymposiumNew Orleans, LASeptember 34, 2002

Otis Miller, D.V.M., M.S., andRocco C. Cipriano, Ph.D.,Technical Coordinators1

1Dr. Miller is a senior staff veterinarian and national aquaculture coordinator with the USDAAnimaland Plant Health Inspection Services Veterinary Services in Riverdale, MD. Dr. Cipriano is seniorresearch microbiologist with the USDIU.S. Geological Survey National Fish Health ResearchLaboratory in Kearneysville, WV.

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Suggested citation for the book, using the bibliographic style of the American NationalStandards Institute:

Miller, Otis; Cipriano, Rocco C., tech. coords. 2003. International response to infectioussalmon anemia: prevention, control, and eradication: proceedings of a symposium; 34September 2002; New Orleans, LA. Tech. Bull. 1902. Washington, DC: U.S. Department ofAgriculture, Animal and Plant Health Inspection Service; U.S. Department of the Interior, U.S.Geological Survey; U.S. Department of Commerce, National Marine Fisheries Service. 194 p.

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The suppression of infectious salmon anemia (ISA) is key to protectingaquaculture, the fastest growing segment of the U.S. agricultural economy.Government stewards of the salmon resource of the North Atlantic mustcommunicate and cooperate to eradicate ISA before it becomes endemic.Sharing the science already learned by researchers in Scandinavia andthe United Kingdom is essential to developing an effective managementstrategy.

Secretary of Agriculture Ann Veneman acknowledged the importanceof ISA when she authorized the expenditure of $8 million in fiscal years2002 and 2003 to control and eradicate the disease. APHIS receivedpass-through funding for ISA research and control efforts in December2001 and, in spring 2002, put into place program standards to eradicatethe disease.

In September 2002, the U.S. Department of Agricultures Animal andPlant Health Inspection Service (APHIS) hosted a symposium on ISA withassistance from the U.S. Department of the Interiors U.S. GeologicalSurvey and the U.S. Department of Commerces National Marine Fish-eries Service. The American Veterinary Medical Association suppliedorganizational expertise as well. This 2-day event was held in connectionwith the International Symposium on Aquatic Animal Health in NewOrleans. These symposium proceedings capture not only the formalscientific presentations but also a court reporters transcript of theinformal presentations at the end of the second day, which addressedreal-world considerations for ISA prevention, control, and eradication.

Given the importance of the information shared at the meeting,APHIS staff members have pulled out all the stops to produce this book in8 months. Once our supply of free copies is exhausted, copies can bepurchased from the U.S. Department of Commerces National TechnicalInformation Service, 5285 Port Royal Road, Springfield, VA 22161. Also,a .pdf version will be placed on the Web site of APHIS VeterinaryServices at .

I hope you find the information presented at the conference as usefulas I did.

W. Ron DeHavenDeputy Administrator, Veterinary ServicesAnimal and Plant Health Inspection ServiceU.S. Department of AgricultureWashington, DC

Letter of Transmittal

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http://www.aphis.usda.gov/vs/aquaculture

On behalf of Secretary of Agriculture Ann Veneman, APHIS AdministratorBobby Acord, and the Deputy Administrator for Veterinary Services, RonDeHaven, thanks for your interest in learning more about infectioussalmon anemia (ISA). This book documents the scientific paperspresented at a 2-day symposium held September 34, 2002, in NewOrleans, LA, during the weeklong meeting of the International Symposiumon Aquatic Animal Health. In addition to 18 formal scientific presenta-tions, we have captured comments from individuals who spoke brieflyduring an open forum held at the end of day 2 of the symposium. Whilethe formal presentations were submitted in advance and put throughrigorous peer review, the forum talks were not vetted or corrected, otherthan for clarity. We took the precaution of using a local court reporter tocapture the forum talks verbatim since those speakers were not requiredto submit manuscripts.

The meeting itself was structured to provide an internationalresponse to ISA using the themes of prevention, control, and eradication.Four moderators introduced the main subject topics and the speakerspresentations in the areas of international applied research response,diagnostic and laboratory response, management response, and regula-tory response. Our speakers provided the most current internationalknowledge on the extent of ISA infection in various countries, includingthe number of salmon farms affected, depopulation statistics, and relatedissues such as indemnification, regulation, and management. Alsocovered were effective and ineffective management procedures, projectedoutcomes of procedures in current use, and new developments in appliedISA science and research, including diagnostics and prevention.

Presenters represented five countries: Canada, Chile, Norway,Scotland, and the United States. When the number of speakers reached19, we split the meeting into 2 sessions on successive days. The secondday culminated in a panel discussion entitled Practical Future Consider-ations for ISA Prevention, Control, and Eradication. This open forum wasdesigned to allow audience participation and permit ISA experts not onthe official agenda to address topics of interest.

It always takes a team of workers to organize and execute a meetinglike ours and to bring its results to printed form afterward. We will giveyou more particulars on this process and identify all the major players inthe Acknowledgments section immediately following this Foreword.

Should you wish to contact any speakers or forum participants formore details, appendixes 1 and 2 provide complete contact information.

Foreword

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We look forward to working with you in helping the aquacultureindustries and natural-resource agencies manage ISA. The symposiumheld in New Orleans was an important national and international step incoming to grips with this significant aquatic animal health threat.

Otis Miller, Jr., D.V.M., M.S.National Aquaculture CoordinatorChair, ISA Symposium Planning CommitteeUSDAAPHISVeterinary ServicesRiverdale, MD

Rocco C. CiprianoSenior Research MicrobiologistU.S. Department of the InteriorU.S. Geological SurveyNational Fish Health Research LaboratoryKearneysville, WV

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The Veterinary Services unit of USDAs APHIS, the U.S. GeologicalSurvey, the National Marine Fisheries Service, and Interiors U.S. Fish andWildlife Service at the Federal levelalong with Maines Department ofMarine Resources at the State levelare hard at work to ensure asuccessful prevention, control, and eradication program to manageinfectious salmon anemia (ISA) in the United States. Similar efforts arebeing mounted in Canada, Scotland, and Norway, all of which sufferedISA outbreaks before the disease came to U.S. waters.

APHIS supports an integrated approach that uses the expertise of allrelevant Federal agencies, States, and Canadian Provinces, as well asindustry stakeholders in an international partnership for development andimplementation of programs involving aquaculture. Because ISArepresents a disease threat to the salmon industry on both sides of theAtlantic, integrating the scientific and regulatory response to this diseaseacross national borders is extremely important. The creation of the firstinternational symposium on ISA held in the United States is an initial stepin acknowledging that this disease is everybodys issue. We [Otis Millerand Rocco Cipriano] organized the symposium but not in a vacuum. Wegratefully acknowledge the expertise and cooperation of the OfficeInternational des Epizooties (Paris), the American Veterinary MedicalAssociation (headquartered in Schaumburg, IL), the Canada Departmentof Fisheries and Oceans, the Norwegian Animal Health Authority,Scotlands famous marine research lab in Aberdeen, aquaculture units inthe Provincial Governments of New Brunswick and Prince Edward Island,and the Maine Aquaculture Association in supplying experts for thepodium.

Rocco Cipriano provided yeoman service in the summer of 2002 insetting up a peer-review process for all the manuscripts formallypresented. Keeping track of the peer reviewers comments and makingsure that speakers took those comments into account in revising theircontributions before the meeting in September was a gargantuan task.Some readers may not understand that Roccos role as a TechnicalCoordinator for the book far exceeds that of an editor. He also served asthe official reviewer of the entire text for the U.S. Geological Survey. Wecould not have made this proceedings without his help before, during, andafter the meeting itself.

The following individuals also worked on putting together theprogram: Peter Merrill, D.V.M., MicroTechnologies, Inc., Richmond, ME Jill Rolland, fisheries biologist with USDAAPHISVeterinary Services,Riverdale, MD Alasdair McVicar, Ph.D., DFO, Aquaculture and Fish Health, Ottawa, ON

Acknowledgments

vi

David Scarfe, D.V.M., Ph.D., assistant director of scientific activities withthe American Veterinary Medical Association, Schaumburg, IL Kevin Amos, Ph.D., national fish health coordinator for the U.S.Department of Commerces National Marine Fisheries Service, Olympia,WA Jim Winton, Ph.D., chief of the fish health section at the U.S. GeologicalSurveys Western Fisheries Research Center, Seattle, WA Gilles Olivier, Ph.D., Canada Department of Fisheries and Oceans,Ottawa, ON

The following individuals helped by volunteering to act as moderatorsfor the four subsections of the program: David Scarfe, D.V.M., Ph.D. Laura Brown, Ph.D., group leader of genome sciences, NationalResearch Council of Canada, Halifax, NS Paul J. Midtlyng, D.V.M., Ph.D., VESO, Oslo, NO Carey Cunningham, Ph.D., Fisheries Research Services MarineLaboratory, Aberdeen, UK Patricia Barbash, fishery biologist, USDI U.S. Fish and Wildlife Service,Northeast Fisheries Research Center, Lamar, PA

Patricia Barbash and Kevin Amos also provided interagency review of theentire text outside USDA.

Behind the scenes, the following individuals worked on preparing thebook for publication: Janet S. Wintermute, writer/editor, USDAAPHISLegislative and PublicAffairs, Riverdale, MD Heather Curlett, designer, USDA Design Division, Beltsville, MD Jill Rolland and Bronte Williams, manuscript traffic and preparation,USDAAPHISVeterinary Services, Riverdale, MD Anita McGrady, printing specialist, USDAAPHISLegislative and PublicAffairs, Washington, DC

Their single-minded dedication to this project is the reason APHISwas able to issue the proceedings in 8 months.

In closing, the fourth International Symposium on Aquatic AnimalHealth was a highly approriate setting for a symposium on ISA. If it werenot for the unselfish efforts of the organizer of the symposium on aquaticanimal health, Dr. Ron Thune, as well as the program chairs, Drs. JohnHawke and Jerome La Peyre, APHIS could not have held this meeting.

vii

And since money drives all endeavors, and bookmaking is no exception,now is the time to acknowledge financial contributions from APHIS, theNational Marine Fisheries Service, and the U.S. Geological Survey.

I hope you will find that this book enhances your understanding ofISA and supports you in your commitment to help the scientific communitydeal with it.

Otis Miller, Jr., D.V.M., M.S.National Aquaculture CoordinatorUSDAAPHISVeterinary Services4700 River Road, Unit 46Riverdale, MD 20737(301) [email protected]

viii

1 Infectious Salmon Anemia: The Current Stateof Our Knowledge

Rocco C. Cipriano and Otis Miller, Jr.

13 Role and Function of the OIE Fish DiseasesCommission in the Field of Aquatic AnimalHealth

Tore Hstein

International Applied Research Response

25 A Comparative Review of Diagnostic AssaysUsed To Detect Infectious Salmon AnemiaVirus in the United States

Peter L. Merrill

39 The Development of Infectious Salmon AnemiaVirus Vaccines in Canada

Frederick S.B. Kibenge, Molly J.T. Kibenge,Tomy Joseph, and John McDougall

51 Epidemiologic Study of Infectious SalmonAnemia in Maine: Combining the SubjectiveWith the Objective in Risk Factor Estimation

Lori Gustafson, Steve Ellis, and Larry Hammell

55 The Epidemiology of Infectious Salmon Anemiain Scotland

Alexander G. Murray

International Diagnostic and LaboratoryResponse

63 Improved Diagnosis of Infectious SalmonAnemia Virus by Use of a New Cell Line DerivedFrom Atlantic Salmon Kidney Tissue

Jill B. Rolland, Deborah A. Bouchard, and James R. Winton

Contents

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69 Evaluation of Infectious Salmon AnemiaDiagnostic Tests

Carol A. McClure, K. Larry Hammell, Ian R. Dohoo, Henrik Stryhn,and Leighanne J. Hawkins

75 Development of a Strain Typing Assay forInfectious Salmon Anemia Virus (ISAv)

Marcia Cook, Sherry Vincent, Rachael Ritchie, and Steve Griffiths

87 The Genetics of Infectious Salmon AnemiaVirus

Carey O. Cunningham and Michael Snow

International Management Response

97 Infectious Salmon Anemia in Norway and theFaroe Islands: An Industrial Approach

Cato Lyngy

111 The Eradication of an Outbreak of ClinicalInfectious Salmon Anemia From Scotland

Ronald M. Stagg

125 Practical Grower Experience in the ProactivePrevention and Control of Infectious SalmonAnemia

Sebastian M. Belle

135 Survey of Nonsalmonid Marine Fishes forDetection of Infectious Salmon Anemia Virusand Other Salmonid Pathogens

Sharon A. MacLean, Deborah A. Bouchard, and Stephen K. Ellis

145 Infectious Salmon Anemia in New Brunswick:An Historical Perspective and Update onControl and Management Practices(19972002)

Sandi M. McGeachy and Mark J. Moore

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International Regulatory Response

155 Experiences With Regulatory Responses toInfectious Salmon Anemia in Norway

Kristin E. Thorud and Tore Hstein

161 Regulatory Aspects of Infectious SalmonAnemia Management in Scotland

Alasdair H. McVicar

167 Design and Implementation of an InfectiousSalmon Anemia Program

Otis Miller, Jr.

175 Presentations From the Open Forum

191 Appendix 1Authors Affiliations

193 Appendix 2Affiliations of the Speakers at theOpen Forum

xi

1

Abstract: Infectious salmon anemia (ISA) is a highlyinfectious viral disease that causes acute mortality princi-pally among Atlantic salmon (Salmo salar). The cause ofISA is an orthomyxolike enveloped virus that replicatesthroughout most host tissues, including midkidney, headkidney, liver, spleen, intestine, gills, muscle, and heart. Thevirus is cultured in Atlantic salmon head kidney (SHK1)cells, in the Chinook salmon (Oncorhynchus tshawytscha)embryo (CHSE214) cell line, and within the TO cell linedeveloped from head kidney leucocytes. Clinical signs ofthe disease may include pale gills, ascites, liver congestion,enlarged spleen, petechial hemorrhages within visceral fat,congestion of the gut, and severe anemia. The disease ispronounced in the marine environment, where it is mostoften transmitted by cohabitation with infected live salmon,infected biological materials, or contaminated equipment.Control of ship and personnel movements among infectedsites, destruction of infected lots, and the closure andfallowing of virus-contaminated areas may be used toreduce the likelihood of further spread of the disease.

Hosts and Geographic Range

Infectious salmon anemia (ISA) is a highly infectiousdisease of Atlantic salmon (Salmo salar) that wasfirst reported in Norwegian aquaculture facilities. Thedisease has since been described among premarketAtlantic salmon in Scotland (Bricknell et al. 1998),New Brunswick, Canada (Lovely et al. 1999, Jones etal. 1999a), the United Kingdom (Rodger et al. 1999),the Cobscook Bay region of Maine (Bouchard et al.2001), and in the Faroe Islands (Anonymous 2000).The virus that causes ISA has also been detectedamong coho salmon (Oncorhynchus kisutch) in Chile(Kibenge et al. 2001). In Canada, the disease wasfirst characterized as a new condition termedhemorrhagic kidney syndrome or HKS (Byrne et al.1998). The pathology of HKS was later shown to becaused by ISAv (Bouchard et al. 1999, Lovely et al.1999), although laboratory confirmation of ISA virus(ISAv) was initially complicated by dual isolation ofthat virus and a nonpathogenic Toga-like virus fromHKS samples (Kibenge et al. 2000a).

The rapid invasion of ISAv into three bays withinNew Brunswick and its subsequent spread among 21

Infectious Salmon Anemia: The Current Stateof Our Knowledge

Rocco C. Cipriano and Otis Miller, Jr.1

1 Dr. Cipriano is with the U.S. Geological Surveys NationalFish Health Research Laboratory in Kearneysville, WV. Dr.Miller is with USDAAPHIS Veterinary Services inRiverdale, MD.

farms (Bouchard et al. 1998) indicate the severenature of the threat that ISA represents for Atlanticsalmon aquaculture. Furthermore, the annual cost ofISA outbreaks among farmed fish in 1999 wasreported, in U.S. dollars, to be $11 million in Norwayand $14 million in Canada. The 199899 epidemicsin Scotland were valued at a cost of $32 million(Hastings et al. 1999). Although epizootics of ISAhave been specifically associated with culturedsalmon (Department of Fisheries and Oceans[DFO]Canada), biologists have also detected thepresence of ISAv among Atlantic salmon populationsthat are wild or have escaped from aquacultureoperations at the Magaguadavic River fish trap (Bayof Fundy, NB). In addition to Atlantic and Chinooksalmon, the pathogen infects, but has not produceddisease in, freshwater brown trout (Salmo trutta)(Nylund et al. 1995a), sea trout (S. trutta) (Nylundand Jakobsen 1995), and rainbow trout(Oncorhynchus mykiss) (Nylund et al. 1997).Although the virus has been detected in saithe(Pollachius virens), it is unable to replicate in suchhosts (Raynard et al. 2001).

Etiology

The cause of ISA is an enveloped virus 45140 nm indiameter (Dannevig et al. 1995b) with a buoyantdensity 1.18 g/mL in sucrose and cesium chloridegradients. It shows maximum replication at 15 oC butstrongly reduced replication at 25 oC (Falk et al.1997). The virus may be cultured in the SHK1 cellderived from Atlantic salmon pronephros cells andproduces variable cytopathic effects (CPE) between3 and 12 days after inoculation (Dannevig et al.1995a,b; Kibenge et al. 2000b). The ISAv alsoreplicates and produces CPE within the Atlanticsalmon head kidney (ASK) cell line developed byDevold et al. (2000) and the TO cell line developedfrom Atlantic salmon head kidney leukocytes byWergeland and Jakobsen (2001). Some, but not all,strains of ISAv will also replicate in Chinook salmon(Oncorhynchus tshawytscha) embryo (CHSE214)cells and produce CPE between 4 and 17 days afterinoculation (Kibenge et al. 2000b). The virus also

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International Response to Infectious Salmon Anemia:Prevention, Control, and Eradication

replicates within, but does not produce distinct CPEin, the AS cell line (Sommer and Mennen 1997).Growth is inhibited by actinomycin D but not by5bromo2deoxyuridine (Sommer and Mennen1997, Falk et al. 1997), and the virus is most closelyrelated to other orthomyxoviruses (Mjaaland et al.1997, Krossy et al. 1999, Sandvik et al. 2000).Four major polypeptides are evident with estimatedmolecular sizes of 71, 53, 43, and 24 kDa (Falk et al.1997).

Mjaaland et al. (1997) indicated that the totalgenome of ISAv (14.5 kb) consisted of eightsegments between 1 and 2.3 kb. This geneticanalysis suggests a close relationship between ISAvand other viruses in the family Orthomyxoviridae, butthe smallest genomic segment (segment 8) is nothomologous with any other known sequence data.Development of a primer set from this segmenttherefore had significant diagnostic value. Krossy etal. (1999) further established a relationship betweenISAv and other orthomyxoviruses by examining thehighly conserved orthomyxovirid PB1 proteinencoded by segment 2. Intrafamily geneticcomparisons conducted in this manner showed thatISAv has a distant relationship with other orthomyxo-viruses and is more closely related to the influenzaviruses than to the Thogoto viruses. The relationshipto the orthomyxoviruses was further strengthened bythe demonstration by Sandvik et al. (2000) that theISAv genomic segments had conserved 3- and 5ends typical for orthomyxoviruses, and the ISAvmRNA has heterologous 5-endsindicating areplication strategy more related to the influenzaviruses than the Thogoto viruses.

On the basis of the Krossy teams geneticcharacterizations and the psychrophilic nature of thisvirus, which potentially restricts its host range topoikilothermic vertebrates, those authors proposedthat ISAv be the type species of a new genus,Aquaorthomyxovirus. The name Isavirus has beenproposed by the International Committee onTaxonomy of Viruses version 3 (http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/index.htm) for this genus, inpreference to Aquaorthomyxovirus suggested byKrossy et al. (1999).

Nucleotide variations in segments 2 and 8 wereused to differentiate Scottish isolates of ISAv fromthose of Norwegian or North American origins(Cunningham and Snow 2000, Krossy et al. 2001).Despite such differentiation, the Scottish isolate wasmore closely related to the Norwegian strain than itwas to the North American strain. These results mayinitially have indicated that geographic proximityinfluences the ISAv genotype, suggesting that distinctstrains occur on both sides of the Atlantic Ocean.However, Ritchie et al. (2001a) showed thatnucleotide sequences of an ISAv isolate obtainedfrom Atlantic salmon in Nova Scotia were moresimilar to Norwegian and Scottish strains than toisolates from neighboring New Brunswick. Althoughdifferences were not detected in the nucleotidesequences analyzed, the Nova Scotian isolate did notcause typical ISA and was, therefore, considered tobe functionally different from the Scottish andNorwegian isolates. On the basis of calculatedevolutionary mutation rates in segment 2, Krossy etal. (2001) suggested that Canadian and NorwegianISAv isolates diverged about 100 years ago, which,interestingly enough, coincided with anthropogenicmovements of salmonid fishes (particularly viatransport of sea trout), between Europe and NorthAmerica.

The virus possesses hemagglutinating as wellas fusion and receptor-destroying activity. The latteractivity has been suggested to be caused by anacetylesterase (Falk et al. 1997). Devold et al. (2001)have shown that the hemagglutinin (HA) genecontains a highly polymorphic region (HPR), whichshows sequence variation where distinct groups ofisolates predominate within certain geographic areas.Additionally, sequence analyses have been providedfor segment 3, which encodes for the nucleoprotein(NP) that has an approximate mass of 71 to 72 kd(Snow and Cunningham 2001, Ritchie et al. 2001b,Clouthier et al. 2002); for segment 4, which ispurported to be a polymerase encoding gene for theP2 protein (Ritchie et al. 2001b, Clouthier et al. 2002);for segment 6, which encodes a 3842-kd glycosy-lated protein determined to be the HA analogue(Griffiths et al. 2001, Clouthier et al. 2002, Kibenge et

http://www.ncbi.nlm

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Infectious Salmon Anemia:The Current State of Our Knowledge

al. 2002, Devold et al. 2001); and for segment 7,which possibly encodes for two matrix genesexpressing the P4/P5 proteins (Biering et al. 2002).Clouthier et al. (2002) have completed a genetic mapfor ISAv and, in addition to what has been notedabove, these authors have completed analysis ofsegments 1 and 5. Segment 1 has been shown toencode for the P1 protein and segment 5, for the47-kd glycosylated P3 protein suggested to be asurface glycoprotein.

Pathogenicity

Considerable viral replication occurs within infectedfish, and the virus may become widely disseminatedthroughout most tissues, including midkidney, headkidney, liver, spleen, intestine, gills, muscle, and heart(Jones et al. 1999a, Rimstad et al. 1999). Danneviget al. (1994) suggested that liver cells, leukocytes,and immature erythrocytes are target cells forreplication of ISAv. Further study by Nylund et al.(1996) supported the hypothesis that leukocytes maybe target cells for ISAv and showed that it canactually replicate in endothelial cells lining the bloodvessels in the ventricle of the heart, in endocardialcells, and in polymorphonuclear leukocytes. In tissueculture, the virus binds to sialic acid residues on thecell surface and fuses with endosomes andliposomes, where binding, uptake, and fusion areenhanced as pH values are decreased from 7.5 to4.5 (Eliassen et al. 2000).

Clinical signs may be evident 24 weeksfollowing infection and commonly include pale gills,ascites, enlargement of the liver and spleen,petechiae in the visceral fat, congestion of the gut,severe anemia, and mortality (Hovland et al. 1994,Thorud and Djupvik 1988, Evensen et al. 1991).Microscopic pathological changes are commonlycharacterized by renal interstitial hemorrhage andtubular necrosis, branchial lamellar and filamentalcongestion, congestion of the intestine and pyloriccecae, and perivascular inflammation in the liver(Mullins et al. 1998b, Rimstad et al. 1999). Prominentlesions are often reported in the parenchyma andvascular system of the liver, where congestion and

degeneration of hepatocytes are often followed byhemorrhagic necrosis in the latter stages of disease(Evensen et al. 1991).

Speilberg et al. (1995) concluded that lesions inthe liver may not be the sole result of an anemiabecause significant ultrastructural damage hadalready occurred before a decrease in hematocritvalues and any viral-induced disruption of thehepatocytes had been observed. These observationssuggest that the lesions in the liver may result froman impeded sinusoidal blood flow that culminates inan ischemic hepatocellular necrosis (Speilberg et al.1995). Decreases in hepatic glutathione of up to70 percent observed in diseased fish may affect thecapability of the liver to transform and excretexenobiotics from the body (Hjeltnes et al. 1992).

The development of anemia suggests thaterythrocytes may be among the most importanttarget cells of the virus. Anemia often developsrather late in the course of infection (Dannevig et al.1994), and a leukopoenia is suggested to developconcomitantly with the anemia (Thorud 1991).However, Dannevigs team demonstrated that headkidney leukocytes are infected earlier and areprobably more important than erythrocytes inreplication of the virus earlier in the infective process.Still, fish injected with the ISAv may display asuppressed leukocyte response that does notnecessarily correlate with the development oferythrocytic anemia (Dannevig et al. 1994).Suppression of immune function and development ofanemia, therefore, appear to be independent events.

Experimentally, elevated plasma cortisolconcentrations have been correlated to the severity ofanemia as measured by hematocrit values (Olsen etal. 1992). Plasma lactate may also be elevated indiseased fish (Olsen et al. 1992).

Transmission

The disease is pronounced in the marineenvironment, where it is most often transmitted bycohabitation with infected live salmon or infectedbiological materials such as animal wastes or

4


discharges from normal aquaculture operations,slaughter facilities (Vagsholm et al. 1994), andcontaminated wellboats (Shannon 1998, Murray et al.2002). Infected fish may transmit the disease weeksbefore they show apparent signs of infection. Thevirus may spread horizontally, from fish to fish, byshedding of virions from the blood, gut contents,urine, and epidermal mucus of infected salmon(Totland et al. 1996). Moreover, fish that surviveepizootics may shed viral particles for more than1 month into the surrounding water (Hjeltnes et al.1994), within which the virus is relatively shortlivedand may persist for only about 20 hours at 6 oC andup to 4 days in tissues at the same temperature(Nylund et al. 1994b). Consequently, infectedbiological materials, such as animal wastes ordischarges from aquaculture operations, slaughterfacilities (Vagsholm et al. 1994), and contaminatedwellboats (Shannon 1998, Murray et al. 2002), mayestablish better reservoirs of infection than the watercolumn alone. Blood and mucus contain especiallylarge amounts of virus and more effectively transmitthe disease than feces, plankton, and salmon lice(Rolland and Nylund 1998).

Sea lice of the species Caligus elongatus andLepeophtheirus salmonis, however, may also beimportant vectors of the virus during epidemics(Nyland et al. 1994b). There is no evidence thatscallops cocultured with Atlantic salmon eitheraccumulate the pathogen or transmit the disease(Bjoershol et al. 1999). The pathogen can betransmitted to, but has not produced disease in,freshwater brown trout (Nylund et al. 1995a), seatrout (Nylund and Jakobsen 1995), sea-run browntrout (Rolland and Nylund 1999), and rainbow trout(Nylund et al. 1997), suggesting that these fish maybecome carriers and serve as potential reservoirs ofinfection (Nylund et al. 1997). Although brown troutproduce neutralizing antibodies against ISAv within45 days after primary infection, the virus may still bepresent 7 months after infection (Nylund et al.1994a).

Clearance of the virus following experimentalinfection progresses at a greater rate in Arctic char

(Salvelinus alpinus) than in rainbow trout and browntrout. Thus, the potential for char to act as a long-term carrier of ISAv may be less than that of othersalmonids, all of which apparently clear viable virusby 40 days following injection (Snow et al. 2001).

Horizontal transmission of ISAv in fresh waterhas been achieved experimentally (Brown et al. 1998)and occurs rapidly between infected and naive smoltsin fresh water. Even under these conditions,asymptomatic smolts may remain infective to naveparr for 18 months after the original challenge(Melville and Griffiths 1999).

Vertical transmission of the virus from parent tooffspring via intraovum infection has not beendemonstrated (Melville and Griffiths 1999). Eventhough it is commonly believed that the virus is nottransmitted vertically, ISAv mortality has beenreported among first-feeding fry (Nylund et al. 1999).This scenario emphasizes the importance ofscreening brood fish and conducting proper eggdisinfection procedures to reduce contagion in earlylife stages.

Diagnostics and Detection

Viral replication and the development of CPE intissue culture are routinely used as the standard bywhich all other diagnostic and detection assays aremeasured. As already mentioned, the virus can becultured in Atlantic SHK1 cells, the CHSE214 cellline, the ASK cell line, the TO cell line, and the AScell line. The focal CPE associated with ISAv growthin CHSE214 cells suggest that this cell line couldprovide the foundation for a culture-based diagnostic.The lack of focal CPE has been viewed as adisadvantage associated with SHK1 and AS cells.Unfortunately, the CHSE214 line does not supportthe growth of all ISAv isolates (Kibenge et al. 2000b).The inability of some ISAv isolates to replicate inCHSE214 cells and the lack of distinct CPE in eitherAS or SHK1 complicate effective and consistentcultural detection of this virus. Consequently, paralleluse of both SHK1 or CHSE214 cells providesmore sensitive detection of ISAv than use of either

5


cell line alone (Opitz et al. 2000). Further develop-ment and greater availability of the ASK and TO celllines may alleviate these problems.

Nonculture-based diagnostics that detectISAv include an indirect fluorescent antibody test(Falk and Dannevig 1995a) and a reverse-transcriptasepolymerase chain reaction (RTPCR)procedure (Mjaaland et al. 1997). Furtherconfirmation has been effected by the use of a DNAprobe employing primer sets developed againstsegment 8 of the virus (McBeath et al. 2000).

Devold et al. (2000) found RTPCR to be moresensitive for detection of ISAv among carrier sea troutthan either culture or injection of suspect bloodsamples into nave fish. Furthermore, RTPCRscreens of gill mucus present an accurate andsensitive nonlethal alternative for detection of thevirus from other tissues that require necropsy(Griffiths and Melville 2000).

Production of a monoclonal antibody againstISAv enabled Falk et al. (1998) to conduct severalserodiagnostic assays, including the enzyme-linkedimmunosorbent assay (ELISA), immunofluorescentantibody staining of virus-infected cell cultures,immunoelectron microscopy of negatively stainedvirus preparations, virus neutralization assay, andhemagglutination inhibition assay.

Atlantic salmon that survive infections with ISAv(Falk and Dannevig 1995b) or are either passively(Falk and Dannevig 1995b) or actively immunized(Brown et al. 2001, Jones et al. 1999b) against thevirus develop an immune resistance against thispathogen. Recently, an indirect ELISA assay wasdeveloped to detect antibodies to ISAv in Atlanticsalmon sera (Kibenge et al. 2002). In a diagnosticsense, this assay can theoretically denote previousexposure to the pathogen among nonvaccinated fishby detection of viral-specific antibodies. The assayalso permits titration of ISAv-specific antibodies as aconsequence of vaccination. In general, the currentnonculture-based methods for routine detection andconfirmation of ISAv, in decreasing order of sensitivityand specificity, are RTPCR, antibody ELISA,immunofluorescence, and histopathologic

examination (Groman et al. 2001). It is important tonote that the phenotypic (Kibenge et al. 2000b) andgenomic (Blake et al. 1999) differences that existamong ISAv isolates may influence the use ofspecific assays.

Management

Because of the acute nature of the disease and aninability to control mortality, European EconomicCommunity countries require compulsory slaughterof infected stocks (Hill 1994). Similar eradicationprograms have been enacted in Canada (Mullins1998a). Because the virus is readily transmitted inseawater, such dissemination may readilycontaminate culture facilities within 5 to 6 km of aninfected site within a 6- to 12-month period (Eide1992). It is recommended, therefore, that culturesites be spaced no less than 56 km apart and thatwastewater from slaughter and processing facilitiesbe thoroughly disinfected (Jarp and Karlsen 1997).

Further contagion may be managed by controlof ship and personnel movements among sites,destruction of infected lots, and the closure andfallowing of contaminated sites (Murray 2001).Iodophor, chloramineT, and chlorine dioxide havebeen shown to be effective topical disinfectantsagainst ISAv when used for a minimum of 5 minutesaccording to manufacturers instructions (Smail et al.2001).

Nylund et al. (1995b) have observed greateroverall resistance to ISA among two wild strains ofAtlantic salmon than was noted in a strain used incommercial aquaculture. Because all other physicalparameters that may have affected challenge resultswere held constant, the observed patterns ofresistance were believed to result from geneticdifferences among the strains. Such differencescould theoretically be used to select for resistance toISAv (Dahle et al. 1996). The management of ISAvthrough the development of disease-resistant strainsof fish, however, is not consistent with current controlpractices that involve destruction of infectedpopulations and disinfection of contaminated sites.

6


Vaccination

Jones et al. (1999b) have shown that vaccination viaintraperitoneal injection of inactivated virus elicitedthe best protection if at least 734 degree-days hadelapsed between vaccination and challenge. Thesestudies resulted in the development of a commer-cially licensed autogenous product used withinspecific areas (McDougall et al. 2001). Protectionwas significantly improved if the viral antigen wasdelivered in an oil emulsion (Jones et al. 1999b,Brown et al. 2001). Christie et al. (2001) alsoindicated that vaccination may produce relativepercent survival values of 90 or higher (54 percentmortality among controls) for 6 months aftervaccination without significant risk of viral transmis-sion by vaccinated fish that may have becomeasymptomatic carriers. The latter research was theresult of a consortium of scientists from the Universityof Bergen, the National Veterinary Institute, andIntervet Norbio and was supported financially by theNorwegian Research Council. A multivalent vaccineincluding ISAv, infectious pancreatic necrosis virus,Vibrio anguillarum (two serotypes), V. salmonicida,Aeromonas salmonicida, and Moritella viscosaprepared in a water in oil formulation is projected forcommercial availability within Norwegian and FaroeIsland markets by early 2003. Multivalent vaccinecombinations designed for the Canadian and UnitedKingdom markets are also in development.

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Jarp, J.; Karlsen, E. 1997. Infectious salmon anaemia(ISA) risk factors in sea-cultured Atlantic salmonSalmo salar. Diseases of Aquatic Organisms 28:7986.

Jones, S.R.M.; MacKinnon, A. M.; Groman, D. B.1999a. Virulence and pathogenicity of infectioussalmon anemia virus isolated from farmed salmon inAtlantic Canada. Journal of Aquatic Animal Health 11:400405.

Jones, S.R.M.; Mackinnon, A. M.; Salonius, K. 1999b.Vaccination of freshwater-reared Atlantic salmonreduces mortality associated with infectious salmonanaemia virus. Bulletin of the European Associationof Fish Pathologists 19: 98101.

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Kibenge, F.S.B.; Lyaku, J. R.; Rainnie, D.; Hammell, K.L. 2000b. Growth of infectious salmon anaemia virusin CHSE214 cells and evidence for phenotypicdifferences between virus strains. Journal of GeneralVirology 81: 143150.

Kibenge, F.S.B.; Grate, O. N.; Johnson, G.;Arriagada, R.; Kibenge, M.J.T.; Wadowska, D. 2001.Isolation and identification of infectious salmonanaemia virus (ISAV) from coho salmon in Chile.Diseases of Aquatic Organisms 45: 918.

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Krossy, B.; Hordvik, I.; Nilsen, F.; Nylund, A.;Endresen, C. 1999. The putative polymerasesequence of infectious salmon anemia virus suggestsa new genus within the Orthomyxoviridae. Journal ofVirology 73: 21362142.

Krossy, B.; Nilsen, F.; Falk, K.; Endresen, C.; Nylund,A. 2001. Phylogenetic analysis of infectious salmonanaemia virus isolates from Norway, Canada andScotland. Diseases of Aquatic Organisms 44(1): 16.

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McBeath, A.J.A.; Burr, K. L.A.; Cunningham, C. O.2000. Development and use of a DNA probe forconfirmation of cDNA from infectious salmonanaemia virus (ISAV) in PCR products. Bulletin of theEuropean Association of Fish Pathologists 20(4):130134.

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Mullins, J. 1998. Infectious salmon anemiamanagement and control in New Brunswick.[Abstract.] In: 6th annual New England farmed fishhealth workshop; 3 April 1998; Eastport, ME, MarineTechnology Center. Orono, ME: University of MaineCooperative Extension: 13.

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13

Abstract: The Office International des Epizooties (OIE) isthe World Organization for Animal Health; it currentlycomprises 162 member countries. While representation isusually through the member countries chief veterinaryofficers, competent authorities other than the nationalveterinary services may be responsible for aquatic animalhealth in some OIE member countries.

In 1960, the OIE established the Fish DiseasesCommission (FDC) because of increasing awareness ofthe importance of international trade in fish and otheraquatic animals. In 1988, the scope of the FDC wasextended to include diseases and pathogens of molluscsand crustaceans.

The expansion of international trade in aquaticanimals and their products has called for appropriate rulesto avoid the risk of spread of communicable diseases.

Role and Function of the OIE Fish DiseasesCommission in the Field of Aquatic AnimalHealth

Tore Hstein1

Introduction

The Office International des Epizooties (OIE, WorldAnimal Health Organization)an intergovernmentalorganization headquartered in Pariswas created byan international agreement on January 25, 1924,signed in Paris by 28 countries. In May 2002, theOIE totaled 162 member countries worldwide.Representation in OIE is through national delegates,usually the chief veterinary officer of the country.However, competent authorities other than thenational veterinary services may be responsible foraquatic animal health in some member countries,and this fact makes it necessary for the veterinaryadministrations and other competent authorities tocooperate for the benefit of aquatic animal health.

Structure of the OIE

Each OIE member country appoints a delegate. Allthe delegates form the OIE International Committee,which meets once a year in Paris to hold its generalsession. The International Committee is the highestauthority within the OIE.

At the general session, the member countrieselect the president of the International Committee, as

Standardization of aquatic animal health requirements fortrade and harmonization of international aquatic animalhealth regulations are critically important to enable trade tocontinue while maintaining effective national diseasecontrol. The international aquatic animal health standardsprepared by the FDC are laid down in two importantdocuments, OIE International Aquatic Animal Health Codeand the Diagnostic Manual for Aquatic Animal Diseases.Currently, the Code and Manual specifically deal with 13diseases notifiable to the OIE and 18 other significantdiseases of aquatic animals. The diseases are classifiedinto one of these two lists on the basis of their socioeco-nomic importance, geographic range and etiology. Infec-tious salmon anemia (ISA) is currently listed under the listof other significant diseases, and both the Code andManual have chapters dealing with the disease.

1Tore Hstein is with the National Veterinary Institute inOslo, Norway.

well as members of the administrative, regional, andspecialist commissions. All these positions are heldfor 3 years.

The specialist commissions are composed ofmembers elected by the International Committee andare either OIE delegates or internationally renownedexperts from OIE member countries.

Currently, the OIE has four specialistcommissions:

The Foot and Mouth Disease and Other EpizooticsCommission (created 1946),

The Standards Commission (1949),

The International Animal Health Code Commission(1960), and

The Fish Diseases Commission (FDC) (1960).

The FDC was established to deal specificallywith the increase in fish diseases as aquacultureexpanded worldwide. As of 1988, the scope of theFDC was extended to include diseases andpathogens of molluscs and crustaceans as well. TheFDC has five members.

The OIE has these main objectives:

To ensure transparency in the animal healthsituation throughout the world, including aquaticanimal health;

To collect, analyze, and disseminate scientificveterinary information;

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To contribute expertise and encourage internationalcoordination in the control of animal diseases,including aquatic animal diseases;

Within its mandate under the Agreement onSanitary and Phytosanitary (SPS) measures of theWorld Trade Organization (WTO), to safeguard worldtrade by publishing health standards for internationaltrade in animals and animal products; and

To improve the legal framework and resources ofveterinary services in the member countries.

The principal policy of the OIE is to facilitateinternational trade in animals and animal products,including aquatic animals and their products, basedon health control and preventative measures. Thescope also covers food safety and animal welfare.

Over the years, the OIE had and still has animportant role to play in establishing a framework thatmay be used for strategic planning anddecisionmaking in OIE member countries.

Publication of Standards

The expansion of international trade in animals andanimal products including aquatic animals since the1960s has called for:

Appropriate veterinary regulations to avoid the riskof communicable diseases spreading to animals oreven to humans;

Standardization of animal health requirementsapplicable to trade, to avoid unnecessary hindrances;and

Harmonization of international animal healthregulations. (This is critically important to ensuregrowth in international trade while maintainingeffective national disease control.)

The International Aquatic Animal Health Code(OIE 2002a) (henceforth referred to as the AquaticCode) drawn up by the FDC meets theserequirements. Provisions are given as guidelines forthe preparation of veterinary regulations for importand export. This regularly updated collection ofrecommended veterinary requirements for

international trade takes into account specialconditions prevailing in various countries and offersappropriate solutions for each one.

The Aquatic Code, which was approved for thefirst time by the International Committee in May 1995(Hstein 1996), currently covers a list of 13 diseasesnotifiable to the OIE and a list of 18 other significantdiseases of aquatic animals of which the inter-national community needs to be aware. Diseaseshave been classified into one of these two lists on thebasis of their socioeconomic importance, geographicrange, and etiology.

Prior to 1995, when the first edition of theAquatic Code and the Diagnostic Manual for AquaticAnimal Diseases (OIE 2000) (henceforth referred toas the Diagnostic Manual) were adopted by the OIEInternational Committee, aquatic animal diseaseswere included in the OIE International Animal HealthCode (OIE 2002b), which covers diseases ofterrestrial animals. This way of providing recom-mendations for sanitary measures to be applied toaquatic animals held obvious drawbacks. A decisionto publish a separate Code and Manual for aquaticanimals was thus initially taken in the late 1980s. TheFDC carried out the onerous work of preparing bothtexts with a view to producing a separate set ofdocuments based on the same template as that forterrestrial animals, but bearing in mind the specificcriteria needed for aquatic animals. In addition tomaterial provided by members of the FDC,contributions have also been made by the OIEInternational Animal Health Code Commission, theOIE Standards Commission, and scientific experts invarious OIE member countries. Assistance wasprovided through comments and information neededas well as through preparation of certain chapters ondiseases for which the FDC members themselves didnot possess the necessary expertise. The end resultis thus based on international teamwork.

Not all countries will be able to comply witheach of the specifications detailed in the AquaticCode and Diagnostic Manual; probably only a fewcountries will have the necessary resources. Inaddition, many countries may still have concerns that

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Role and Function of the OIE Fish Diseases Commissionin the Field of Aquatic Animal Health

they would like to see resolved before subscribing toall the principles given in the Aquatic Code, namely,zoning principles, health certification, etc.

The Aquatic Code sets out general principlescovering:

Definitions,

Notification systems,

Veterinary ethics and certification for internationaltrade,

Import risk analysis,

Import/export procedures,

Contingency plans,

Diseases notifiable to the OIE (fish, molluscs, andcrustaceans),

Other significant diseases (fish, molluscs, andcrustaceans),

Health control and hygiene, and

Model international aquatic animal healthcertificates approved by the OIE.

Currently, the FDC is preparing a chapter onfallowing of aquaculture enterprises. This chapterhas not yet been approved by the OIE InternationalCommittee.

Notifications andEpidemiologic Information

The urgency of dispatching information variesaccording to the nature of the disease. The OIE hasdevised a warning system whereby membercountries can take action rapidly should the needarise. Countries are required to notify the CentralBureau within 24 hours if there is/are

A first occurrence or recurrence of a diseasenotifiable to the OIE if the country or zone waspreviously considered to be free of that particulardisease;

The emergence of new important findings or aprovisional diagnosis of diseases notifiable to the OIE

that are of epidemiologic significance to othercountries; or

New findings (for disease not notifiable to the OIE)that are likely to have exceptional epidemiologicsignificance to other countries.

The OIE immediately dispatches the incomingdata by telex, fax, or electronic mail directly tomember countries at risk and in weekly announce-ments (in Disease Information) to other countries.

In addition to this alert system, informationreceived from member countries is distributed on aperiodical basis in the monthly Bulletin, the annualWorld Animal Health Yearbooks, which provideannual animal health statistics and give data on theoccurrence of diseases in each member country andthe annual Animal Health Status reports for all OIEmember countries.

Although the responsibility for aquatic animalhealth in many OIE member countries lies withcompetent authorities other than the veterinaryadministration, nevertheless, within the OIE system,the veterinary services have the responsibility fordisease reporting in conjunction with the competentauthority in a given country. Thus, close cooperationbetween the veterinary services in a given countryand the responsible authority for aquatic animalhealth is strongly needed.

Veterinary Ethics andCertification for InternationalTrade

There may be different philosophies and opinions inregard health certification, ethics, etc., in differentcountries, but the Aquatic Code describes basicprinciples that should be taken into account to ensurethat trade is unimpeded and that such trade does notconstitute a risk to aquatic animal health. Informationon the aquatic animal health situation worldwide isthus important in order to diminish the risk of diseasetransfer through international trade in aquatic animalsand their products. Certification must be based onthe strictest possible ethical rules.

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The chapters in this section of the Aquatic Codepresent the general requirements and principles ofcertification to be followed.

Import Risk Analysis

Any importation of aquatic animals or relatedproducts may involve a risk of disease transfer to theimporting country. The Aquatic Code chapter onimport risk analysis provides an objective anddefensible method for assessing risks associatedwith importation. This basis enables the importingand exporting countries to have productivediscussions on problems associated with thepotential risks.

Import and Export Procedures

In the context of import and export, it isimportant to have general arrangements fortransportation of aquatic animals. The chapters inthis section of the Aquatic Code providerecommendations for transport and aquatic animalhealth measures before, during and upon arrival, forfrontier posts in importing countries as well asmeasures concerning international transfer ofpathological material and biological products.

Contingency Plans

A number of diseases pose a threat to aquacultureas well as to wild stocks of aquatic animalsworldwide; therefore, such diseases may causesignificant losses if introduced into countries wherethey are not established. Bearing this in mind, alldisease control should be based on a legislativeframework that includes contingency plans. Acontingency plan can be defined as an establishedplan that is designed to have a rational approach foractions to be taken if emergency situations occur andin which all types of required actions should havebeen considered and described in advance. TheAquatic Code gives guidelines for contingencyplanning.

OIE International AquaticAnimal Health Code: Listingof Pathogens and Diseases

In the International Animal Health Code, notifiablediseases are divided into Lists A and B on the basisof their seriousness. In the Aquatic Code, asexplained before, aquatic animal diseases areclassified as either diseases notifiable to the OIE orother significant diseases.

Diseases and pathogens are included in theAquatic Code according to the following basicconsiderations: resistance or response to therapy,geographic range, and socioeconomic importance.The list of diseases and pathogens considered forinclusion in the Aquatic Code is currently restricted tothose affecting fish, molluscs, or crustaceans (table1). Proposals for diseases to be listed may comefrom member countries or from the FDC, andthorough discussions take place before a newdisease is actually added to either list. Similarprocedures are followed for deletion of diseases fromthe lists.

Categorization of diseases to be listed is, ofcourse, open to debate, and opinions on whichdiseases should be listed vary greatly due to differentviews on the significance and importance of a givendisease. For several years, the FDC has beenworking to provide a disease categorization systemthat objectively classifies diseases for listing. At theFDC meeting in June 2002, the Commissionproposed a set of criteria suitable for listing aquaticanimal diseases, and this has been sent to membercountries for comments (table 2). The comments willbe considered in relation to the OIEs work on newprocedures for disease notification for terrestrial andaquatic animal diseases. Until the new procedureshave been adopted, there will be no changes to thecurrent listed diseases.

Infectious salmon anemia (ISA) was firstbrought to the attention of the OIE in the early 1990sbecause there was a need for a common scientificname for the disease. Until then, the disease wasreferred to by numerous different names in published

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papers. The OIE recognized that disease and namedit ISA in 1990.

When preparing the first edition of the AquaticCode, the FDC concluded that in addition to the list ofdiseases notifiable to the OIE, a waiting list shouldbe established for diseases that at a later stageshould either be listed as notifiable or should beremoved from consideration. ISA was put on thiswaiting list in 1992 and included in the list of other

Table 1Diseases of aquatic animals

Diseases Notifiable to the OIE

Fish DiseasesEpizootic hematopoietic necrosisInfectious hematopoietic necrosisOncorhynchus masou virus diseaseSpring viremia in carpViral hemorrhagic septicemia

Molluscan DiseasesBonamiosis (Bonamia exitiosus, B. ostrea, Mikrocytos roughley)MSX disease (Haplosporidium nelsoni)Marteiliosis (Marteilia refringens, M. sydneyi)Mikrocytosis (Mikrocytos mackini)Perkinsosis (Perkinsus marinus, P. olseni/atlanticus)

Crustacean DiseasesTaura syndromeWhite spot diseaseYellowhead disease

Other Significant Diseases in Fish, Molluscs, and Crustaceans

Fish DiseasesChannel catfish virus diseaseInfectious pancreatic necrosisInfectious salmon anemiaViral encephalopathy and retinopathyRed sea bream iridoviral diseaseWhite sturgeon iridoviral diseaseBacterial kidney disease (Renibacterium salmoninarum)Enteric septicemia (Edwardsiella ictaluri)Piscirickettsiosis (Piscirickettsia salmonis)Epizootic ulcerative syndromeGyrodactylosis (Gyrodactylus salaris)

Molluscan DiseasesSSO disease (Haplosporidium costale)Withering syndrome of abalone (Candidatus Xenohaliotiscaliforniensis)

Crustacean DiseasesCrayfish plague (Aphanomyces astaci)Infectious hypodermal and haematopoietic necrosisSpawner-isolated mortality virusSpherical baculovirosis (Penaeus monodon-type baculovirus)Tetrahedral baculovirosis (Baculovirus penaei)

significant diseases when that list was created in1993. Thus, ISA was on the list of other significantdiseases in the 1995 edition of the Aquatic Code.ISA was placed on this list and not on the list ofdiseases notifiable to the OIE because, at that time,ISA was not yet sufficiently defined. Its etiology wasnot understood well enough, and approved diagnosticmethods were not available. On more recentoccasions, the question of listing ISA as a notifiabledisease has been raised, but it has been decided thatno change in listing should be effected until a newnotification system for aquatic animal diseases hasbeen approved.

As stated previously, the current notificationsystem requires that new findings of a nonnotifiabledisease such as ISA in aquatic animals shall bereported to the OIE immediately if it is of exceptionalepidemiologic significance. ISA falls into thiscategory, and occurrence of this disease should bereported to the OIE immediately when ISA isdiagnosed in a country for the first time. Table 3 liststhe OIE member countries that have reported ISA orISA virus (ISAv).

Health Control and Hygiene

Health control and hygiene prior to internationaltrade in live aquatic animals and their products is alsoan important issue. This section of the Aquatic Codeprovides guidelines for hygienic precautions, such asthe destruction of pathogens through disinfectionprocedures in farms producing fish, molluscs, orcrustaceans. This section is currently being updatedfor the next edition of the Aquatic Code. Further-more, a general chapter on procedures fordestruction of carcasses in connection with anoutbreak of disease is in preparation.

Model International Aquatic AnimalHealth Certificates

The Aquatic Code contains five different modelhealth certificates that standardize certificationpaperwork worldwide. The certificates arecontinuously being improved following commentsreceived from OIE member countries.

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Table 2Proposed criteria for listing and for urgentnotification of aquatic animal diseases (June 2002)listing criteria

Parameters that support a listing Explanatory notes

Consequences Where it occurs, the disease has been shown to cause The disease generally leads to losses in susceptible2(any one suffices) significant production losses due to morbidity1 or species, and morbidity or mortality is related primarily

mortality on a national or multinational or (zonal regional) to the agent and not to management or environmentallevel. factors.

The disease has been shown to, or is strongly See above.suspected to, negatively affect wild aquatic animalpopulations that are an asset worth protecting.

The agent is of public health concern.

Spread Infectious etiology of the disease is proven.(either of the firsttwo plus the third An infectious agent is strongly associated with the Infectious diseases of unknown etiology can haveand fourth) disease, but the etiology is not yet known. equally high-risk implications as those diseases where

the infectious etiology is proven. While diseaseoccurrence data are gathered, research should beconducted to elucidate the etiology of the disease andthe results be made available within a reasonable periodof time.

Potential for international spread, including via live Under international trading practices, the entry andanimals, their products, and inanimate objects. establishment of the disease is likely.

Several countries or zones are free of the disease Free countries or zones could still be protected. Listingbased on the recommendations of the Code and of diseases that are ubiquitous or extremely widespreadManual. would render notification infeasible; however, individual

countries that run a control program on such a diseasecan demand its listing, provided that they haveundertaken a scientific evaluation to support theirrequest. Examples may be the protection of broodstockfrom widespread diseases, or the protection ofthe last remaining free zones from a widespreaddisease.

Diagnosis A repeatable, robust means of detection or A diagnosis test should be widely available, or hasdiagnosis exists. undergone a formal standardization and validation

process using routine field samples (see OIEDiagnostic Manual for Aquatic Animal Diseases).

Urgent Notification

Listed diseases

First occurrence or recurrence of a disease in a country or zone of a country if the country or zone of the country was previously consid-ered to be free of that particular disease

Occurrence in a new host species

New pathogen strains or new disease manifestation

Potential for international spread of the disease

Zoonotic potential

Nonlisted diseases

Emerging disease or pathogenic agent if there are findings that are of epidemiologic significance to other countries

1`Morbidity includes, for example, loss of production due to spawning failure.2 Susceptible is not restricted to susceptible to clinical disease but includes susceptible to covert infections.

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Table 3Countries having reported the detection ofISA and/or ISA virus

Year of firstCountry detection Region Species

Canada 1997 (1996) New Brunswick, Atlantic salmonNova Scotia,Cape BretonIsland,MagaguadavicRiver

Chile 2001 Region X and XI Coho salmon

Faroe 2000 Streymoy, Atlantic salmonIslands Eysturoy, Kunoy,[Denmark] Bor oy, Su uroy,

(10 differentlocations)

Ireland 2002 County Mayo, Rainbow troutwestern Ireland

Norway 1984 Several counties Atlantic salmon

United 1998 Scotland, Atlantic salmonKingdom including

Shetland Islands

United 2001 Maine Atlantic salmonStates

Diagnostic Manual for AquaticAnimal Diseases

In accordance with the current listed diseases in theAquatic Code, the FDC has prepared pertinent,updated chapters in the Diagnostic Manual forAquatic Animal Diseases. In addition to updateddiagnostic chapters on the listed diseases, theDiagnostic Manual provides a general basis forhealth surveillance or control programs for fish,molluscs, and crustaceans. Chapters on qualitymanagement in veterinary diagnostic laboratoriesand principles of validation of diagnostic assays forinfectious diseases are also included. Theseimportant chapters were originally prepared for theOIE Manual of Standards for Diagnostic Tests andVaccines (for diseases of mammals, birds, and bees),but because the principles are the same fordiagnostic work in aquatic animals, the FDC adaptedthe chapters into the Diagnostic Manual for AquaticAnimal Diseases.

The Diagnostic Manual consists of the followingsections:

General provisions (definitions, qualitymanagement in veterinary diagnostic laboratories,principles of validation of diagnostic assays forinfectious diseases);

Separate diagnostic chapters for diseases offish, molluscs, and crustaceans; and a

List of reference laboratories and collaboratingcenters for diseases of fish, molluscs, andcrustaceans.

A comprehensive approach to health control inaquatic animals requires many elements, such as:

Assessment and maintenance of health status;

Sampling, screening, and diagnostic methods;

Verification of diagnoses;

Eradication procedures; and

Constraints of restocking in open waters andfarming facilities.

Each chapter in the Diagnostic Manual iswritten by one or more distinguished experts in thefield, based on the outline given above. Thesechapters describe the latest methodology for thediagnosis of the disease in question.

The Diagnostic Manual also sets standards forscreening and diagnostic methods for diseases,which may be applied in any diagnostic laboratoryworking with diseases of aquatic animals. In additionto the more conventional methods for isolation andidentification of a putative disease agent using cellcultures, culture media for bacteria and fungi, indirectfluorescent antibody test (IFAT), enzyme-linkedimmunosorbent assay (ELISA), bacterial isolationand identification, histology, immunohistochemistry,and standard parasitological methods, more recentlydeveloped techniques, such as the polymerase chainreaction (PCR), are described for diagnosticpurposes for many of the OIE listed diseases.

The FDC is currently amending all thediagnostic chapters in the Diagnostic Manual. In thenew diagnostic chapter for ISA, the FDC proposes aminimum set of criteria for suspicion and verification

ot ot

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of the disease. These criteria refer to reasonablegrounds for suspecting fish of being infected withISAv and the steps that competent authorities shouldfollow to verify the presence or absence of ISA.

The proposed criteria for suspicion follow. Thepresence of ISA should be suspected if any of thecriteria in (a) through (e) are met:

(a) The presence of postmortem findings consistentwith ISA, as described in section 2.1. of the ISAdiagnostic chapter, with or without clinical signs;

(b) Isolation and identification of ISAv in cell culturefrom a single sample from any fish on the farm asdescribed in part 2.2. of the ISA diagnostic chapter;

(c) Reasonable evidence of the presence of ISAvfrom laboratory tests such as IFAT (2.3.1.) and RTPCR (2.3.2.);

(d) The transfer of live fish into a farm where thereare reasonable grounds to suspect that ISA waspresent at the time of the fish transfer; or

(e) Where an investigation reveals other substantialepidemiologic links to farms with suspected orconfirmed cases of ISA.

If immediate investigations do not confirm or rule outthe presence of ISA, suspicion of ISA can officially beruled out when, following continued investigationsinvolving at least one clinical inspection per month fora period of 6 months, and no further significantevidence for the presence of ISA is obtained.

Confirmation of ISA

The presence of ISA is officially confirmed if any oneof these three criteria has been met.

Clinical signs and postmortem findings of ISA inaccordance with the criteria described in section2.1.1., 2.1.2., and 2.1.3. of the ISA chapter in theDiagnostic Manual are detected and ISAv is detectedby one or more of the following methods:

(a) Isolation and identification of ISAv in cell culturefrom at least one sample from any fish on the farm

as described in section 2.2. of the ISA chapter inthe Diagnostic Manual;

(b) Detection of ISAv in tissues or tissuepreparations by means of specific antibodiesagainst ISAv (e.g., IFAT on kidney imprints) asdescribed in part 2.3.1. in the ISA chapter in theDiagnostic Manual; or

(c) Detection of ISAv by means of RTPCR by themethods described in section 2.3.2. of the ISAchapter in the Diagnostic Manual.

Isolation and identification of ISAv in two samplesfrom one or more fish at the farm tested on separateoccasions using the method described in section 2.2.of the ISA chapter in Diagnostic Manual.

Isolation and identification of ISAv from at least onesample from any fish on the farm using the describedmethod in Diagnostic Manual with corroboratingevidence of ISAv in tissue preparations from any fishon the farm using either IFAT or PCR as described inthe Diagnostic Manual.

If the principles given above are approved bythe OIE International Committee during its generalsession in 2003, similar criteria will most likely beprepared in consistent manner for the other OIE-listed diseases.

OIE Reference Laboratoriesand Collaborating Center forDiseases of Fish, Molluscs,and Crustaceans

The Diagnostic Manual also lists the OIE referencelaboratories and collaborating center for aquaticanimal diseases, including the name of theresponsible reference expert. Currently there are22 reference laboratories for diagnosis, control,research, and training for the OIE-listed diseases inaquatic animals as well as one collaborating centerthat cov

international response to infectious salmon anemia: prevention

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