-
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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The opinions expressed by individuals in this report do
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Mention of companies or commercial products does not
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provide specific information.
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.
i
-
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.
ii
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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
iii
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
iv
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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
v
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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
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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
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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
ix
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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
x
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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
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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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2
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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3
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
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4
International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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
Infectious Salmon Anemia:The Current State of Our Knowledge
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.
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6
International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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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Snow, M.; Cunningham, C. O. 2001. Characterizationof the
putative nucleoprotein gene of infectioussalmon anemia virus
(ISAV). Virus Research 74:111118.
Snow, M.; Raynard, R. S.; Bruno, D. W. 2001.Comparative
susceptibility of Arctic char (Salvelinusalpinus), rainbow trout
(Oncorhynchus mykiss) andbrown trout (Salmo trutta) to the Scottish
isolate ofinfectious salmon anaemia virus. Aquaculture
196:4754.
Sommer, A. I.; Mennen, S. 1997. Multiplication andhaemadsorbing
activity of infectious salmon anaemiavirus in the established
Atlantic salmon cell line.Journal of General Virology 78:
18911895.
Speilberg, L.; Evensen, .; Dannevig, B. H. 1995. Asequential
study of the light and electron microscopicliver lesions of
infectious anemia in Atlantic salmon(Salmo salar L.). Veterinary
Pathology 32: 466478.
Thorud, K. E., 1991. Infectious salmon anemia.
D.Sc.dissertation. Olso, NO: Norwegian College ofVeterinary
Medicine.
Thorud, K. E.; Djupvik, H. O. 1988. Infectious salmonanemia in
Atlantic salmon (Salmo salar L.). Bulletinof the European
Association of Fish Pathologists 8:109111.
Totland, G. K.; Hjeltnes, B. K.; Flood; P. R. 1996.Transmission
of infectious salmon anemia (ISA)through natural secretions and
excretions frominfected smolts of Atlantic salmon Salmo
salar.Diseases of Aquatic Organisms 26: 2531.
Vagsholm, I.; Djupvik, H. O.; Willumsen, F. V.; Tveit,A. M.;
Tangen, K. 1994. Infectious salmon anaemia(ISA) epidemiology in
Norway. Preventive VeterinaryMedicine 19: 277290.
Wergeland, H. I.; Jakobsen, R. A. 2001. A salmonidcell line (TO)
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of AquaticOrganisms 44: 183190.
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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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International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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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International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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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17
Role and Function of the OIE Fish Diseases Commissionin the
Field of Aquatic Animal Health
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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International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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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19
Role and Function of the OIE Fish Diseases Commissionin the
Field of Aquatic Animal Health
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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International Response to Infectious Salmon Anemia:Prevention,
Control, and Eradication
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