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Transcript of Shrimp Diseases
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Congratulations to the OIE for theadoption of Resolution 18/2011, officially recognizing
that all 198 countries of the world withrinderpest-susceptible animal populations are free of
the disease (79th General Session of the OIE, 22-27
May 2011)
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Outline
Introduction to Aquatic Animal Diseases
Current Status of ISA
Current Trends in Lab Diagnosis and PathogenSurveillance
Challenges Faced by Diagnostic Labs forAquatic Animal Diseases
Conclusions
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Aquaculture is the worlds fastest-growing animal-foodproducing sector Annual growth rate of 8.4% since 1970; reached 65.8 million tonnes
in 2008
Aquaculture now accounts for almost half of the total fish supply forhuman consumption, and is likely to continue increasing.
FAO predicts that by 2030 there will be an additional 2 billion people tothe world population; & an additional 37 million tonnes of fish/year willbe needed to maintain current levels of fish consumption.
China supplies 61.5% of global aquaculture production(29.5% from rest of Asia)mostly Carp 3.6% from Europe & 2.2% from South Americasalmonids
1.5% from North Americaeven production across the speciesgroups
1.4% from Africatilapias
0.3% from Oceaniashrimps & prawns
Aquatic Animal Diseases
(global trends & spread & emerging threats)
Hall et al., 2011. Blue Frontiers: Managing the Environmental Costs of Aquaculture. The WorldFish Center, Penang, Malaysia
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Increased aquaculture production through translocation of cultured live animals or shipment of eggs to
new destinations
Expanding range of new farmed aquatic animal species
such as Atlantic halibut, Arctic char, sablefish, Atlantic cod,crustaceans, molluscs
New production approaches such as integrated multi-trophic aquaculture
Improved diagnostic & surveillance efforts the more you look (with better technology) the more you find
Factors leading to the discovery of new & emerging
aquatic animal diseases
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The spread of diseases is the most feared threat to aquaculture. It is amatter of global concern especially with increased trade & movement oflive aquatic animals & their products across national borders. Examplesinclude:
White spot syndrome disease in shrimp spread to 22 countries viatrade in post-larvae
Taura syndrome spread from Americas to Asia via live shrimpmovements
Gyrodactylus salaris spread from Sweden to Norway via livejuvenile salmon for stock enhancement
First case of Sleeping disease in UK was linked to imported troutfillets
EHN virus spread from Germany to Finland via live farmed
sheatfish imports First cases of SVC in Switzerland, USA, Denmark were linked to koicarp imports
Koi herpesvirus has been linked to international koi carp trade
ISA outbreaks in Atlantic salmon in Chile in 2007: ISA virus wasmost similar to isolates from Norway.
Aquatic Animal Diseases
(global trends & spread & emerging threats)
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Flow of Biological Aquatic Material to Chile
Modified from M. Godoy & F. Kibenge, November 2008
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One of the most important challenges facing aquaculture is ability to
control disease
Disease constitutes the largest single cause of economic losses inaquaculture
Value of world aquaculture production in 2008: USD 98.4 billion
Global estimate of disease losses to aquaculture by World Bank (1997)was ~ USD 3 billion
Current estimates suggest between 1/3rdto 1/2 of farmed fish & shrimpsare lost to poor health management before they reach marketable size
(Tan et al., 2006).
Some endemic diseases remain a challenge for aquaculture. For example: SRS (Piscirickettsia salmonis) in Chile remains one of the most important
causes of mortality in trout and Coho salmon in seawater, & was in Atlanticsalmon before June 2007; It is the main cause of antibiotic use.
Pancreas diseases & sea lice in Norway, and Caligus in Chile are huge sanitary
problems.
Aquatic Animal Diseases
(global trends & spread & emerging threats)
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Aquatic Animal Diseases (global trends & spread & emerging threats)
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Viral haemorrhagic septicaemia (VHS)
Pancreas disease (PD)
Cardiomyopathy syndrome (CMS)
Heart and skeletal muscle inflammation (HSMI) Infectious salmon anaemia (ISA)
Aquatic Animal Diseases
(global trends & spread & emerging threats)
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Global distribution of viral haemorrhagic septicemia virus
Dark: VHSV isolated from marine species
Light: classical freshwater rainbow trout pathogenic VHSV isolates
?
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SAV1
SAV2 FW
SAV2 SW
SAV3
SAV4
SAV5
SAV6
Salmon alphaviruses
From Intervet Schering-Plough Animal Health PD Technical Manual
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12
5Sogn og Fjordane
Hordaland
Rogaland
1Mre og Romsdal
5
Nord-Trndelag 1
PD outbreaks in Norway in Year 2011
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Prevalence of Cardiomyopathy syndrome (CMS) &
Heart and skeletal muscle inflammation (HSMI)
CMS recorded
CMS suspected
HSMI recorded
HSMI suspected
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Current status of ISA
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First-time Outbreaks of ISA
*
**
*
*
2000
1998
2009
2001
1996
2009
2007*
*
1984
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ISAV
North American
European
2 basic genotypes/
serotypes
real-European
European-in-North America
HPR20
HPR21
EU-G1
2-to-3 genogroups
EU-G2
EU-G3
EU-G2
Nylund et al., 2007Kibenge et al., 2007Kibenge et al., 2001
ISAV Strain identification
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Fuente
Prevalence of ISA outbreaks in Norway (1984 to August 2010)
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Update on ISA situation in Scotland:
ISAV European genotype
First ISA outbreak in 1998. Disease was erradicated in 1999
ISAV from different sites was 100% identical on segment 8,suggesting a single point source
ISAV HPR7b
Suspected case in November 2004 ISAV HPR0
Second ISA outbreak in southwest Shetland in January 2009 Infection started after June 2008
ISAV HPR10; from unknown source
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Update on ISA situation in Faroe Islands:
ISAV European genotype
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Update on ISA situation in Chile:
ISAV European genotype
First ISA outbreak occurred in June 2007 on Atlanticsalmon seawater farm site in central Chilo in Region Xfollowing recovery from an outbreak of Pisciricketsiosis.
ISAV was most similar to isolates from Norway. it acquired mutations in surface envelope proteins predominant pathogenic type was ISAV HPR7b until March
2010
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Recent introduction of ISAV to Chile: was it
single or multiple introductions?
Single introduction ofChile 1 strain with noinsert in segment 5 toFarm X in 1996(Kibenge et al., 2009)
Mutation occurred on Farm Xresulting in Chile 3 strain with insert insegment 5, e.g., Cottet et al., (2010)isolate ISAV752_09.
Spread of closely related ISAV strains withinsert in segment 5 (Chile 2 to Chile 7strains)
Multiple introductions asChilean Ancestor 1 andChilean Ancestor 2(Cottet et al., 2010)
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Phylogeny of concatenatedF and HE genes fromGenotype I:Genogroup 2Clade 2.2 (Norway II) ISAV
isolates
new Chile isolates,Clade 2.2.2.1.2 (Chile)
Norway 1997 isolates,Clade 2.2.2.1.1 (Norway)
Norway HPR0 isolates
EU-G2 isolates: Clades 2.2.1.1. & 2.2.1.2Clade 2.2
Clade 2.2.1
Clade 2.2.2
Clade 2.2.2.1
EU-G1 isolates
Cottet et al., 2010
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Prevalence of ISAV (virulent and HPR0) positive cases in Chile
(July 2007 to April 2011)
21 1
3 4
2 2 21
2
34
2
7
3
9
3
7
3
6
7
8
13
17
20
21
24
22
19
4
5
4
9
2 4
2 32 1
2
1
1
1
0
5
10
15
20
25
Numerode
Centros
Meses
Virulentos
HPR0
260Cases
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Update on ISA situation in Canada and USA:
ISAV North American & European genotypes
First ISA outbreak outside of Norway wasin New Brunswick, Canada, in 1996; virusmight have been present by 1995
A single ISA outbreak occurred in Nova
Scotia, Canada, in 2000.
ISA first confirmed in Maine, USA, in2001
A single ISA outbreak occurred in Prince
Edward Island, Canada, in 2009.
ISAV HPR0 has now completely replacedthe virulent ISAV in both New Brunswickand Maine.
Farm site
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First-time ISAV HPR0 Reports
*
**
*
*
2006
2002
2004
2004
2008 *
*
2002
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ISAV HPR0 Characteristics
ISAV without any deletion/insertion in HPR is designated HPR0 to indicate full-length HPR
All ISAV isolated to date from clinical disease have deletions in HPR relative toHPR0. HPR0 is considered the putative ancestral virus.
NH2- -COOH
HPR
Transmembrane
domain
HE
ProteinORF
Cytoplasmic
tail
N-terminal
region
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ISAV HPR0 viruses: Challenges
Do not grow in cell culture; no CPE
How can they be used in experimental infections? Is there a reverse genetics system for ISAV?
Do not cause disease; are non-pathogenic Can they cause sub-clinical infection (e.g., immunosuppression)?
Are they a risk factor for developing ISA? Are ISAV HPR0 viruses immunogenic? Can they interfere with or boost ISAV vaccines?
Can only be detected by RT-PCR followed by sequencing;known only through genomic sequence fragments Can cause diagnostic confusion. A challenge for prevention &
control programs.
Can complicate surveillance efforts.
Can increase costs of depopulation control programs.
Are there other reservoirs of HPR0 viruses?
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focusing primarily on the nucleic acid-basedassays and their utility for pathogen discovery,surveillance, and confirmatory diagnosis
Current trends in laboratory diagnosis and
pathogen surveillance
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Historical overview of laboratory diagnosis from culture-based assays to
nucleic acid-based diagnosis
Historically, lab diagnosis has relied on culture of pathogen and/or measurement ofantibodies in sera.
Early detection of infection has relied on development of rapid & sensitive
diagnostic methods.
There is a need for assays that can allow unbiased analysis of pathogens in a
sample, since differential diagnosis is difficult in early infection before appearance of
clinical signs.
From http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521downloaded January 03, 2011.
http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521http://www.genengnews.com/gen-articles/improving-diagnostics-related-informatics/3521 -
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CONFIRMATORY
SCREENING/SURVEILLANCE
DISCOVERY
BIASED
UNBIASED
NUCLEIC ACID-
BASED ASSAYS
Singleplex PCR/RT-PCR
Multiplex PCR/RT-PCR;
Luminex;
High density qPCR/RT-qPCR;Microarrays
Deep sequencing
Laboratory Diagnostic Tests
PATHOGEN DETECTION
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Statistically relevant disease surveillance & monitoring requires largenumbers of aquatic animals reliable detection of pathogen is difficult if clinically sick aquatic animals are
not available or only low percentage of aquatic animals is infected
constant need to increase throughput (automation, miniaturization, etc)
effective monitoring requires quantitative methods that inform on pathogen
load in aquatic animals or the environment Need cost-effective, fast, highly sensitive & specific methods that allow
unbiased pathogen detection
No perfect method. Assay development is never-ending
Prevalence of aquatic animal diseases change depending on: time of year & water temperature (Plumb 1999)
success in disease management Need for QA (Ring tests)
effective way in establishing national/international cut-offs of (highlysensitive) nucleic acid-based assays.
General challenges faced by diagnostic labs
for aquatic animal diseases
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Turnaround time of diagnostic laboratory
Distance from farm site to diagnostic laboratory
Quality of sample
Specific diagnostic challenges
Farm sites
Diagnostic labs
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Norway: HSMI, PD, CMS, Sea lice
Chile: SRS, BKD, Caligus, ISAV-HPR0
Specific diagnostic challenges:
- mixed infections
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Specific diagnostic challenges:
- Standardization of diagnostic tests
Positive controls are expensive & not easy to get
Cut-off determination is complicated (criteria not defined; could be
related to culture of pathogen or to clinical situation of the aquatic
animal or farm, etc)
Case definition may be different for different countries.
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Aquaculture is important now and in the future as aprincipal source of animal protein for human consumption
Aquatic animal disease is part and parcel of aquaculture Intensification of aquaculture is accompanied by increased stress
resulting in a significant proportion of stock becoming infected.
Unbiased pathogen detection from carrier aquatic animals is
essential for effective disease control in the global aquacultureindustry.
Improved diagnostic & surveillance efforts will result in thediscovery of new & emerging aquatic animal diseases.
Nucleic acid-based assays, particularly multiplex assays such asmicroarrays are well suited for pathogen detection, typing, &
discovery in aquatic animal populations Diagnostic labs for aquatic animal diseases have challenges
inherent in the nature of the aquaculture industry and require theinvolvement of the OIE.
Conclusions
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Thank you