shrimp diseases

8/13/2019 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.




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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.




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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)




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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:



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Update on ISA situation in Chile:


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.

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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

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