Australia’s Disease Status and Risk Pathways Dr Matt Landos 1 BVSc(HonsI)MANZCVS Dr Christine Huynh BVSc Future Fisheries Veterinary Service Pty Ltd

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Australia’s Disease Status and Risk

PathwaysDr Matt Landos1 BVSc(HonsI)MANZCVS

Dr Christine Huynh BVSc Future Fisheries Veterinary Service Pty Ltd

Prawn Superpowers Summit31 July 2012, QLD

Australian prawn production

Farmed Industry value•1996: $35 million•2007: $45 million (monodon(65%) and merguiensis(35%)).•2012: $80 million• Wild harvest industry ~ 20,000t

•Limited new farm sites due to social factors and environmental policy.

•Potential for existing farms to increase production through further intensification of production.

•With intensification comes increased disease risk.

•Control of GAV on some farms has been associated with improved production per hectare


World disease status- production impact

2011: World production fell ~20% to 2.5 million tonnes with disease and unfavorable weather

Thailand: production forecast to increase to 700 000 t in 2012India: production of black tiger may decline 40–50 percent to 60 000–70 000 t. Vannamei producers, could increase 30% to 100,000 tonnes in 2012. Malaysia: vannaemi production down 43% in 2011Vietnam: Supplies of vannamei are also expected to increase Diseases including EMS, WSSV and IMNV are major threats to production targets and remain the source of substantial losses to the industry outside of Australia

World diseases causing losses

China: WSSV and Early Mortality Syndrome (EMS) or Acute Hepatopancreatic necrosis syndrome (AHPNS). 2011: 80% loss from Guangdong, Hainan, Guangxi, and FujianThailand: EMS, flooding, WSSV decreased productionVietnam: Increased WSSV, EMS ($70 million loss in 2011), Vibriosis and IMNV, antibiotic residue, environmental and salination problemsIndonesia: Ongoing problems with IMNVMalaysia: WSSV problems in 2011 and in cooler weather, EMS

Diseases detected in Australia

Gill-associated virus (GAV)

Monodon Baculovirus (MBV)- [Spherical baculovirus]

Hepatopancreatic parvovirus (HPV) =PmergDNV densovirus

Spawner isolated mortality virus (SMV)

Mourilyan Virus (MOV)

White tail disease – Macrobrachium rosenbergi nodavirus (MrNV)


Diseases not detected in the ‘lucky country’ -

Australia White Spot Disease (WSSV)

Yellowhead (YHV)

Taura Syndrome (TSV)

Infectious myonecrosis virus (IMNV)

Early mortality syndrome (EMS)

Loose shell syndrome

Abdominal Segment Deformity Syndrome

Monodon slow growth syndrome (MSGS)


GOOD MANAGEMENT

AQIS IRA- import testing green prawns

Remote location of farms to Asia

No live prawn imports

Vertical farm integration- limited PL & equipment sharing

High quality feed, pond management

Gill- Associated Virus

Visual signs: Biofouling with ectoparasites, reddening of tail fan Birds feeding on sick shrimp, shrimp coming to

edge of the pond, decreased feed intake Shortened antennae


Gill-Associated Virus (GAV)= Mid Crop Mortality

Syndrome Outbreaks with higher

viral load post stocking + stress= mortalities

High viral load at 4 weeks post stock = 95% chance of disease outbreak,…. Cull recommended

Chronic low grade losses in lesser affected ponds


Asymptomatic carriers common from all east coast wild caught spawners

Gulf stock low risk- appear to be free from GAV at this time

Transmission: horizontal-water, ingestion; Vertical transmission also possible from broodstock to larvae

Monodon Baculovirus (MBV)

Clinical signs: Emaciation- go dark in colour, not feeding, lethargic, gill shell

fouling Pale hepatopancreas

Transmission: horizontal- via water or cannibalism

Washing nauplii in disinfected water can manage infecti

Impression smear techniques available for rapid diagnosis


Hepatopancreatic parvovirus

Australian strain named Penaeus merguiensis densovirus (La Fauce, Elliman & Owens 2007)

Associated with stunting, and occasional mortality outbreak in P. Merguiensis

Damages gut lining of shrimp

Desirable to stock low viral load prawns


Spawner Isolated Mortality virus

Northern Australian prawns affected in the mid- 1990s, affecting P.monodon and P.merguiensis

Reported in Eastern Australian prawns (particularly QLD), currently considered exotic to NSW.

Associated with monodon broodstock mortality

Associated with mid-crop mortality syndrome

Associated with reduced larval survival from positive broodstock


Mourilyan Virus- appears non pathogenic

Mourilyan virus has been isolated in P.Monodon populations Horizontal transmission reported Observed in muscle, gill, HP, lymphoid and

haematopoietic and neural tissue Diagnosed by EM, PCR and Histopathology Uncertain if it is pathogenic to monodon at all In co-infections with GAV, it is GAV that appears to

be the cause of mortality, not MoV


White tail disease (Macrobrachium rosenbergii

Nodavirus) Abdomen is milky and opaque-

discolouration starts at the tail and eventually spreads throughout the body

High mortality rates of >95%

Outbreaks will normally occur in juveniles, PLs, and larvae

Present in inland Qld- risks to marine prawns


Risk Pathways

Importation of live stock- broodstock /untested PL’s

Source water/ ballast shipping increase/ ports expansion

Imported frozen uncooked product/ rec fishing bait/ processors

Importation of unpasteurised feed/ equipment

People movement

Entry of carrier crustaceans- eg soft shell frozen crab


Border Biosecurity Model

Pre-Border

• Exporting countries testing and reporting• Competent authority- are they competent to certify

freedom?• Import risk assessment

Border

• Border security- AQIS- Quarantine and testing

Post-

Border

• Surveillance/ reporting of disease on-farm• Diagnostic laboratory confirmation• State/National Emergency response protocols

Reportable Diseases in Australia

Taura Syndrome White Spot Disease Yellowhead disease- Yellowhead virus Gill-associated virus Infectious Hypodermal and Haematopoietic Necrosis Crayfish Plague (Aphanomyces Astaci) White tail disease Infectious Myonecrosis Monodon Slow Growth Syndrome Milk haemolymph disease of spiny lobster Necrotising hepatopancreatitis

Documents

Australia’s Disease Status and Risk Pathways Dr Matt Landos 1 BVSc(HonsI)MANZCVS Dr Christine Huynh BVSc Future Fisheries Veterinary Service Pty Ltd