Viral Diseases of Aquaculture Species

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Viral Diseases of Aquaculture Species
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What is a virus?

• Does not carry out independent metabolic
  functions
• Can only be seen with an electron microscope
• Carries viral genetic material DNA/RNA

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What is a virus?

• Redirects metabolic machinery of host cell to
  produce more viral DNA/RNA and viral components
• Viruses are Obligate intracellular parasites

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How do you control viruses?

• Difficult to treat
• Vaccinate using dead or attenuated viruses to
  illicit immune response
• Avoid carrier brood stock
• Avoid stress

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Channel Catfish Virus DiseaseCCVD

• Type of herpesvirus
• Primarily affects fish under 6 inches
• Sporadic in occurrence but can kill 90 percent
  of stock
• Host specific to channel catfish
• Most common June-Sept.
• Most severe in water 85 degrees F

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CCVD Clinical Signs

• Fish feed poorly
• Fish swim erratically
• Float head up in water
• Dropsy and exopthalmia
• Petechial hemorrhages at base of fins
• Pale liver, enlarged spleen

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CCVD Transmission

• Vertical through gametes
• Through water once epizootic has started
• Effluent, birds, equipment, etc.

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CCVD Diagnosis

• Suspect ccv when large s of fry or fingerlings
  begin dying above 70 deg. F
• Official diagnosis and identification requires
  special high tech lab tests

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Controlling CCVD

• No Cure
• Try to avoid carrier brood stock
• No vaccine available
• Avoid stress and use BMPs
• May use medicated feed to reduce secondary
  bacterial infections

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Salmonid viruses

• IPNV - Infectious Pancreatic Necrosis Virus
• affects small salmonids gt6, especially brook
  trout
• VHS - Viral Hemorrhagic Septicemia
• primarily rainbow trout _at_ 59-66 deg F

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What happens if these occur?

• Fish generally destroyed to prevent spread
• Sanitize facility

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Lymphosystis Virus Disease

• Most common disease of fish
• Occurs in marine, freshwater and ornamental fish
• Lesions occur primarily in connective tissue of
  fins and skin.
• Lesions are hypertrophied cells that can enlarge
  up to 1000x normal size
• No cure, but usually not fatal

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Taura Syndrome (TSV)

• first recognized in shrimp farms in Ecuador in
  1992 where the disease caused catastrophic losses
  
• spread rapidly to virtually all of the shrimp
  growing regions of the Americas through shipments
  of infected post-larvae and brood-stocks
• reddening of the tail fan and visible necrosis in
  the cuticle
• has been demonstrated to remain infectious in the
  feces of sea gulls that have ingested infected
  shrimp.

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• What is it?
• Try to find out why it is
• What species it affects
• Economic results of this new disease