Viral Diseases of Aquaculture Species

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

What is a virus? Redirects metabolic machinery of host cell to produce more viral DNA/RNA and viral components Viruses are Obligate intracellular parasites

How do you control viruses? Difficult to treat Vaccinate using dead or attenuated viruses to illicit immune response Avoid carrier brood stock Avoid stress

Channel Catfish Virus Disease CCVD 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

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

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

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

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

Salmonid viruses IPNV - Infectious Pancreatic Necrosis Virus affects small salmonids >6”, especially brook trout VHS - Viral Hemorrhagic Septicemia primarily rainbow trout @ 59-66 deg F

What happens if these occur? Fish generally destroyed to prevent spread Sanitize facility

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

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.

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