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ARS Home » Southeast Area » Auburn, Alabama » Aquatic Animal Health Research » Research » Publications at this Location » Publication #218869
Title: Continuous exposure to infectious pancreatic necrosis virus during early life stages of rainbow trout, Oncorhynchus mykiss(Walbaum)

Author
item Bebak, Julie
item MCALLISTER, PHILIP - USGS NAT'L FISH HLTH LAB

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2008
Publication Date: 3/1/2009
Citation: Bebak, J.A., Mcallister, P. 2009. Continuous exposure to infectious pancreatic necrosis virus during early life stages of rainbow trout, Oncorhynchus mykiss (Walbaum). Journal of Fish Diseases. 32:173-181.

Interpretive Summary: During an epidemic occurring in the aquatic environment, relatively greater pathogen concentrations may be expected near a wild, schooling fish population or at the discharge or periphery of a fish culture system. As the pathogen is dispersed, concentrations will be diluted to relatively lower levels. Consequently, both wild and farm-raised fish populations may be chronically exposed to low concentrations of water-borne pathogens. Rainbow trout (Oncorhynchus mykiss, Walbaum) were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 10, 1,000, or 100,000 pfu/L of water to estimate the effects of chronic IPNV exposure on early life stages. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu/L exposure did not occur until IPNV concentration was 100,000 pfu/L at low density and 1,000 pfu IPNV/L at high density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur when ambient concentrations of virus are less than 1,000 pfu IPNV/L. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, inputs of virus concentrations greater than 10 pfu/L would likely result in IPN epidemics in the aquaculture facility.

Technical Abstract: Rainbow trout (Oncorhynchus mykiss, Walbaum) were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 10, 1,000, or 100,000 pfu/L of water to estimate the effects of chronic IPNV exposure on early life stages. Fish density averaged 35 fish/L or 140 fish/L, with a tank flow rate of 250 mL/min Virus exposure began at 6 d before hatch and continued until fish were 44 d old. Discrete-time event analysis was used to explore the patterns of survival and mortality. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu/L exposure did not occur until IPNV concentration was 100,000 pfu/L at low density and 1,000 pfu IPNV/L at high density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur occur when ambient concentrations of virus are less than 1,000 pfu IPNV/L. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, inputs of virus concentrations greater than 10 pfu/L would likely result in IPN epidemics in the aquaculture facility.