Frequency of Detection and Survival of Infectious Pancreatic Necrosis Virus in a Carrier Population of Brook Trout (Salvelinus fontinalis) in a Lake

Abstract

Brook trout (Salvelinus fontinalis) distributed from a hatchery into a small enclosed lake were examined for IPN virus carriers over a period of 21/2 yr. The carrier rate of 90% at the time of distribution decreased to 69%, but organ analysis showed differing trends in carrier rate. There was a decrease of virus in the pancreas–caeca (82–32%) and an increase in the feces (2–39%) whereas virus was detected to be present at a constant level in the kidneys (53–57%) and the spleen (8–14%). Virus was not detected in the gonads except for a few which yielded virus later in the sampling period.These data indicate that brook trout IPN carriers distributed from a hatchery into lakes do not readily lose their virus over a period of several years, and that both caeca and kidneys are organs of choice for the detection of virus.Neutralizing antibody levels were very low or nondetectable in the carrier population and could not be correlated with yield of virus.