Infectious pancreatic necrosis (IPN) virus carriers and antibody production in a population of rainbow trout (Salmo gairdneri).

A total of three hundred and fifty-seven 2-year-old rainbow trout from a hatchery were examined for IPN virus over a period of 5 months. The overall virus isolation rate was 23.2%. The kidneys yielded virus most frequently while the spleen and pancreas-caeca yielded virus less frequently, and the gonads and feces yielded virus infrequently. During this period there was a decline in carrier rate as well as a decline in the numbers of infectious virions in the organs. These decreases were accompanied by elevated levels of neutralizing antibody in the sera. Fish with higher antibody levels were found to lose their IPN carrier status more frequently than those with lower antibody levels.