抄録
The influence of inoculative quantity of infectious pancreatic necrosis virus (IPNV) on mor-tality of rainbow trout fry Salmo gairdneri was studied. IPNV-Buhl strain which is the most dominant IPNV-strain in Japan was used for a challenge virus and a highly sensitive strain to IPNV (RT-101 strain, 0.13 g and 0.26g in the mean B. W.) was employed as an experimental fish in this study. The fry was immersed with 105.0, 104.0, 103.0, 102.0 and 101.0 TCID50/ml of IPNV at 15°C for 1h and incubated at 15°C for 28 days. As the results obtained, cumulative mortality in the fry weighing 0.13g was 92, 84, 80, 51 and 26% and in the fry weighing 0.26g was 61, 38, 26, 0 and 0%at 105.0, 104.0, 103.0, 102.0 and 101.0 TCID50/ml of IPNV, respectively. At 105.0 TCID50/mlof IPNV, the peak of daily mortality was on the 4-6th day after inoculation and the mortalitypattern was a typical acute type. The daily mortality became lower, the peak of the daily mortalitywas delayed and the death of fry continued until later, as tine inoculative quantity of IPNV wasreduced.
