Experimental pancreas disease in Atlantic salmon Salmo salar post-smolts induced by salmon pancreas disease virus (SPDV)

Abstract

Disease-free Atlantic salmon Salmo salar post-smolts (mean weight 87 g) were maintained in a flow-through ozone-sterilized sea water system at 12 to 15°C and ambient salinity. One hundred fish were intraperitoneally inoculated with 0.1 ml of salmon pancreas disease virus (SPDV) of a titre 107 TCID50 ml-1. Fifty fin-clipped uninoculated smolts were placed in- contact in the same tank. One hundred fish were kept in another tank as controls and were inoculated with a lysate from un-infected Chinook salmon embryo (CHSE-214) cell cultures. Blood and tissues for virus isolation, serum neutralisalion tests and histological examination were taken at intervals up to 42 days post inoculation (dpi). Virus was re-isolated from SPDV inoculated smolts at 7, 10, 15 and 21 dpi and in-contact fish at 14 and 21 dpi. Neutralising antibody was first detected in the inoculated fish at 10 dpi and in the in-contact fish 11 d later. Clinical signs and microscopic lesions indistinguishable from naturally occurring pancreas disease (PD) were observed in SPDV inoculated and in-contact smolts. No lesions were detected in the negative controls. These results provide strong evidence that SPDV is the etiologic agent of PD in farmed Atlantic salmon in Ireland.