Pathogenesis of infectious pancreatic necrosis virus infection in brook trout, Salvelinus fontinalis (Mitchill), following intraperitoneal injection

Abstract. The pathogenesis of IPNV infection was examined in young brook trout following intraperitoneal inoculation. Fish were sampled sequentially and the distribution of virus determined by virus isolation, histopathology and immunofluorescence. Following intraperitoneal inoculation, virus entered the peritoneal cavity and by 2 days post-inoculation virus had interacted with the pancreatic exocrine cells. Replication in these cells resulted in the production of IPNV-specific antigen, necrosis of infected cells, and spread of infectious virus to adjacent tissue. Areas of viral replication were at first multifocal but tended to merge as they grew. Eventually, most of the acinar tissue became involved and only small pockets of normal acinar cells remained. Twelve-week old brook trout survived with only a small amount of functional exocrine pancreas and limited virus replication continued in this tissue for weeks. Extensive virus replication appeared to take place only in the pancreas although viral antigen and slight pathological changes were found in the renal interstitium and livers of some fish.