THE RELEVANCE OF INFECTIOUS PANCREATIC NECROSIS VIRUS (IPNV) IN FARMED NORWEGIAN TURBOT (SCOPHTHALMUS-MAXIMUS)

In 1989, during a period when high mortalities of turbot fry were reco rded in several commercial farms, samples for virus detections were co llected in 6 farms. Samples were also collected from two broodstock po pulations and egg batches from one farm, and from wild fauna in the su rroundings of a second farm where infectious pancreatic necrosis virus (IPNV) was isolated from turbot fry with pronounced necrosis in exocr ine pancreatic tissue. IPNV was isolated from fry collected in 3 of th e farms, from invertebrate fauna and in a few samples from wild fish. Virus was not detected in broodstock or egg batches. Immunohistochemic al examination of affected fry revealed severe pancreas necrosis, and a moderate-to-strong, IPNV-specific reaction in the cytoplasm of degen erated exocrine pancreatic cells. This ''amination indicates that IPNV might cause infectious pancreatic necrosis in turbot fry. After an IP NV bath challenge of turbot fry, IPNV was recovered from viscera of th e fry. This transmission of virus indicates that IPNV might infect tur bot fry. An increased mortality was recorded in challenged fry, but hi stological and immunohistochemical examination of moribund and survivi ng specimens did not reveal any clear pathological changes. The findin g of IPNV in wild fish, invertebrate fauna and in Artemia point to sev eral potential virus-sources and ways of transmission.