Pathology of Atlantic salmon Salmo salar intraperitoneally immunized with oil-adjuvanted vaccine. A case report

Abstract

Gross and histopathological lesions in farmed Atlantic salmon Salmo salar L. immunized by intraperitoneal injections of oil-adjuvanted vaccines are reported. A few fish farms report serious side effects leading to poor feed uptake and conversion, retarded growth and downgrading at slaughtering due to severe adhesions between abdominal organs and body wall. The lesions consist of granulomatous tissue adhering to and embedding different visceral organs in such a way that normal functions may become severely affected. Histologically, the tissue is characterized by granulomas embedded in a fibrous granulation tissue with high numbers of eosinophilic granule cells. Possible explanations for the occurrence of severe lesions at some farms are discussed.