Abstract

During 1992 a fatal disease condition occurred in six rainbow trout farms in Scotland and northern England. Clinical signs included exophthalmia, swollen abdomen, pale gills, darkening of the skin, skin lesions, enlargement of the spleen and ascites in the peritoneal cavity. Cytophaga psychrophila (=Flexibacter psychrophilus) was isolated from internal organs and skin lesions of affected fish. Bacterial isolates showed serological cross-reactivity with C. psychrophila NCMB 1947.