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The article focuses on atypical aeromonas salmonicida infection in Atlantic cod, gadus morhua L. In this study skin lesions, kidney and intestine were cultured on tryptic soy agar (Difco) with and without NaCI supplement to 2 %, as well as on blood agar. Thirty freshly caught cod from Terence Bay were sampled for bacteriology in an attempt to establish the source of the infection. The cod injected with A. saimonicida and sampled bacteriologically after death yielded A. salmonicida from all sites except the intestine, which gave a heavy growth of vibrio anguillarum.

The histopathology of an atypical Aeromonas salmonicida found in Atlantic cod, Gadus morhua L., is described. Unlike members of the Salmonidae, the cod showed a well-developed host reaction to A. salmonicida involving encystment of the bacteria. When Atlantic salmon, Salmo salar L., were given an intra-muscular injection with suspensions of cultures of this strain of A. salmonicida no cellular host reaction was observed. When cod were given a similar injection the bacteria showed degenerative changes, leucocytes accumulated, and cyst formation was seen in the spleen and kidney. Since cod can be infected by this organism the possibility exists that they could act as carriers, a source of infection for salmonids in saltwater cage culture or in the wild. [ABSTRACT FROM AUTHOR]

Heavy mortalities of underyearling Atlantic salmon parr have occurred at the Mactaquac Fish Culture Station in New Brunswick as the result of `saddle-back' disease. The organism causing this lesion was isolated and identified as Flexibacter columnaris. This bacterium was transmitted to other salmon parr, where it produced the typical saddle lesion from which it was re-isolated. The condition was more readily transmitted at 20°C than at 15°C. Transmission required entrance to the dermis through a break in the epidermal surface and was unsuccessful in intact fish. The morphology of the saddleback isolate and its histopathological effect on the fish tissues is described. F. columnaris appeared to be restricted to the dermis and underlying muscle of the saddle area when histological techniques were used, although it was also isolated from the kidneys of some affected fish. The gills, kidney and other organs of the fish did not seem to be affected by the presence of F. columnaris. [ABSTRACT FROM AUTHOR]

Competing Interests: Statement of Conflicting Interest:The authors declare no conflicts of interest.