Cold water vibriosis, also called "Hitra" disease, is a problem in farmed salmon. It has caused heavy losses in Norway since the 1970's. The disease is caused by the bacterium Vibrio salmonicida (V. salm). Clinical signs are inappetence and erratic swimming. Pathology varies with stage of the disease process, but common external signs are pallor of the gills, haemorrhage on the fin base, redness and swelling. Internally, the fish is pale due to anaemia. V. salm is transmitted through the water from fish to fish.
Disease reprinted courtesy of OIE Diagnostic Manual for Aquatic Animal Diseases
, OIE (World Organisation for Animal Health), Paris, France.