Fish Diseases and Management

5.1.6.2 Hitra disease

V. salmonicida is specifically responsible for the condition of Atlantic salmon coldwater vibriosis or Hitra disease. Clinical signs of hitra disease include disorganized swimming. Fish may however die in per acute phase without any obvious clinical signs. Common external signs are pallor of the gills, haemorrhage on the fin base, redness and swelling with occasional prolapse at the rectum and petechial hemorrhage on the ventral abdominal wall. There is hemorrhage on the swim bladder, within the abdominal fat and on the hepatic and other visceral peritoneal surfaces and a pale gray spleen.

Control of this disease is best achieved by maintenance of water quality, good husbandry and low stocking densities. Killed vaccines against V. anguillarum have been available since 1980. All vaccines contain heat stable lipopolysaccharides derived from cell walls. The administration is by injection, oral and immersion method.