The histopathological effects of a levamisole-adjuvanted Vibrio anguillarum vaccine on Atlantic salmon (Salmo salar L.)

Atlantic salmon (Salmo salar L.) were administered a levamisole-adjuvanted or non-adjuvanted Vibrio anguillarum vaccine by either bath or intraperitoneal (IP) injection. The potential side effects of vaccination were investigated at a histological level, with the skin, gills, anterior kidney and spleen all examined. At a gross level, no pathological changes were evident in any organs. Observations of histological structures found that the skin, anterior kidney and spleen were not affected by vaccination. However pathological changes were observed in the gills of fish treated with the adjuvanted vaccine by both routes of administration. Pathology of the gills was multifocal and included hyperplasia of mucous cells, lamellar oedema, proliferation of chloride cells, inflammation and necrosis. Hyperplasia and hypertrophy of epithelial cells resulted in lamellar fusion. The abundance of lamellar associated mucous cells significantly increased in the gills of fish from groups administered the levanmisole-adjuvanted vaccine (IP and bath) (P < 0.05). However, the effect of the treatments on lamellar fusion was not significant (P > 0.05). © 2001 Elsevier Science B.V.