Experimental studies on the efficacy and side-effects of intraperitoneal vaccination of Atlantic salmon (Salmo salarL.) against furunculosis

Efficacy and side-effects of anti-furunculosis vaccination were studied in an experimental trial. One unadjuvanted and eight adjuvanted bacterins were administered by intraperitoneal injection to Atlantic salmon (Salmo salarL.) presmolts held in fresh water. Adjuvant systems represented were mineral oil, aluminium salts, glucan and levamisole. Protection, plasma antibodies, and side-effects were determined six weeks, three months, and six months after vaccination. After six weeks, four vaccination groups were significantly protected compared to unvaccinated fish. Only two groups, being vaccinated with a trivalent and a monovalent mineral oil adjuvanted vaccine, respectively, were protected after three and six months. Fish from these two groups were increasingly protected with time. These two groups also displayed significant intra-abdominal lesions. Plasma antibody levels measured against A-layer protein and sonicated cells ofAeromonas salmonicidadiffered greatly between groups, though all vaccinated groups mounted a significant response in at least one of the samplings. High antibody levels increasing with time were found in the two long-term protected groups. At all sampling times, a positive association between antibody levels and survival was found. In conclusion, only use of mineral oil adjuvanted vaccines induced durable protective immunity against virulent waterborne furunculosis challenge.