| Summary: | In recent years increased attention has been focussed on fish vaccines and vaccination against diseases in farmed fish. In this study, efficacy and side effects of vaccination against atypical furunculosis in Atlantic cod (Gadus morhua L.) were studied in an experimental trial by using different adjuvants. The different adjuvanted vaccines were administered by intraperitoneal injection (i.p.) to Atlantic cod. The adjuvants used were CpG DNA, Aluminium hydroxide (Alhydrogel), and Freunds incomplete adjuvant (FIA). Efficacy of the vaccines and side effects were determined 12 weeks post vaccination, whereas serum antibodies were measured 15 weeks post vaccination. Vaccination of Atlantic cod against atypical furunculosis protects the fish and elicits specific antibody responses to experimental infection with atypical A. salmonicida. The atypical A. salmonicida bacterin alone resulted in very good protection (RPS=75%), and addition of adjuvant alone or in combination did not improve the protection significantly. This indicates that Atlantic cod can be protected against atypical furunculosis through non-adjuvanted vaccines. The injection of FIA alone gave non-specific protection, while the adjuvants CpG DNA and Aluminium hydroxide did not give any non-specific protection. The group, which received CPG DNA alone, had a higher mortality (57%) than the saline control group (53%). High specific antibody responses were demonstrated in all groups vaccinated with A. salmonicida bacterin. The responses were strongest in the groups, which received A. salmonicida in FIA. The study also assessed the side-effects 12 weeks vaccination. The vaccines containing FIA showed the most sever side-effects among the vaccinated group. Aluminium hydroxide showed a less degree of the intraabdominal side effects compared to FIA, but a delay in fish growth was observed.
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