Vaccination against Furunculosis in Arctic Char: Efficacy of a Commercial Vaccine.

Arctic char Salvelinus alpinus are susceptible to furunculosis, a serious bacterial disease that affects the productivity of salmonid farms around the world. The objective of this laboratory study was to evaluate the efficacy of a commercially available vaccine against furunculosis in two strains of Arctic char. Labrador and Nauyuk char were injected with Aqua Health Furogen 2 or 0.9% NaCl. At 87 and 108 d postvaccination, fish were challenged with Aeromonas salmonicida by immersion. In both challenges, the Aqua Health vaccine provided significant protection against furunculosis; percent cumulative mortality was significantly (P = 0.005) greater for the fish vaccinated with 0.9% NaCl than for those vaccinated with Furogen 2. Strain (P = 0.30), days since vaccination (P = 0.38), and the interaction between vaccine and strain (P = 0.40) were not significant. The point estimate for the preventive fraction (PF) was greater than 0.90 for the Labrador fish vaccinated with Furogen 2; for the Nauyuk fish, the PF was 0.89 and 0.38 at 87 and 108 d, respectively. Relative proportion survival values were also estimated and were usually similar to, but always lower than, the PF estimates.