Reduction ofRenibacterium salmoninarumculture activity in Atlantic salmon following vaccination with avirulent strains

A series of challenge experiments were conducted to determine the efficacy of vaccination against bacterial kidney disease (BKD) in Atlantic salmon using an avirulent mutant ofRenibacterium salmoninarum(RsTSA I), and a related Gram-positive bacterium (Rsx II). Vaccination had a pronounced effect on the presence of the pathogen in fish kidney tissue. At 14 weeks after infection, the relative percentage of fish which were culture negative forR. salmoninarumwas 69·0 and 81·2 respectively for the two strains compared to 85·8% culture positive for the unvaccinated control group. Furthermore the use of a polymerase chain reaction (PCR) test to detectR. salmoninarumbeing shed from the asymptomatic fish clearly identified the pathogen in water from tanks containing the unvaccinated group but not from water taken from the tanks vaccinated with either of the vaccine strains.