The immune response of Atlantic salmon, Salmo salar L., to the causative agent of bacterial kidney disease, Renibacterium salmoninarum

Both under‐yearling and post‐yearling Atlantic salmon parr produced high agglutinating antibody titres in response to a single intraperitoneal injection of killed bacterial kidney disease (BKD) cells emulsified in. Freund's complete adjuvant (FCA), Low or no response was observed in animals injected with BKD cells in saline or in animals vaccinated by hyperosmotic immersion. Immunological duration was insufficient in fish vaccinated as under‐yearling parr to provide protective immunity 2 years later when the fish had become smolts. Atlantic salmon post‐yearling parr injected with BKD cells in FCA demonstrated a reduced prevalence of BKD lesions compared to control animals when both were observed as smolts 1 year after vaccination.