Epizootiology of Renibacterium salmoninarum, the causal agent of bacterial kidney disease in salmonid fish.
R. salmoninarum was recovered from rainbow trout with a selective medium. In asymptomatic fish, small numbers of Renibacterium colonies were recovered only from the anterior part of the kidney; in clinically diseased fish, dense pure culture growth was obtained from kidney, spleen, heart, blood, ascitic fluid and faeces. R. salmoninarum was not recovered from the water or sediment of 56 infected or uninfected freshwater fish farms in England and Wales. Laboratory experiments showed that the pathogen was excreted in the faeces of clinically diseased fish and that bacterial cells survived for up to 21 days in sediment/faecal material.