Bacterial Kidney Disease (BKD) in Salmonids – Gross Pathology

Atlantic salmon (adult-1500 g) with BKD. Note the multiple granulomas in kidney. These severe lesions lead to renal failure

Bacterial kidney disease (BKD) is a chronic systemic infection of salmonid fish, the cause of which is the gram-positive diplobacillus, Renibacterium salmoninarum. Although BKD is most common in salmonids, both farmed and wild, R. salmoninarum is also found in other fish species, such as cyprinids and sablefish Anoplopoma fimbria. R. salmoninarum grows intracellularly in the phagocytic cells of the fish, resulting therefore in a largely granulomatous host response, although the early response to infection does involve significant numbers of neutrophils. Clinical signs and external lesions...

Spawning Rash – Gross Pathology

Rainbow trout, multi-focal granulomatous dermatitis

The bacterium Renibacterium salmoninarum is a small (~ 1.0 μm), intracellular, non-motile diplobacillus, gram +, that is slow growing and a fastidious pathogen. The external gross findings on the skin could be a good example of chronic-active dermal o subdermal lesion associated with R. salmoninarum. “Spawning rash” can be observed in adults, particularly at or around spawning time. Lesions may be largely dermal, often centering round scale-pockets to produce multifocal chronic-active dermatitis. Alternatively the response, mainly in the superficial muscle, may be so severe as...