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...

Nephrocalcinosis in Fish – Gross pathology

Figure 1. Gross appearance of nephrocalcinosis. The kidney is swollen and grey with an irregular surface and white mineral deposits in the ureters.

Nephrocalcinosis (or urolithiasis) in fish is a chronic inflammatory condition of unknown aetiology in which calcium and other minerals precipitate as hydroxyapatite within the distal renal tubules and collecting ducts. The disease usually records low mortality and although food conversion efficiency is probably impaired, the major concern about the condition centres round a reduction in carcase quality at slaughter. In severe cases, the muscle dorsal to the kidney may also be affected. There are some predisposing factors for this condition like high levels of carbon...