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...

Proliferative Kidney Disease in Salmonids (PKD) – Gross Pathology

Rainbow trout with PKD. There is a marked hyperplasia of interstitium with the kidney thrown into bulbous ridges. The reddening is tge result of secondary yersinia infection.

Proliferative kidney disease (PKD) is an endoparasitic disease of salmonid fish caused by Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea).  This chronic, largely renal interstitial disease is caused by the extraporogonic but intracellular stages of the parasite, which cause a severe granulomatous host response. The severity of the disease is linked to water temperature, with roughly 15 degrees °C as the cut-off: below that temperature, lesions and clinical disease are minimal. Above that temperature, however, lesions can be severe and mortality high. Inevitably, global warming has resulted in...