Mycotic involvement in epizootic ulcerative syndrome of freshwater fishes of bangladesh: a histopathological study

摘要

Five species of freshwater fishes (Cirrhinus mrigala, Catla catla, Puntius sophore, Glossogobius giuris and Labeo rohita) were affected by the epizootic ulcerative syndrome (EUS) in the Bangladesh Agricultural University campus. A monthly sampling was carried out from October 1997 to March 1998. Clinically and histologically C. mrigala was severely affected by EUS, followed by C. cotlo, P. sophore and G. giuris. L. rohita was the least affected species. Large, deep and whitish ulcers were recorded in the lateral region (near the dorsal fin) and caudal region where parts of fins, scales and muscle were lost in most of the EUS affected fish. Massive necrosis of the epithelium and muscle tissue was observed in the affected tissue surrounding the granuloma. The granuloma due to fungal infection consisted of mononuclear epithelloid cells and fibrillar structures. Fungal granulomas were also found in the liver of C. mrigala and C. cotlo and in the kidney of C. mrigala only. However, the liver and kidney of other species had necrotic hepatocytes, renal tubules and glomeruli associated with many inflammatory cells. Water temperature, alkalinity and hardness were reduced in the months of December, January and February in comparison with other months. Clinically and histologically, in the colder months (December, January and February), all fish specimens were more affected by EUS in comparison with other months. The clinical signs, infection mode and histopathology of the disease observed in the present study resemble mycotic granulomatosis. Thus, the consistent involvement of fungus and its similarity in pathology to EUS in other countries, indicate that fungus is one of the pathological agents of EUS.