Health status of eels from open waters: a clinical and histopathological approach


An experiment was conducted to know the health and disease problems of two freshwater eels, viz. Monopterus cuchia and Mastacembelus armatus which were collected from open waters of Mymensingh region (i.e. Kailla beel and Brahmaputra river) through clinical and histopathological examination. Water quality parameters, clinical and histopathological examinations were carried out on a monthly basis. The average value of temperature and dissolved oxygen (DO) decrease in winter season. During month of December and January, eels were found to be severely affected and characterized by clinical signs of red spots, rough skin and deep ulcers in the ventral and lateral regions of the body. Additionally, there weresevere necrosis in the skin and muscle of eels, presence of melanomacrophage, loss of epidermis, vacuoles, split of dermis and muscle were observed. Histopathological examination of gills were revealed missing of primary and secondary gill lamellae, necrosis, hyperplasia, highly hypertrophied and hemorrhagic gill lamellae. In liver, pyknotic and hyperplasid hepatocytes, necrosis, hemorrhages and vacuoles were evident. Hemorrhages, vacuolation, necrosis, missing and ruptured kidney tubules, pyknosis and presence of fungal granuloma were the major pathological alterations of kidney. The observed signs of diseases in eels could be realted to epizootic ulcerative syndrome (EUS), dactylogyrosis, parasitic and bacterial diseases associated with other opportunistic pathogens.. Our results indicated that the examined eels of Kailla beel river were found to be more severely affected than eels of the Brahmaputra oneduring the colder months of the year (December and January), in comparison to other months of the year.

Key words: Eel fish, Health and disease, Open water, Histopathology, EUS