Observations on the histological alterations in various tissues of EUS affected fish, Channa striatus (Bloch).

Histopathological investigations have been made on the skin, liver, kidney and intestine of, (EUS) affected fish, Channa striatus and following anomalies have been observed. Varying degree of degeneration has been observed in the epidermis, dermis, hypodermis and underlying musculature. In all the cases, the skin lost the scales and epidermis completely at the site of infection. The dermis along with hypodermis showed the signs of necrosis. Necrosis also took place in subcutaneous layer underlying the hypodermis. Necrotization and formation of granulomas can clearly be seen in circular and longitudinal muscle layers. The liver exhibited the loosening of tissue and distension in cell bodies. While in case of kidney, shrinkage took place in all the components. Similarly, the intestinal villi got necrotised alongwith their constituent elements.

Haematological investigations on fishes infested with fungal growth.

Considerable changes have been observed in the haematological parameters of Labeo rohita, Mystus cavasius, Nandus nandus and Puntius sarana infested with Aphanomyces sp., Saprolegnia parasitica, Achlya prolifera and Dictyuchus monosporus, respectively. Substantial decline have been observed in the number of erythrocytes and lymphocytes. The number of granulocytes and monocytes were noticed significantly increased. The amount of haemoglobin has also been decreased drastically in all the cases.

Role of bacteria in the epizootic ulcerative syndrome (EUS) of fishes.

Bacteriological examination of certain water bodies and fishes carrying EUS was carried out. As a whole, 17 species of bacteria were isolated from the investigated water bodies and EUS affected fishes. The species of bacteria isolated from fishes are common to those isolated from water. Experimental infection trials conducted suggested that Aeromonas hydrophila in association with Pseudomonas fluorescens, may be playing the role of primary aetiological agent in producing EUS in fishes.