The effect of trichlorfon on acetylcholinesterase activity and histopathology of cultivated fish Oreochromis niloticus.

Among the most extensively used compounds in aquaculture for the treatment of parasitic organisms are the organophosphates (e.g., trichlorfon). The influence of trichlorfon, applied to the treatment dose, on the acetylcholinesterase (AChE) activity and gill histopathology of the Nile tilapia (Oreochromis niloticus L.) was evaluated. Cultivated fish were exposed to a single application of 0.25 ppm of trichlorfon. The results indicated a significant decrease in the muscular AChE activity in the treated individuals. After 4, 8, and 24h of exposure to trichlorfon, several histopathological alterations on gill of O. niloticus were observed but only edema and blood congestion were presented up to 72 h. No inflammatory processes were observed after 96 h of exposure. The treatment dose of trichlorfon causes biochemical effects to the fish. An indiscriminated use of this pesticide will probably decrease the production parameters of a cultivated fish such as in growth rates and final weight.