Acute exposure to fenthion in juveniles of white cachama (Piaractus brachypomus): toxic effects, changes in cholinesterase activity and potential use in environmental monitoring

Fenthion is an organophosphate insecticide used worldwide that may pollute waters after its application causing potential problems in public health and poisoning in domestic and wildlife animals. Objective: to evaluate toxic effects, butyrylcholinesterase activity (BChE) and use in environmental monitoring, 34 juveniles of white cachama (Piaractus brachypomus) were distributed in 3 groups (control, 0,13 ppm and 2 ppm fenthion) for 96 h. Materials and methods: fish were exposed in 10-gallon tanks; symptoms, gross lesions post-mortem, viscerosomatic index (VSI) and plasma BChE activity were evaluated. Mean comparisons for each variable among treatments were performed (ANOVA, α=0,05). Results: severe signs were seen in 3 specimens (3/11) of 2 ppm fenthion between 11 and 34 h of exposure. These signs were frantic swimming, muscle tremors and loss of swimming axis. In 0,13 ppm, mild to moderate signs (tremors and caudal fin flapping) were observed in some of the fish. The VSI (control = 5,3 ± 0,5; 0,13 ppm = 6,9 ± 0,3 and 2 ppm = 7,3 ± 0,6) was significantly different between exposed to fenthion and controls. BChE activity (control = 185,0 ± 20,4; 0,13 ppm = 12,5 ± 2,3 and 2 ppm = 9,8 ± 1,8 nmoles / ml plasma / min) showed significant inhibition in exposed to fenthion as compared to controls. Conclusions: the present work confirmed the toxic effects of fenthion in white cachama juveniles. Results found in BChE activity suggest its use in environmental monitoring as a good biomarker of organophosphates waterborne exposure.