Biochemical effects of lambdacyhalothrin on activities of some detoxifying enzymes of Anopheles gambiae life cycle stages

Abstract

Recent decrease in global malaria burden was achieved through vector control interventions with pyrethroid insecticides. This study was carried out to determine the influence of lambdacyhalothrin on the physiology and activities of some detoxifying enzymes and to establish the systemic effects on Anopheles gambiae. The life cycle stages of the vector were exposed to six different concentrations of lambdacyhalothrin, in an insectary. After the toxicity tests, 325 each, of the dead eggs, larvae and pupae, and 175 of the dead adults from the toxicity test, were carefully selected and further used for enzyme study. Fifty (50) individuals were used for experimental study and 25 as control, for each of egg, larvae and pupae; 25 were used for experimental study and 25 as control for the adult. Each sample was homogenized in 10ml 0.1M phosphate buffer of pH 7.4, filtered and the filtrate used for enzymes study. Determination of the enzymes: aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) was done using standard biochemical methods. The results showed that 97% mortality of the life cycle stages was achieved following exposure to six concentrations of lambdacyhalothrin. Some concentrations (1 and 05µg/l) induced stimulatory effect on the enzyme activities while others (15 and 25µg/l) elicited inhibitory effect and some (10µg/l and 20µg/l) had no significant effect (p>0.05) on the enzyme activities. Alkaline phosphatase (ALP) was the most active in all the life cycle stages. Nevertheless, in older stages (pupae and adults), AST and ALT activities were significantly (p<0.05) elevated. This suggests that lambdacyhalothrin is promising in providing effective mosquito control. The results also suggest that the enzymes play a part in detoxification of lambdacyhalothrin and hence could be correlated with the pyrethroid tolerance status of A. gambiae.