Elevated levels of enzymes activity to Deltamethrin in a laboratory selected strain of Anopheles stephensi (Liston, 1901), urban malaria vector

The current study was undertaken to investigate the effects of deltamethrin exposure on An. stephensi (originating from Pondicherry), under laboratory conditions up to 40 generations. The median elevated levels of Glutathione S-transferases, (GSTs), non-specific esterases, monooxygenases, Glucose 6 Phosphate Dehydrogenase (G6PD) and Cytochrome c oxidase were quantified every fourth generation. Three day-old unfed adult female mosquitoes were exposed to sublethal dosages of deltamethrin at 0.004%, 0.005% and 0.01% and adult survivors were evaluated up to 40 generations. The result showed that 3.56-fold increase in the overall tolerance level in the adults. The outcome of the biochemical analysis of tested population was compared with those of the unexposed population. Results revealed that the significant (P< 0.0001) increased median levels in glutathione -S-transferase, esterase activity and monooxygenase in An. stephensi when compared with unexposed mosquitoes. In addition, G6PD and cytochrome c oxidase were also measured and showed that significant (P< 0.0001) enhanced activity in eighth generation when compare to parental strain. In conclusion, it appears that the development of physiological resistance to deltamethrin selected population of An. stephensi. The analysis of different enzymes involved in the physiological activities of vector mosquitoes showed the development of metabolic resistance to deltamethrin. These measures could be used to screen the insecticide resistance status.