Background: Anopheles stephensi is an important urban malaria vector in the Indian subcontinent. Extensive application of insecticides evokes microevolution, which results in resistance that can be traced back to their genotypes. In this study, resistant and susceptible strains of An. stephensi for alphamethrin were selected by selective inbreeding for 27 and ten generations respectively. The biochemical basis of resistance in all the life stages was investigated. Quantitative assays were performed for proteins (total and soluble), esterases (α, β and acetylcholine) and phosphatases (acid and alkaline) by spectrophotometry, and qualitative assays for the enzymes by native polyacrylamide gel electrophoresis.
Results: The enzyme quantities significantly varied in all life stages of the resistant strain as compared with the susceptible ones. Qualitative studies showed seven isoforms for α- and β-esterases, three each for acetylcholinesterase and alkaline phosphatase and two for acid phosphatase. Exclusive bands were found in the resistant strain, such as α-Est 1 and β-Est 1 in eggs and larvae, β-Est 3 in adult males, β-Est 2 in adult females and AlkP 1, AlkP 2 and AlkP 3 in adult females, larvae and adult males respectively.
Conclusion: Variations in the quantity and specific enzyme isoforms play a key role in the development of alphamethrin resistance in An. stephensi. © 2015 Society of Chemical Industry.
Keywords: Anopheles stephensi; alphamethrin resistance; esterases; phosphatases; polyacrylamide gel electrophoresis; spectrophotometry.
© 2015 Society of Chemical Industry.