Field and laboratory detection of the altered acetylcholinesterase resistance genes which confer organophosphate and carbamate resistance in mosquitoes (Diptera: Culicidae)

Abstract

A simple field method for direct detection of an altered acetylcholinesterase (AChE)-type organophosphate and carbamate resistance mechanism in individual insects was developed. The test will allow accurate differentiation by eye, on the basis of a colour change, of homozygous-susceptible and heterozygous or homozygous-resistant individuals. In initial field trials of this test in Sri Lanka, Anopheles nigerrimus Giles and Culex tritaeniorhynchus Giles were shown to contain this type of resistance gene, while a further nine species of mosquito had no evidence of it. Frequencies of the altered AChE gene in A. nigerrimus were estimated to be higher than those of C. tritaeniorhynchus, where the gene was found in only one of three localities in the island. The implication of the increase in prevalence of the AChE resistance gene in mosquito populations is discussed.