Susceptibility status of Culex quinquefasciatus (Diptera: Culicidae) populations to the chemical insecticide temephos in Pernambuco, Brazil

BACKGROUNDCulex quinquefasciatus is the vector of many agents of human diseases, including Wuchereria bancrofti, the parasite that causes bancroftian filariasis, an endemic disease in Pernambuco State, Brazil. Although temephos is not currently used to control C. quinquefasciatus, the species might be under a selection process from incidental exposure to this compound. This study aimed to evaluate the susceptibility status of C. quinquefasciatus to temephos, using bioassays, and to investigate its putative resistance mechanisms through biochemical assays and screening of the G119S mutation in the acetylcholinesterase gene, which is associated with organophosphate resistance, carried out by PCR and sequencing. RESULTSThe results showed that only mosquitoes from Santa Cruz do Capibaribe (SC) had an alteration in their susceptibility status (RR=7.2-fold), while the other populations were all susceptible to the insecticide. Biochemical assays showed increased activity for all esterases in SC, as well as evidence of acetylcholinesterase insensitivity. The G119S mutation was detected in this population with a frequency of 0.11, but it was not found in the remaining populations. CONCLUSIONThese data show that mechanisms of temephos resistance have been selected in natural C. quinquefasciatus populations from Pernambuco, which could undermine future control actions. (c) 2013 Society of Chemical Industry