Efficacy of mosquito coil against field population of Aedes (Stegomyia) aegypti (Linnaeus) possessing F1534C mutation

Mosquito coil is one of the popular mosquito control tools in many African countries including Ghana. In this study, we assessed the efficacy of mosquito coil against Aedes (Stegomyia) aegypti (Linnaeus) population possessing F1534C kdr mutation. Larvae collected from three urban areas in the Central Region of Ghana were reared to adults. Standard WHO tests protocol for insecticide susceptibility and evaluation of mosquito coils were conducted using three popular brands of mosquito coils against adult females. Individual mosquitoes that either died or survived the bioassays were selected for F1534C kdr genotyping using an AS-PCR technique. At the full exposure time, we found more than 98% mortality, including individual mosquitoes with the resistant allele. However, individuals with the resistant allele were 19 times more likely to survive the coils, compared to the ones with susceptible allele, when the exposure time was decreased by 2/3 of the diagnostic time, suggesting a dose-dependent resistance phenotype. In summary, the F1534C kdr mutation did not affect the efficacy of the mosquito coils tested at the recommended diagnostic exposure time. However, worthy of note is the observed increased survival of mosquitoes carrying the 1534C kdr allele under sub-optimal exposure, suggesting that this allele may be under selection due to the development of a tolerance phenotype in Ae. aegypti population. This result is very worrying since most households use mosquito coil as spatial repellents where mosquitoes are usually exposed to sub-lethal doses of the coil, and could select for the resistant mutation in Ae. aegypti