Resistance profiles of major mosquito disease vectors in Maricopa County, Arizona

Resistance to insecticides is a growing global issue in mosquito populations. It is caused by selective pressures from increasing overuse and untargeted use of pesticides to control mosquitoes and other agricultural or household pests. The Dengue vector Aedes aegypti (AAEG) in metropolitan Phoenix, AZ, has been shown to have high levels of target-site resistance mutations at the 410, 1016, and 1534 loci of the kdr gene. However, the status of insecticide resistance in Culex spp. in the Valley is largely unknown, a rather concerning issue due to the genus’s role as the West Nile Virus vector. Insecticide resistance in both AAEG and Culex spp. are thought to be controlled by both metabolic enzyme pathways and target-site resistance pathways. Here, we will present our ongoing work to determine the intensity of pyrethroid resistance in both AAEG and Cx. quinquefasciatus in the highly populated urban areas of the Maricopa County, AZ. Phenotypic resistance is determined by establishing dose-response curves using topical application bioassays. Mosquitoes are further genotyped using melt-curve analysis for common kdr target-site mutations, and metabolic resistance is assessed using colorimetric enzyme activity assays. This data will allow us to compare the intensity of resistance between both common vector species; which resistance mechanism dominates, if any; and to predict possible outcomes of programmatic fogging on the reduction of disease risk.