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Adult Control and Insect Resistance Challenges

Adult Control and Insect Resistance Challenges

100 - Exploring Pyrethroid Resistance Mechanisms in Aedes aegypti and Culex quinquefasciatus in Arizona: A Focus on Target-Site and Metabolic Resistance

Wednesday, March 5, 2025
9:10 AM – 9:20 AM AST
Location: 208 B
Abstract: Resistance to insecticides is a growing global issue in mosquito populations. Culex quinquefasciatus is the main the vector of West Nile virus in Maricopa County, Arizona, having caused 1,487 cases of the viral disease and 101 deaths in the county in 2021. Aedes aegypti, the Yellow Fever and Dengue vector, was found to have transmitted the first locally-acquired case of Dengue in Maricopa County in 2022. Combating these vectors with chemical intervention has been difficult due to various resistance mechanisms known to convey phenotypic resistance in mosquitoes, in particular mutations at the insecticide target site and increased expression of detoxification enzymes which break down insecticides. Currently, the status of insecticide resistance in Cx. quinquesfaciatus is largely unknown. Here, we will present our ongoing work on determining the phenotypic, genotypic, and enzymatic levels of resistance in Cx. quinquefasciatus and Ae. aegypti. We established deltamethrin dose-response curves for both Ae. aegypti and Cx. quinquefasciatus populations at 6 different sampling sites in Maricopa County using the topical application bioassay. Further, we assessed the prevalence of knockdown resistance (kdr) mutations at the 1014 locus of the vgsc gene in Cx. quinquefasciatus and at both the 410 and 1016 loci in Ae. aegypti. Lastly, we quantified the detoxifying enzyme activity of 4 different enzymes from the Cx. quinquefasciatus field collections. Overall, our data demonstrate a high level of pyrethroid resistance in both species (Resistance Ratio RangeAedes = 287-1300, Resistance Ratio RangeCulex = 46-81) with both target-site and metabolic resistance mechanisms highly prevalent. We will discuss the relative impact of both of these resistance mechanisms on phenotypic resistance outcomes in both disease vectors.