Impact of voltage-gated sodium channel kdr mutations (V1016I, F1534C) on survivorship of Aedes aegypti (L.) mosquitoes from Harris County (Texas, USA) after exposure to Permanone® in field cage tests

Emerging arboviruses such as Zika, dengue, yellow fever, and chikungunya are a growing public health concern in areas with Aedes aegypti populations. The primary strategy in reducing their adult populations and quell potential disease outbreaks relies on insecticide-based control with pyrethroids, which is threatened by the development of insecticide resistance. A major mechanism of pyrethroid resistance in mosquitoes is target site insensitivity from knockdown resistance (kdr) mutations in the voltage-gated sodium channel. Frequent application of ULV pyrethroid by Harris County Public Health in Houston (Texas) and peripheral cities targeting Culex quinquefasciatus populations may have selected for resistance in local Aedes aegypti mosquitoes. To assess the influence of pyrethroid resistance on vector control, females of Ae. aegypti collected from eight mosquito control operational areas in Harris County, were treated in field cage tests with the pyrethroid Permanone® 31-66 at different distances. The females were then genotyped for two kdr mutations associated with pyrethroid resistance (V1016I and F1534C) by melting curve analyses. Survivorship of females collected from the operational areas was higher than the pyrethroid-susceptible Orlando strain females and increased with distance from the treatment source. Pyrethroid-resistant homozygous genotypes were broadly distributed throughout Harris County at high frequency. The impact of resistant genotypes on survivorship of females will be further discussed under the context of current control methods. The presence of a pyrethroid-resistant Ae. aegypti population may jeopardize vector control efforts in Harris County. This is the first report of kdr genotypes of Aedes aegypti in Texas.