2nd Place: V410L kdr mutations in Aedes aegypti populations from Harris County, TX, USA, and their influence in survivorship after exposure to Permanone 31-66 in field cage tests

The primary mechanism known to confer resistance to pyrethroids in Ae. aegypti is knockdown resistance (kdr) caused by single-point, non‑synonymous mutations in the voltage‑gated sodium channel (VGSC) which alter the binding site for the insecticide. Three of the most common kdr mutations in pyrethroid‑resistant Ae. aegypti populations in the United States are V410L, V1016I, and F1534C. Previously, we analyzed females of Ae. aegypti from Harris County, TX, for the V1016I and F1534C kdr genotypes and determined with logistic regression modeling that these genotypes did not significantly increase the probability of survivorship to Permanone (pyrethroid permethrin 31% + 66% piperonyl butoxide; PBO) in field tests conducted by Harris County Public Health. Here, we examined the same females for their genotype at the V410L position in the VGSC, and for its effect on mosquito survival when genotypes at the other two kdr sites were included in the analyses. We report the first detection of the V410L mutation in Texas, and the triple homozygous resistant mutant genotype (LL/II/CC) as the most prevalent among the 716 females analyzed. Analyses of the probability of survival considering the most frequent tri-locus kdr genotypes found significant differences among operational areas, and a significant interaction of distance x genotype. Our results indicate that kdr-based pyrethroid resistance in the Ae. aegypti population of Harris County is highly frequent, highlighting the need for additional studies to assess the impact of kdr and other resistance mechanisms to aid insecticide-based control strategies.