Kdr genotyping (V1016I, F1534C) of the Nav channel of Aedes aegypti (L.) mosquito populations in Harris County (Houston), Texas, USA, after Permanone 31–66 field tests and its influence on probability of survival

Abstract

Aedes aegypti (L.) is an important mosquito vector of emerging arboviruses such as Zika, dengue, yellow fever, and chikungunya. To quell potential disease outbreaks, its populations are controlled by applying pyrethroid insecticides, which selection pressure may lead to the development of insecticide resistance. Target site insensitivity to pyrethroids caused by non-synonymous knockdown resistance (kdr) mutations in the voltage-gated sodium (NaV) channel is a predominant mechanism of resistance in mosquitoes. To evaluate the potential impact of pyrethroid resistance on vector control, Ae. aegypti eggs were collected from eight mosquito control operational areas in Harris County, Texas, and emerged females were treated in field tests at four different distances from the pyrethroid Permanone 31–66 source. The females were genotyped by melting curve analyses to detect two kdr mutations (V1016I and F1534C) in the NaV channel. Harris County females had higher survivorship rates at each distance than the pyrethroid-susceptible Orlando strain females. Survivorship increased with distance from the pyrethroid source, with 39% of field-collected mosquitoes surviving at 7.62 m and 82.3% at 22.86 m from the treatment source. Both the V1016I and F1534C pyrethroid resistant genotypes were widely distributed and at high frequency, with 77% of the females being double homozygous resistant (II/CC), this being the first report of kdr mutations in Ae. aegypti in Harris County. Analysis of the probability of survival for each mutation site independently indicated that the CC genotype had similar probability of survival as the FC heterozygous, while the II genotype had higher survival than both the VI and VV, that did not differ. The double homozygous resistant genotype (II/CC) had the highest probability of survival. A linear model estimated probability of survival for areas and genotypes. The high frequency and widespread distribution of double-homozygote pyrethroid-resistant Ae. aegypti may jeopardize disease vector control efforts in Harris County.

Impact of the V410L kdr mutation and co-occurring genotypes at kdr sites 1016 and 1534 in the VGSC on the probability of survival of the mosquito Aedes aegypti (L.) to Permanone in Harris County, TX, USA

“…For egg field collection and rearing details, refer to Hernandez et al, 2021 [ 21 ]. Egg collection was conducted between November 2017 and August 2019, and the areas of origin of the mosquitoes and test dates were: Area 23, November 9, 2017; Area 419, September 9, 2018; Area 53, October 11, 2018; Area 73, November 6, 2018; Areas 45 and 75, July 16, 2019; Areas 601 and 806, August 6, 2019.…”

“…For field bioassays Ae . aegypti females were two-to-five-day-old either F 0 generation obtained from eggs collected from the field, or from the laboratory Orlando-strain colony [ 21 ].…”

“…The most frequent kdr mutations in Ae . aegypti in the Americas are V1016I and F1534C, which are normally associated with each other [ 18 – 21 ]. A study using a congenic strain (1534C:ROCK) of Ae .…”

“…aegypti mosquitoes have not been targeted for control, the frequent pyrethroid applications against Culex quinquefasciatus could have contributed to resistance development as both species are present in Harris County and these Ae . aegypti populations carry kdr mutations [ 21 , 37 ].…”

“…Previously, we analyzed in Aedes aegypti populations of Harris County the frequency of the two most reported kdr mutations in the Americas that had been associated with permethrin resistance, V1016I and F1534C [ 21 ]. These kdr mutations were widely distributed across Harris County, with 77% of all female mosquitoes analyzed carrying the double homozygous resistant genotype II/CC.…”