Detection of Broadly Distributed Sodium Channel Alleles Characteristic of Insect Pyrethroid Resistance in West Nile Virus VectorCulex pipiensComplex Mosquitoes in the United States

Abstract

West Nile virus (WNV) has emerged as a health threat to the North American population since its initial outbreak in New York City in 1999. Culex (Culex) pipiens complex mosquitoes have been considered to play the primary role in the enzootic maintenance and transmission of WNV in North America. The voltage-gated sodium channel (NaCh) gene contains pyrethroid resistance-associated mutations in the coding region in many insect species. However, the knowledge of potential NaCh mutations was minimal in Culex. Seeking pyrethroid resistance alleles in Culex, we evaluated a transect along the east coast of the United States with an NaCh-based genotyping tool that amplified a portion of the transcribed sequence containing kdr mutations and the intron immediately downstream of the mutation site. Three genotypes that are typically associated with pyrethroid resistance in insects have been identified in Culex pipiens complex mosquitoes in this study: susceptible wild type kds, the classical knock-down resistance Leu --> Phe mutation (Phe/kdr), and a second resistance mechanism, a Leu --> Ser mutation (Ser/kdr). Moreover, we observed heterozygotic individual mosquitoes possessing both kdr alleles. Results of this study advance our knowledge of the potential for pyrethroid insecticide resistance among the populations of Cx. pipiens complex in the United States.

Analysis of Transcriptome Differences between Resistant and Susceptible Strains of the Citrus Red Mite Panonychus citri (Acari: Tetranychidae)

“…In the P. citri database, we identified a number of unigenes encoding pesticide resistance target proteins (Table 2), of which sodium channel and GABA receptor were first reported in P. citri . Sodium channels have been shown to be targets of many pesticides such as pyrethroids [44], organophosphates [45], while GABA receptors are targets of ivermectin and avermectins [46]. We also identified mitochondrial cytochrome b genes (Table 2) that have previously been demonstrated as targets of bifenazate in P. citri [19].…”

Differential resistance of insect sodium channels with kdr mutations to deltamethrin, permethrin and DDT

“…With the scaling-up of malaria control efforts using indoor residual spraying with DDT and pyrethroids, and the use of pyrethroid treated bed nets, the continued selection of resistance may compromise control programmes (Czeher et al, 2008;Protopopoff et al, 2008). L1014S has also been identified in C. pipiens (Martinez-Torres et al, 1999), a vector of West Nile Virus, most recently in the USA (Zhou et al, 2009) and China (Chen et al, 2010). The L1014H substitution confirmed in field resistant strains of the agricultural pest H. virescens (Park and Taylor, 1997) and in common houseflies (Liu and Pridgeon, 2002;Rinkevich et al, 2006) constitutes a third 'natural' resistant allele at the L1014 locus.…”

Molecular Ecology of Pyrethroid Knockdown Resistance in Culex pipiens pallens Mosquitoes

“…In comparison, two forms of kdr mutations (L1014F and L1014S) were found in Cx. pipiens complex mosquitoes in the US [28]. However, information on the diversity and role of kdr alleles in pyrethroid resistance in Cx.…”