Emergence of hyper insecticide-resistant dengue vectors in Indochina Peninsula: threats of concomitant knockdown resistance mutations

Abstract

Aedes aegypti (Linnaeus, 1762) is the main mosquito vector for dengue and other arboviral infectious diseases. Control of this important vector highly relies on the use of insecticides, especially pyrethroids. Nevertheless, the development of pyrethroid resistance is a major obstacle to mosquito/disease control worldwide. Here, we focused on the mutations in the target site of pyrethroid insecticides, voltage-sensitive sodium channel (Vssc), and found that Ae. aegypti collected from Vietnam has the L982W allele in the Vssc at a high frequency (>79%). L982W mutation is located in the highly conserved region of Vssc that is associated with sodium-ion selectivity and permeation rate. Strains having the L982W allele showed similar or even higher levels of resistance to pyrethroids than those having V1016G, a typical knockdown resistance allele in Asia. Furthermore, concomitant mutations L982W+F1534C and V1016G+F1534C were confirmed, and strains having these multiple Vssc mutations exhibited incomparably higher levels of pyrethroid resistance than any other field population ever reported. Molecular modeling analysis confirmed that these concomitant mutant alleles could interfere with approaching pyrethroid to Vssc. Remarkably, >90% of Vssc of Ae. aegypti were occupied by these hyper insecticide-resistant haplotypes in Phnom Penh city, Cambodia. Analysis of whole Vssc coding genes suggested that Vsscs have evolved into stronger resistant forms efficiently through gene recombination events. At this point, L982W has never been detected in Vssc of Ae. aegypti from any other neighboring countries. We strongly emphasize the need to be vigilant about these strong resistance genes spreading to the world through Indochina Peninsula.

A next generation targeted amplicon sequencing method to screen for insecticide resistance mutations in Aedes aegypti populations reveals a rdl mutation in mosquitoes from Cabo Verde

“…We also have identified further polymorphisms, the majority in intronic regions, some in predicted splice regions or leading to synonymous changes, and only five non-synonymous amino acid substitutions in the ace-1 and vgsc genes. For example, the substitution V977L in the vgsc gene which is next to the previously reported L978W (position L982W in D. melanogaster) reported to confer resistance to pyrethroids [48,49]. There is also the synonymous PLOS NEGLECTED TROPICAL DISEASES variant in the ace-1 gene (T506T in Ae.…”

“…Four amino-acid substitutions (V977L, K1577T, N1595T, P1612H) were found in vgsc gene. Of interest is the substitution V977L as it is next to a known mutation, L978W, (homologous to position L982W in Drosophila melanogaster ), which is reported to confer resistance to pyrethroids [ 48 , 49 ].…”

“…For example, the substitution V977L in the vgsc gene which is next to the previously reported L978W (position L982W in D . melanogaster ) reported to confer resistance to pyrethroids [ 48 , 49 ]. There is also the synonymous variant in the ace-1 gene (T506T in Ae .…”