Voltage-gated sodium channel intron polymorphism and four mutations comprise six haplotypes in an Aedes aegypti population in Taiwan

Abstract

Background Knockdown resistance (kdr) to dichlorodiphenyltrichloroethane (DDT) and pyrethroids is known to link amino acid substitutions in the voltage-gated sodium channel (VGSC) in Aedes aegypti . Dengue fever primarily transmitted by Ae . aegypti is an annual public health issue in Taiwan. Accordingly, pyrethroid insecticides have been heavily used for decades to control mosquito populations in the summer and autumn. In Taiwan, an Ae . aegypti population with two VGSC mutations, V1016G and D1763Y, was described previously. Methodology/Principal finding Aedes aegypti (G0) were collected in Tainan and Kaohsiung in southern Taiwan. The VGSC gene polymorphisms of the kdr mutations and the intron flanked by exons 20 and 21 were verified. The first generation offspring (G1) were used to measure the resistance level to cypermethrin, a pyrethroid insecticide currently used in Taiwan. In addition to V1016G and D1763Y, we describe two new mutations, S989P and F1534C, which have not been reported in Taiwan. Moreover, we also identify two types (groups A and B) of introns between exons 20 and 21. Intriguingly, the kdr mutations S989P, V1016G and D1763Y are strictly located on the haplotype harboring the group A intron, whereas F1534C links to the group B intron. When those data were taken together, we proposed the following six haplotypes for VGSC genes in Taiwan today: (i)S989-intron A-V1016-F1534-D1763, (ii)S989-intron A-V1016G-F1534-D1763, (iii)S989P-intron A-V1016G-F1534-D1763, (iv)S989-intron A-V1016G-F1534-D1763Y, (v)S989-intron B-V1016-F1534-D1763 and (vi)S989-intron B-V1016-F1534C-D1763. Triple heterozygous mutations of either S989P/V1016G/F1534C or V1016G/F1534C/D1763Y can be found in one single Ae . aegypti mosquito. The proportions of the VGSC mutations were relevant to cypermethrin resistance. Notably, the presence of S989P and V1016G in the population could be a helpful reference to predict the resistance level to cypermethrin. This is the first study to demonstrate the coexistence of four kdr mutations in a population of Ae . aegypti . Conclusions/Significance Four kdr mutations (S989P, V1016G, F1534C and D1763Y) and two intron forms (Group A and B) were commonly found in local Ae . aegypti populations in Taiwan.

Molecular Analysis of Targeted Insecticide Resistance Gene Mutations in field Aedes Aegypti and Culex Quinquefasciatus Mosquito Vectors of Arboviruses from Saudi Arabia

“…Among them, ve individuals with the SVC/SVC genotype possessed the type B intron, while the individual carrying the homozygous triple mutation (PGC/PGC) was coupled with the type A intron. In Taiwan, China, the F1534C was found to be strictly associated with the type B intron, and the V1016G mutation coexisted with the type A intron [38]. By contrast, in Africa, the point mutation at 1534 site was found to be strongly linked with the type A intron in Ghana, but only one heterozygote point mutation V1016I was recorded, except the F1534C mutations [67].…”

“…The intron polymorphism of VGSC could serve as a marker to study the evolution of kdr mutations [38,54]. Based on sequence size, the introns located between exons 20 and 21 were classi ed into type A (250 pb) and type B (234 pb) [54].…”

“…quinquefasciatus against chemical insecticides in Jeddah. For the bioassay test requires numerous live mosquitoes and time-consuming [38]. Early detection and characterization of target mutations of insecticide resistance genes, as potentially valuable molecular markers, can provide a reference to estimate the local insecticide resistance level for monitoring, planning and evaluation of vector control strategy [1,39,40].…”

Detection of Aedes aegypti Resistance towards Cypermethrin using Polymerase Chain Reaction (PCR) Techniques in Ambarawa Semarang Regency

“…Mutations in the gen VGSC caused by pyrethroid insecticide also occur in the world and in Indonesia. Resistance detection of by looking at mutations in the gen VGSC in the world occurs in populations of Aedes aegypti in Panama with the discovery of mutations for the first time in America in codons V1016G and I1011M (Murcia et al, 2019), and in Taiwan which detected mutations in the V1016G codon (28.03%) ), S989P (17.83%), F1534C (21.97%), and D1763Y (66.69%) (Chung, 2019). Similar mutations were also found in Indonesia in samples of Aedes aegypti originating from Palembang in studies showing the results of the gen V1016G with a DNA target of 82 bp (Ghiffari et al, 2013).…”

Molecular analysis of targeted insecticide resistance gene mutations in field Aedes aegypti and Culex quinquefasciatus mosquito vectors of arboviruses from Saudi Arabia

“…Among them, ve individuals with the SVC/SVC genotype possessed the type B intron, while the individual carrying the homozygous triple mutation (PGC/PGC) was coupled with the type A intron. In Taiwan, China, the F1534C was found to be strictly associated with the type B intron, and the V1016G mutation coexisted with the type A intron [38].…”