Evaluation of the evolutionary genetics and population structure of Culex pipiens pallens in Shandong province, China based on knockdown resistance (kdr) mutations and the mtDNA-COI gene

Abstract

Background Mosquitoes are important vectors for a range of diseases, contributing to high rates of morbidity and mortality in the human population. Culex pipiens pallens is dominant species of Culex mosquito in northern China and a major vector for both West Nile virus and Bancroftian filariasis. Insecticide application were largely applied to control the mosquito-mediated spread of these diseases, contributing to increasing rates of resistance in the mosquito population. The voltage-gated sodium channel (Vgsc) gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr). While these kdr mutations are known to be critical to pyrethroid resistance, their evolutionary origins remain poorly understood. Clarifying the origins of these mutations is potential to guide further vector control and disease prevention efforts. Accordingly, the present study was designed to study the evolutionary genetics of kdr mutations and their association with the population structure of Cx. p. pallens in Shandong province, China. Methods Adult Culex females were collected from Shandong province and subjected to morphological identification under a dissection microscope. Genomic DNA were extracted from the collected mosquitoes, the Vgsc gene were amplified via PCR and sequenced to assess kdr allele frequencies, intron polymorphisms, and kdr codon evolution. In addition, population genetic diversity and related population characteristics were assessed by amplifying and sequencing the mitochondrial cytochrome C oxidase I (COI) gene. Results Totally, 263 Cx. p. pallens specimens were used for DNA barcoding and sequencing analyses to assess kdr allele frequencies in nine Culex populations. The kdr codon L1014 in the Vgsc gene identified two non-synonymous mutations (L1014F and L1014S) in the analyzed population. These mutations were present in the eastern hilly area and west plain region of Shandong Province. However, only L1014F mutation was detected in the southern mountainous area and Dongying city of Shandong Province, where the mutation frequency was low. Compared to other cities, population in Qingdao revealed significant genetic differentiation. Spatial kdr mutation patterns are likely attributable to some combination of prolonged insecticide-mediated selection coupled with the genetic isolation of these mosquito populations. Conclusions These data suggest that multiple kdr alleles associated with insecticide resistance are present within the Cx. p. pallens populations of Shandong Province, China. The geographical distributions of kdr mutations in this province are likely that the result of prolonged and extensive insecticide application in agricultural contexts together with frequent mosquito population migrations. In contrast, the low-frequency kdr mutation detected in central Shandong Province populations may originate from the limited selection pressure in this area and the relative genetic isolation. Overall, the study compares the genetic patterns revealed by a functional gene with a neutral marker and demonstrates the combined impact of demographic and selection factors on population structure.

Mutations and intron polymorphisms in voltage-gated sodium channel genes of different geographic populations of Culex pipiens pallens/Culex pipiens quinquefasciatus in China

“…The third was a base synonymous mutation of L1014L (TTA-CTA). Consistent with the results of existing studies [ 22 – 25 ], the L1014F mutation is not conserved. The existence of multiple mutation types at locus 1014 suggested that the mutations in Cx.…”

Evolution of knockdown resistance (kdr) mutations of Aedes aegypti and Aedes albopictus in Hainan Island and Leizhou Peninsula, China

“…albopictus population has high genetic exchange (Nm>1) with the other three populations in the city (TSSS, NYSS and ZJJC) (Table S3). Some studies on the evolution of the kdr gene in Culex quinquefasciatus suggested that the distribution of kdr mutations may be the result of widespread insecticide use and frequent population movements (Zang et al, 2023), and the findings of the present study also supported these conclusions.…”

DNA barcoding reveals an increased diversity within the genusCulex(Diptera: Culicidae) in Ireland

“…While this species has not been reported in Europe to date, the potential influence of trading practices between Asia and Europe do pose some concern. For example, Zang et al (2023) pointed out that the Hunagdao port in China acts as an important node for trade between over 450 ports, including those within Europe. Additionally, it has been proposed that hybrids of Cx.…”