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Published on: February 28, 2015
The double-mutation（M918I + L1014F）kdr allele is fixed in Cimex hemipterus populations in Guangxi, China
Yuhan Zhao1, Xiangyang Feng2, Mei Li1
1State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China.
Insights
A new double-mutation knockdown resistance (kdr) allele (M918I + L1014F) in voltage-gated sodium channel (VGSC) genes is 100% prevalent in Chinese tropical bed bug populations, questioning pyrethroid efficacy.
Area of Science:
- Molecular Entomology
- Insecticide Resistance Genetics
- Population Genetics
Background:
- Knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC) gene are a primary mechanism of pyrethroid resistance in the tropical bed bug, Cimex hemipterus.
- Previous studies have identified various kdr mutations globally, but none have been reported in Chinese populations of C. hemipterus.
Purpose of the Study:
- To investigate the presence and frequency of kdr mutations in tropical bed bug populations from the Guangxi Zhuang Autonomous Region of China.
- To assess the genetic diversity of C. hemipterus populations in this region using mitochondrial DNA markers.
Main Methods:
- Genomic DNA was extracted from adult C. hemipterus specimens collected from six locations in Guangxi.
- The voltage-gated sodium channel (VGSC) gene was amplified and sequenced to identify kdr mutations.
- Mitochondrial cytochrome c oxidase I (COI) gene was sequenced to analyze genetic diversity and population structure.
Main Results:
- A double-mutation kdr allele (M918I + L1014F) was identified in all six C. hemipterus populations.
- This resistant allele was fixed (100% frequency) across all examined populations.
- Analysis of the COI gene revealed very low genetic diversity, with only two haplotypes found among 48 individuals, suggesting a recent single origin.
Conclusions:
- The widespread and fixed double-mutation kdr allele in Chinese tropical bed bug populations raises serious concerns about the effectiveness of current pyrethroid-based control strategies.
- The extremely low genetic diversity observed suggests a recent bottleneck event or a single introduction, facilitating the rapid spread of the resistant allele.
Abstract:
Four putative knockdown resistance (kdr) mutations have been documented in the voltage-gated sodium channel (VGSC) gene of Cimex hemipterus from several countries. However, no information regarding kdr mutations in any Chinese tropical bed bug population is available to date. In this study, a double-mutation（M918I + L1014F）kdr allele was identified in six C. hemipterus populations across Guangxi Zhuang Autonomous Region of China. The frequency of this allele was 100% in all the six examined populations. In addition, only two cytochrome c oxidase I (COI) gene haplotypes, with one synonymous nucleotide variation, were identified in a total of 48 individuals from six locations. The fixation and broad geographic distribution of this resistant allele questions the continued use of pyrethroids in the treatment of tropical bed bug infestations. The very low genetic diversity within and among these populations indicates that these bed bugs may have a single origin.
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