Abstract
BackgroundThe oriental rat flea, Xenopsylla cheopis, is the most efficient vector of the plague. Pyrethroid insecticides such as cypermethrin, cyhalothrin and deltamethrin have been often used to limit plague transmission via controlling the vector during outbreaks. However, this strategy is threatened by the development of insecticide resistance. Understanding the mechanisms underlying pyrethroid resistance is the prerequisite for successful flea control.MethodsPartial DNA sequences of X. cheopis voltage gated sodium channel (VGSC) gene were amplified from a total of 111 individuals, collected from a natural plague epidemic foci in Baise City, Guangxi Zhuang Autonomous Region of China. These DNA fragments were sequenced. The frequency and distribution of kdr mutations were assessed in four X. cheopis populations. The origin of kdr mutations was investigated by phylogenetic and network analysis.ResultsThe classical knockdown resistance (kdr) mutation (L1014F) was detected in four field populations at frequencies ranging between 0.021–0.241. The mutant homozygote was observed only in one of the four populations. Seven haplotypes were identified, with two of them carrying the resistance L1014F mutation. Phylogenetic tree and network analysis indicated that the L1014F allele was not singly originated. Based on polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) profiling, an easy-to-use and accurate molecular assay for screening individual fleas for the L1014F mutation was developed.ConclusionsTo our knowledge, this work represents the first report of the L1014F mutation in the plague vector X. cheopis. The incidence of the L1014F allele highlights the need of further studies on the phenotypic effect of this mutation in this plague vector. Early detection and monitoring of insecticide resistance is suggested in order to make effective control strategies in case of plague outbreaks in this region.
Highlights
The oriental rat flea, Xenopsylla cheopis, is the most efficient vector of the plague
The present study aimed to investigate possible pyrethroid resistance-conferring genetic mutations in the voltage gated sodium channel, and to assess the geographical distribution of resistant genotypes in X. cheopis populations
High similarity of voltage gated sodium channel (VGSC) was observed between X. cheopis with the dipteran Anopheles sinensis
Summary
The oriental rat flea, Xenopsylla cheopis, is the most efficient vector of the plague Pyrethroid insecticides such as cypermethrin, cyhalothrin and deltamethrin have been often used to limit plague transmission via controlling the vector during outbreaks. This strategy is threatened by the development of insecticide resistance. The bubonic plague, caused by the bacterium Yersinia pestis, is a highly transmissible zoonotic disease This disease is re-emerging with outbreaks occurring in many regions of the World [1]; 3248 cases were reported worldwide from 2010 to 2015, including 584 deaths [2]. The most efficient vector of the plague bacterium from rodents to humans is the flea species Xenopsylla cheopis; it has attracted increasing attention [3].
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