First detection of the kdr mutation (L1014F) in the plague vector Xenopsylla cheopis (Siphonaptera: Pulicidae)
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Published on: February 28, 2015
Nian Liu1, Xiangyang Feng2, Mei Li1
1State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.
Background:
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. However, this strategy is threatened by the development of insecticide resistance. Understanding the mechanisms underlying pyrethroid resistance is the prerequisite for successful flea control.
Methods:
Partial 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.
Results:
The 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.
Conclusions:
To 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.
Insights
The L1014F mutation, a mechanism of pyrethroid resistance, was detected in the oriental rat flea (Xenopsylla cheopis) populations. This finding necessitates monitoring insecticide resistance for effective plague control.
Area of Science:
- Vector-borne disease research
- Medical entomology
- Molecular parasitology
Background:
- The oriental rat flea (Xenopsylla cheopis) is a primary vector for plague transmission.
- Pyrethroid insecticides are crucial for controlling flea populations during outbreaks.
- Insecticide resistance in fleas poses a significant threat to plague control strategies.
Purpose of the Study:
- To investigate the presence and frequency of pyrethroid resistance mutations in Xenopsylla cheopis populations.
- To understand the genetic basis and origin of insecticide resistance in this plague vector.
- To develop a molecular tool for detecting insecticide resistance in fleas.
Main Methods:
- Amplification and sequencing of voltage-gated sodium channel (VGSC) gene fragments from 111 Xenopsylla cheopis individuals.
- Assessment of knockdown resistance (kdr) mutation frequencies and distribution across four populations.
- Phylogenetic and network analyses to determine the origin of kdr mutations.
Main Results:
- The L1014F kdr mutation was identified in all four sampled populations, with frequencies ranging from 0.021 to 0.241.
- Seven haplotypes were found, two of which harbored the L1014F resistance mutation.
- Phylogenetic analysis indicated that the L1014F allele did not arise from a single origin.
Conclusions:
- This study reports the L1014F mutation in Xenopsylla cheopis, the plague vector, for the first time.
- The prevalence of the L1014F allele underscores the need for further research into its phenotypic effects.
- Early detection and monitoring of insecticide resistance are recommended for effective plague outbreak management.
