Kushwah Raja Babu S, Dykes Cherry L, Kapoor Neera, Adak Tridibes, Singh Om P
National Institute of Malaria Research, Sector 8, Dwarka, Delhi, India.
School of Life Sciences, Indira Gandhi National Open University, Maidangarhi, New Delhi, India.
PLoS Negl Trop Dis. 2015 Jan 8;9(1):e3332. doi: 10.1371/journal.pntd.0003332. eCollection 2015 Jan.
Control of Aedes aegypti, the mosquito vector of dengue, chikungunya and yellow fever, is a challenging task. Pyrethroid insecticides have emerged as a preferred choice for vector control but are threatened by the emergence of resistance. The present study reports a focus of pyrethroid resistance and presence of two kdr mutations--F1534C and a novel mutation T1520I, in Ae. aegypti from Delhi, India.
METHODOLOGY/PRINCIPAL FINDINGS: Insecticide susceptibility status of adult-female Ae. aegypti against DDT (4%), deltamethrin (0.05%) and permethrin (0.75%) was determined using WHO's standard insecticide susceptibility kit, which revealed resistance to DDT, deltamethrin and permethrin with corrected mortalities of 35%, 72% and 76% respectively. Mosquitoes were screened for the presence of kdr mutations including those reported earlier (I1011V/M, V1016G/I, F1534C, D1794Y and S989P), which revealed the presence of F1534C and a novel mutation T1520I. Highly specific PCR-RFLP assays were developed for genotyping of these two mutations. Genotyping using allele specific PCR and new PCR-RFLP assays revealed a high frequency of F1534C (0.41-0.79) and low frequency of novel mutation T1520I (0.13). The latter was observed to be tightly linked with F1534C and possibly serve as a compensatory mutation. A positive association of F1534C mutation with DDT and deltamethrin resistance in Ae. aegypti was established. However, F1534C-kdr did not show significant protection against permethrin.
CONCLUSIONS/SIGNIFICANCE: The Aedes aegypti population of Delhi is resistant to DDT, deltamethrin and permethrin. Two kdr mutations, F1534C and a novel mutation T1520I, were identified in this population. This is the first report of kdr mutations being present in the Indian Ae. aegypti population. Highly specific PCR-RFLP assays were developed for discrimination of alleles at both kdr loci. A positive association of F1534C mutation with DDT and deltamethrin resistance was confirmed.
埃及伊蚊是登革热、基孔肯雅热和黄热病的传播媒介，对其进行控制是一项具有挑战性的任务。拟除虫菊酯类杀虫剂已成为病媒控制的首选，但受到抗药性出现的威胁。本研究报告了印度德里的埃及伊蚊中拟除虫菊酯抗性的一个集中区域以及两个击倒抗性（kdr）突变——F1534C和一个新突变T1520I的存在情况。
方法/主要发现：使用世界卫生组织的标准杀虫剂敏感性试剂盒测定成年雌性埃及伊蚊对滴滴涕（4%）、溴氰菊酯（0.05%）和氯菊酯（0.75%）的杀虫剂敏感性状况，结果显示对滴滴涕、溴氰菊酯和氯菊酯具有抗性，校正死亡率分别为35%、72%和76%。对蚊子进行了包括先前报道的那些（I1011V/M、V1016G/I、F1534C、D1794Y和S989P）在内的kdr突变筛查，结果显示存在F1534C和一个新突变T1520I。针对这两个突变的基因分型开发了高度特异性的PCR-RFLP检测方法。使用等位基因特异性PCR和新的PCR-RFLP检测方法进行基因分型显示F1534C的频率较高（0.41 - 0.79），新突变T1520I的频率较低（0.13）。观察到后者与F1534C紧密连锁，可能作为一种补偿性突变。在埃及伊蚊中确定了F1534C突变与对滴滴涕和溴氰菊酯抗性之间的正相关关系。然而，F1534C-kdr对氯菊酯并未显示出显著的抗性。
结论/意义：德里的埃及伊蚊种群对滴滴涕、溴氰菊酯和氯菊酯具有抗性。在该种群中鉴定出两个kdr突变，即F1534C和一个新突变T1520I。这是印度埃及伊蚊种群中存在kdr突变的首次报道。开发了高度特异性的PCR-RFLP检测方法用于区分两个kdr位点的等位基因。证实了F1534C突变与对滴滴涕和溴氰菊酯抗性之间的正相关关系。
