Santolamazza Federica, Calzetta Maria, Etang Josiane, Barrese Elena, Dia Ibrahima, Caccone Adalgisa, Donnelly Martin J, Petrarca Vincenzo, Simard Frederic, Pinto Joao, della Torre Alessandra
Istituto Pasteur-Fondazione Cenci-Bolognetti, Università La Sapienza, Rome, Italy.
Malar J. 2008 Apr 29;7:74. doi: 10.1186/1475-2875-7-74.
Knock-down resistance (kdr) to DDT and pyrethroids in the major Afrotropical vector species, Anopheles gambiae sensu stricto, is associated with two alternative point mutations at amino acid position 1014 of the voltage-gated sodium channel gene, resulting in either a leucine-phenylalanine (L1014F), or a leucine-serine (L1014S) substitution. In An. gambiae S-form populations, the former mutation appears to be widespread in west Africa and has been recently reported from Uganda, while the latter, originally recorded in Kenya, has been recently found in Gabon, Cameroon and Equatorial Guinea. In M-form populations surveyed to date, only the L1014F mutation has been found, although less widespread and at lower frequencies than in sympatric S-form populations.
Anopheles gambiae M- and S-form specimens from 19 sites from 11 west and west-central African countries were identified to molecular form and genotyped at the kdr locus either by Hot Oligonucleotide Ligation Assay (HOLA) or allele-specific PCR (AS-PCR).
The kdr genotype was determined for about 1,000 An. gambiae specimens. The L1014F allele was found at frequencies ranging from 6% to 100% in all S-form samples (N = 628), with the exception of two samples from Angola, where it was absent, and coexisted with the L1014S allele in samples from Cameroon, Gabon and north-western Angola. The L1014F allele was present in M-form samples (N = 354) from Benin, Nigeria, and Cameroon, where both M- and S-forms were sympatric.
The results represent the most comprehensive effort to analyse the overall distribution of the L1014F and L1014S mutations in An. gambiae molecular forms, and will serve as baseline data for resistance monitoring. The overall picture shows that the emergence and spread of kdr alleles in An. gambiae is a dynamic process and that there is marked intra- and inter-form heterogeneity in resistance allele frequencies. Further studies are needed to determine: i) the importance of selection pressure exerted by both agricultural and public health use of pyrethroid insecticides, ii) the phenotypic effects, particularly when the two mutations co-occur; and iii) the epidemiological importance of kdr for both pyrethroid- and DDT-based malaria control operations, particularly if/when the two insecticides are to be used in concert.
在非洲热带地区主要病媒物种冈比亚按蚊（Anopheles gambiae sensu stricto）中，对滴滴涕和拟除虫菊酯的击倒抗性（kdr）与电压门控钠通道基因第1014位氨基酸的两种替代点突变相关，导致亮氨酸 - 苯丙氨酸（L1014F）或亮氨酸 - 丝氨酸（L1014S）替代。在冈比亚按蚊S型种群中，前一种突变似乎在西非广泛存在，最近在乌干达也有报道，而后一种突变最初记录于肯尼亚，最近在加蓬、喀麦隆和赤道几内亚被发现。在迄今为止调查的M型种群中，仅发现了L1014F突变，尽管其分布范围不如同域分布的S型种群广泛，频率也较低。
对来自11个西非和中西部非洲国家19个地点的冈比亚按蚊M型和S型标本进行分子分型，并通过热寡核苷酸连接测定法（HOLA）或等位基因特异性PCR（AS-PCR）在kdr位点进行基因分型。
确定了约1000只冈比亚按蚊标本的kdr基因型。在所有S型样本（N = 628）中，L1014F等位基因的频率范围为6%至100%，安哥拉的两个样本除外，这两个样本中不存在该等位基因，并且在喀麦隆、加蓬和安哥拉西北部的样本中与L1014S等位基因共存。L1014F等位基因存在于来自贝宁、尼日利亚和喀麦隆的M型样本（N = 354）中，这些地方M型和S型是同域分布的。
这些结果代表了分析冈比亚按蚊分子型中L1014F和L1014S突变总体分布的最全面努力，并将作为抗性监测的基线数据。总体情况表明，冈比亚按蚊中kdr等位基因的出现和传播是一个动态过程，并且抗性等位基因频率在型内和型间存在显著异质性。需要进一步研究以确定：i）拟除虫菊酯类杀虫剂在农业和公共卫生使用中施加的选择压力的重要性；ii）表型效应，特别是当两种突变同时发生时；以及iii）kdr对基于拟除虫菊酯和滴滴涕的疟疾控制行动的流行病学重要性，特别是如果/当两种杀虫剂协同使用时。
