Antonio-Nkondjio Christophe, Tene Fossog Billy, Kopya Edmond, Poumachu Yacouba, Menze Djantio Benjamin, Ndo Cyrille, Tchuinkam Timoléon, Awono-Ambene Parfait, Wondji Charles S
Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), PO Box 288, Yaoundé, Cameroon.
Vector Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
Malar J. 2015 Apr 14;14:155. doi: 10.1186/s12936-015-0675-6.
The adaptation of malaria vectors to urban areas is becoming a serious challenge for malaria control. The study presents the evolution of pyrethroid resistance in mosquito populations from the cities of Douala and Yaoundé between 2010 and 2013.
Susceptibility tests to permethrin and deltamethrin were carried out with two- to four-day old unfed Anopheles gambiae sensu lato adults raised from larvae collected from the field. Mosquitoes resistant to permethrin and deltamethrin and control were screened to detect the presence of the kdr alleles using the TaqMan assays. Mosquitoes belonging to the An. gambiae complex were subjected to PCR assays designed for species and molecular forms identifications. The genomic region containing the upstream of intron-1 of the voltage-gated sodium channel was sequenced and compared between mosquitoes originating from different breeding habitats.
Anopheles gambiae s.l. specimens collected from the city of Douala were all Anopheles coluzzii. In Yaoundé, both An. gambiae and An. coluzzii were recorded. A rapid decrease of mosquito mortality to permethrin and deltamethrin was recorded between 2010 and 2013 in the two cities. The mortality rate varied from 80.3 to 22.3% and 94.4 to 59.7% for permethrin and deltamethrin, respectively. Both kdr alleles L1014F and L1014S were recorded. The frequency of kdr alleles increased rapidly over the study period, varying from 44 to 88.9% in Yaoundé and from 68 to 81% in Douala. The sequencing of a 1,228 bp region of intro-1 of the voltage-gated sodium channel revealed the presence of five different haplotypes. A high number of these haplotypes were recorded in An. coluzzii samples. No evidence for a recent selective sweep on intron-1 sequence within samples originating from different breeding habitat was detected using Fu's and Tajima Fs statistics.
The present study supports rapid evolution of pyrethroid resistance in vector populations from the cities of Douala and Yaoundé and calls for immediate action to fight against the increasing prevalence of pyrethroid-resistant mosquitoes.
疟疾媒介对城市环境的适应正成为疟疾防控的一项严峻挑战。本研究呈现了2010年至2013年期间杜阿拉和雅温得两市蚊虫种群中拟除虫菊酯抗性的演变情况。
对从野外采集的幼虫饲养出的2至4日龄未进食的冈比亚按蚊广义成虫进行氯菊酯和溴氰菊酯敏感性测试。对氯菊酯和溴氰菊酯抗性及对照蚊虫进行检测，使用TaqMan分析方法检测kdr等位基因的存在情况。对属于冈比亚按蚊复合体的蚊虫进行设计用于物种和分子型鉴定的PCR分析。对来自不同孳生地的蚊虫，对包含电压门控钠通道内含子-1上游的基因组区域进行测序并比较。
从杜阿拉市采集的冈比亚按蚊广义标本均为科氏按蚊。在雅温得，记录到了冈比亚按蚊和科氏按蚊。2010年至2013年期间，两市蚊虫对氯菊酯和溴氰菊酯的死亡率迅速下降。氯菊酯的死亡率从80.3%降至22.3%，溴氰菊酯的死亡率从94.4%降至59.7%。记录到了kdr等位基因L1014F和L1014S。在研究期间kdr等位基因频率迅速增加，在雅温得从44%增至88.9%，在杜阿拉从68%增至81%。对电压门控钠通道内含子-1的1228 bp区域测序显示存在五种不同单倍型。在科氏按蚊样本中记录到大量此类单倍型。使用傅氏和 Tajima Fs统计方法，未检测到来自不同孳生地的样本中内含子-1序列近期存在选择性清除的证据。
本研究支持杜阿拉和雅温得两市病媒种群中拟除虫菊酯抗性的快速演变，并呼吁立即采取行动应对拟除虫菊酯抗性蚊虫日益普遍的情况。
