Molecular Entomology and Vector Control Research Laboratory, Public Health Division, Nigerian Institute of Medical Research, Akoka, Lagos, Nigeria.
Parasit Vectors. 2012 Jun 11;5:116. doi: 10.1186/1756-3305-5-116.
Resistance monitoring is essential in ensuring the success of insecticide based vector control programmes. This study was carried out to assess the susceptibility status of urban populations of Anopheles gambiae to carbamate insecticide being considered for vector control in mosquito populations previously reported to be resistant to DDT and permethrin.
Two - three day old adult female Anopheles mosquitoes reared from larval collections in 11 study sites from Local Government Areas of Lagos were exposed to test papers impregnated with DDT 4%, deltamethrin 0.05% and propoxur 0.1% insecticides. Additional tests were carried out to determine the susceptibility status of the Anopheles gambiae population to bendiocarb insecticide. Members of the A. gambiae complex, the molecular forms, were identified by PCR assays. The involvement of metabolic enzymes in carbamate resistance was assessed using Piperonyl butoxide (PBO) synergist assays. The presence of kdr-w/e and ace-1R point mutations responsible for DDT-pyrethroid and carbamate resistance mechanisms was also investigated by PCR.
Propoxur resistance was found in 10 out of the 11 study sites. Resistance to three classes of insecticides was observed in five urban localities. Mortality rates in mosquitoes exposed to deltamethrin and propoxur did not show any significant difference (P > 0.05) but was significantly higher (P < 0.05) in populations exposed to DDT. All mosquitoes tested were identified as A. gambiae s.s (M form). The kdr -w point mutation at allelic frequencies between 45%-77% was identified as one of the resistant mechanisms responsible for DDT and pyrethroid resistance. Ace-1R point mutation was absent in the carbamate resistant population. However, the possible involvement of metabolic resistance was confirmed by synergistic assays conducted.
Evidence of carbamate resistance in A. gambiae populations already harbouring resistance to DDT and permethrin is a clear indication that calls for the implementation of insecticide resistance management strategies to combat the multiple resistance identified.
在确保基于杀虫剂的病媒控制计划取得成功方面，抗药性监测至关重要。本研究旨在评估先前报道对滴滴涕和拟除虫菊酯具有抗药性的蚊虫种群中，拟用于病媒控制的氨基甲酸酯杀虫剂对城市冈比亚按蚊种群的敏感性状况。
从拉各斯地方政府区 11 个研究点的幼虫收集物中饲养的 2-3 天大的成年雌性按蚊，用浸渍滴滴涕 4%、溴氰菊酯 0.05%和残杀威 0.1%的测试纸进行接触测试。还进行了其他测试，以确定冈比亚按蚊种群对苯氧威杀虫剂的敏感性状况。应用聚合酶链反应（PCR）检测确定冈比亚按蚊复合体的成员、分子形式。用增效醚（PBO）协同测定法评估代谢酶在氨基甲酸酯抗性中的作用。还通过 PCR 检测了导致滴滴涕-拟除虫菊酯和氨基甲酸酯抗性机制的 kdr-w/e 和 ace-1R 点突变的存在。
在 11 个研究点中的 10 个点发现了残杀威抗性。在 5 个城市地区观察到对 3 类杀虫剂的抗性。暴露于溴氰菊酯和残杀威的蚊虫死亡率没有显著差异（P>0.05），但暴露于滴滴涕的蚊虫死亡率显著更高（P<0.05）。所有测试的蚊虫均被鉴定为冈比亚按蚊 s.s（M 型）。鉴定出 kdr-w 点突变在等位基因频率为 45%-77%之间，是导致滴滴涕和拟除虫菊酯抗性的一种抗性机制。在抗残杀威种群中不存在 ace-1R 点突变。然而，通过协同测定法证实了代谢抗性的可能参与。
已经对滴滴涕和拟除虫菊酯具有抗药性的冈比亚按蚊种群中存在氨基甲酸酯抗性的证据清楚地表明，需要实施杀虫剂抗药性管理策略来对抗已确定的多种抗性。
