Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591, Yaoundé, Cameroon.
Malar J. 2018 Aug 30;17(1):317. doi: 10.1186/s12936-018-2467-2.
Malaria vectors are increasingly developing resistance to insecticides across Africa. The impact of such resistance on the continued effectiveness of insecticide-based interventions remains unclear due to poor characterization of vector populations. This study reports the characterization of malaria vectors at Mibellon, a selected site in Cameroon for experimental hut study, including species composition, Plasmodium infection rate, resistance profiles and mechanisms.
Indoor resting blood-fed Anopheles mosquitoes were collected from houses at Mibellon in 2017 and forced to lay eggs to generate F adult mosquitoes. Insecticides susceptibility bioassays were performed on the F adult mosquitoes following the WHO protocol to assess resistance profile to insecticides. The molecular basis of resistance and Plasmodium infection rate were investigated using TaqMan genotyping.
Anopheles funestus sensu stricto (s.s.) was predominant in Mibellon (80%) followed by Anopheles gambiae s.s. (20%). High levels of resistance to pyrethroids and organochlorides were observed for both species. Moderate resistance was observed against bendiocarb (carbamate) in both species, but relatively higher in An. gambiae s.s. In contrast, full susceptibility was recorded for the organophosphate malathion. The PBO synergist assays with permethrin and deltamethrin revealed a significant recovery of the susceptibility in Anopheles funestus s.s. population (48.8 to 98.1% mortality and 38.3 to 96.5% mortality, respectively). The DDT/pyrethroid 119F-GSTe2 resistant allele (28.1%) and the dieldrin 296S-RDL resistant (9.7%) were detected in An. funestus s.s. The high pyrethroid/DDT resistance in An. gambiae correlated with the high frequency of 1014F knockdown resistance allele (63.9%). The 1014S-kdr allele was detected at low frequency (1.97%). The Plasmodium infection rate was 20% in An. gambiae, whereas An. funestus exhibited an oocyst rate of 15 and 5% for the sporozoite rate.
These results highlight the increasing spread of insecticide resistance and the challenges that control programmes face to maintain the continued effectiveness of insecticide-based interventions.
疟疾媒介在非洲各地对杀虫剂的抗药性日益增强。由于对媒介种群的特征描述不佳，这种抗药性对基于杀虫剂的干预措施的持续有效性的影响仍不清楚。本研究报告了喀麦隆 Mibellon 一个选定的实验小屋研究地点的疟疾媒介的特征，包括物种组成、疟原虫感染率、抗药性概况和机制。
2017 年，从 Mibellon 的房屋内采集室内休息吸血的按蚊，并强迫其产卵以产生 F 代成蚊。按照世界卫生组织的方案对 F 代成蚊进行杀虫剂敏感性生物测定，以评估对杀虫剂的抗药性概况。使用 TaqMan 基因分型法研究抗药性的分子基础和疟原虫感染率。
在 Mibellon，按蚊属（Anopheles）中最主要的是按蚊属（Anopheles）f. （s.s.）（80%），其次是按蚊属（Anopheles）g. （s.s.）（20%）。两种蚊种均对拟除虫菊酯和有机氯表现出高水平的抗药性。两种蚊种对苯氧威（氨基甲酸酯）均表现出中等程度的抗药性，但在按蚊属（An. gambiae s.s.）中相对较高。相比之下，有机磷酸酯马拉硫磷则表现出完全的敏感性。用增效剂 PBO 对氯菊酯和溴氰菊酯进行的测定表明，按蚊属（Anopheles）f. （s.s.）种群的敏感性显著恢复（死亡率分别为 48.8%至 98.1%和 38.3%至 96.5%）。在按蚊属（An. funestus s.s.）中检测到滴滴涕/拟除虫菊酯 119F-GSTe2 抗性等位基因（28.1%）和狄氏剂 296S-RDL 抗性（9.7%）。按蚊属（An. gambiae）中较高的拟除虫菊酯/滴滴涕抗药性与 1014F 击倒抗性等位基因（63.9%）的高频有关。1014S-kdr 等位基因的检出频率较低（1.97%）。按蚊属（An. gambiae）的疟原虫感染率为 20%，而按蚊属（An. funestus）的卵囊率为 15%，孢子体率为 5%。
这些结果突出表明，杀虫剂抗药性的传播日益广泛，以及控制方案在维持基于杀虫剂的干预措施的持续有效性方面面临的挑战。
