West African Centre for Cell Biology of Infectious Pathogens (WACCBIP) and Department of Biochemistry, Cell and Molecular, University of Ghana, Legon, Accra, Ghana.
Medical Research Council Unit, The Gambia at The London School of Hygiene & Tropical Medicine, Banjul, The Gambia.
PLoS One. 2021 Jun 24;16(6):e0241023. doi: 10.1371/journal.pone.0241023. eCollection 2021.
The scale-up of indoor residual spraying and long-lasting insecticidal nets, together with other interventions have considerably reduced the malaria burden in The Gambia. This study examined the biting and resting preferences of the local insecticide-resistant vector populations few years following scale-up of anti-vector interventions.
Indoor and outdoor-resting Anopheles gambiae mosquitoes were collected between July and October 2019 from ten villages in five regions in The Gambia using pyrethrum spray collection (indoor) and prokopack aspirator from pit traps (outdoor). Polymerase chain reaction assays were performed to identify molecular species, insecticide resistance mutations, Plasmodium infection rate and host blood meal.
A total of 844 mosquitoes were collected both indoors (421, 49.9%) and outdoors (423, 50.1%). Four main vector species were identified, including An. arabiensis (indoor: 15%, outdoor: 26%); An. coluzzii (indoor: 19%, outdoor: 6%), An. gambiae s.s. (indoor: 11%, outdoor: 16%), An. melas (indoor: 2%, outdoor: 0.1%) and hybrids of An. coluzzii-An. gambiae s.s (indoors: 3%, outdoors: 2%). A significant preference for outdoor resting was observed in An. arabiensis (Pearson X2 = 22.7, df = 4, P<0.001) and for indoor resting in An. coluzzii (Pearson X2 = 55.0, df = 4, P<0.001). Prevalence of the voltage-gated sodium channel (Vgsc)-1014S was significantly higher in the indoor-resting (allele freq. = 0.96, 95%CI: 0.78-1, P = 0.03) than outdoor-resting (allele freq. = 0.82, 95%CI: 0.76-0.87) An. arabiensis population. For An. coluzzii, the prevalence of most mutation markers was higher in the outdoor (allele freq. = 0.92, 95%CI: 0.81-0.98) than indoor-resting (allele freq. = 0.78, 95%CI: 0.56-0.86) mosquitoes. However, in An. gambiae s.s., the prevalence of Vgsc-1014F, Vgsc-1575Y and GSTe2-114T was high (allele freq. = 0.96-1), but did not vary by resting location. The overall sporozoite positivity rate was 1.3% (95% CI: 0.5-2%) in mosquito populations. Indoor-resting An. coluzzii had mainly fed on human blood while indoor-resting An. arabiensis fed on animal blood.
In this study, high levels of resistance mutations were observed that could be influencing the mosquito populations to rest indoors or outdoors. The prevalent animal-biting behaviour demonstrated in the mosquito populations suggest that larval source management could be an intervention to complement vector control in this setting.
室内滞留喷洒和长效驱虫蚊帐的推广，以及其他干预措施，大大降低了冈比亚的疟疾负担。本研究调查了抗蚊措施推广几年后，当地抗药性媒介种群的叮咬和栖息偏好。
2019 年 7 月至 10 月，使用除虫菊酯喷雾采集器（室内）和坑陷阱 Prokopack 吸气器（室外），从冈比亚五个地区的十个村庄收集室内和室外栖息的冈比亚按蚊。聚合酶链反应检测用于鉴定分子种、杀虫剂抗性突变、疟原虫感染率和宿主血液餐。
共采集了 844 只蚊子，室内采集 421 只（49.9%），室外采集 423 只（50.1%）。共鉴定出 4 种主要媒介种，包括阿拉伯按蚊（室内：15%，室外：26%）；库蚊（室内：19%，室外：6%）；冈比亚按蚊 s.s.（室内：11%，室外：16%）；淡色库蚊（室内：2%，室外：0.1%）和库蚊-冈比亚按蚊 s.s. 杂交种（室内：3%，室外：2%）。阿拉伯按蚊明显偏好室外栖息（皮尔逊卡方=22.7，自由度=4，P<0.001），库蚊明显偏好室内栖息（皮尔逊卡方=55.0，自由度=4，P<0.001）。室内栖息的电压门控钠离子通道（Vgsc）-1014S 发生率明显高于室外栖息（等位基因频率=0.96，95%置信区间：0.78-1，P=0.03）的阿拉伯按蚊种群。对于库蚊，大多数突变标记的流行率在室外（等位基因频率=0.92，95%置信区间：0.81-0.98）高于室内栖息（等位基因频率=0.78，95%置信区间：0.56-0.86）的库蚊。然而，在冈比亚按蚊 s.s.中，Vgsc-1014F、Vgsc-1575Y 和 GSTe2-114T 的流行率很高（等位基因频率=0.96-1），但不受栖息位置的影响。疟原虫感染率为 1.3%（95%置信区间：0.5-2%）。室内栖息的库蚊主要以人血为食，而室内栖息的阿拉伯按蚊则以动物血为食。
本研究观察到高水平的抗性突变，这可能影响蚊子种群在室内或室外栖息。蚊子种群中普遍存在的动物叮咬行为表明，幼虫源管理可能是该环境中补充蚊虫控制的一种干预措施。
