National Malaria Elimination Centre, Chainama Hills Hospital Grounds, PO Box 32509, Lusaka, Zambia.
Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L35QA, United Kingdom.
Parasit Vectors. 2018 Oct 11;11(1):544. doi: 10.1186/s13071-018-3121-0.
Across most of sub-Saharan Africa, malaria is transmitted by mosquitoes from the Anopheles gambiae complex, comprising seven morphologically indistinguishable but behaviourally-diverse sibling species with ecologically-distinct environmental niches. Anopheles gambiae and An. arabiensis are the mostly widely distributed major malaria vectors within the complex, while An. quadriannulatus is sparsely distributed.
Indoor residual spraying (IRS) with the organophosphate pirimiphos-methyl (PM) was conducted four times between 2011 and 2017 in the Luangwa Valley, south-east Zambia. Anopheles mosquitoes were repeatedly collected indoors by several experiments with various objectives conducted in this study area from 2010 onwards. Indoor mosquito collection methods included human landing catches, Centres for Disease Control and Prevention miniature light traps and back pack aspirators. Anopheles gambiae complex mosquitoes were morphologically identified to species level using taxonomic keys, and to molecular level by polymerase chain reaction. These multi-study data were collated so that time trends in the species composition of this complex could be assessed.
The proportion of indoor An. gambiae complex accounted for by An. quadriannulatus declined from 95.1% to 69.7% following two application PM-IRS rounds with an emulsifiable concentrate formulation from 2011 to 2013, while insecticidal net utilisation remained consistently high throughout that period. This trend continued after two further rounds of PM-IRS with a longer-lasting capsule suspension formulation in 2015 and 2016/2017, following which An. quadriannulatus accounted for only 4.5% of the complex. During the same time interval there was a correspondingly steady rise in the proportional contribution of An. arabiensis to the complex, from 3.9 to 95.1%, while the contribution of nominate An. gambiae remained stable at ≤ 0.9%.
It seems likely that An. arabiensis is not only more behaviourally resilient against IRS than An. gambiae, but also than An. quadriannulatus populations exhibiting indoor-feeding, human-feeding and nocturnal behaviours that are unusual for this species. Routine, programmatic entomological monitoring of dynamic vector population guilds will be critical to guide effective selection and deployment of vector control interventions, including supplementary measures to tackle persisting vectors of residual malaria transmission like An. arabiensis.
在撒哈拉以南非洲的大部分地区，疟疾是由冈比亚按蚊复合体中的蚊子传播的，该复合体由七种形态上无法区分但行为上多样化的具有生态上明显不同的环境小生境的姐妹种组成。冈比亚按蚊和阿拉伯按蚊是该复合体中分布最广的主要疟疾媒介，而四斑按蚊则分布稀疏。
2011 年至 2017 年，在赞比亚东南部的卢安瓜谷，使用有机磷杀虫剂吡虫啉（PM）进行了四次室内残留喷洒（IRS）。自 2010 年以来，在该研究区域进行了多项旨在实现不同目标的实验，反复在室内采集按蚊。室内蚊子采集方法包括人体诱蚊器、美国疾病控制与预防中心微型诱蚊灯和背包式吸气器。冈比亚按蚊复合体蚊子采用分类学关键技术进行形态学鉴定，采用聚合酶链反应进行分子鉴定。这些多研究数据被整理，以便评估该复合体物种组成的时间趋势。
2011 年至 2013 年，使用可乳化浓缩剂制剂进行了两轮 PM-IRS 后，室内冈比亚按蚊复合体中四斑按蚊的比例从 95.1%下降到 69.7%，而同期杀虫网使用率一直保持较高水平。2015 年和 2016/2017 年，使用长效胶囊悬浮剂进行了另外两轮 PM-IRS 后，这一趋势仍在继续，此后四斑按蚊仅占复合体的 4.5%。在此期间，按蚊属 Arabiensis 对复合体的比例相应稳步上升，从 3.9%上升到 95.1%，而命名的冈比亚按蚊的比例保持稳定，≤0.9%。
似乎表明，阿拉伯按蚊不仅对 IRS 的行为抵抗力比冈比亚按蚊更强，而且比表现出室内取食、人类取食和夜间行为的四斑按蚊种群更具抵抗力，这些行为对该物种来说是不寻常的。常规的、计划性的媒介种群监测对于指导有效的选择和部署媒介控制干预措施至关重要，包括补充措施，以解决持续存在的残留疟疾传播媒介，如阿拉伯按蚊。
