Institut de Recherche en Sciences de la santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso.
Centre for Environmental Policy, Imperial College London, London, UK.
Malar J. 2019 Apr 2;18(1):113. doi: 10.1186/s12936-019-2747-5.
In the context of widespread mosquito resistance to currently available pesticides, novel, precise genetic vector control methods aimed at population suppression or trait replacement are a potentially powerful approach that could complement existing malaria elimination interventions. Such methods require knowledge of vector population composition, dynamics, behaviour and role in transmission. Here were characterized these parameters in three representative villages, Bana, Pala and Souroukoudingan, of the Sudano-Sahelian belt of Burkina Faso, a region where bed net campaigns have recently intensified.
From July 2012 to November 2015, adult mosquitoes were collected monthly using pyrethroid spray catches (PSC) and human landing catches (HLC) in each village. Larval habitat prospections assessed breeding sites abundance at each site. Mosquitoes collected by PSC were identified morphologically, and then by molecular technique to species where required, to reveal the seasonal dynamics of local vectors. Monthly entomological inoculation rates (EIR) that reflect malaria transmission dynamics were estimated by combining the HLC data with mosquito sporozoite infection rates (SIR) identified through ELISA-CSP. Finally, population and EIR fluctuations were fit to locally-collected rainfall data to highlight the strong seasonal determinants of mosquito abundance and malaria transmission in this region.
The principal malaria vectors found were in the Anopheles gambiae complex. Mosquito abundance peaked during the rainy season, but there was variation in vector species composition between villages. Mean survey HLC and SIR were similar across villages and ranged from 18 to 48 mosquitoes/person/night and from 3.1 to 6.6% prevalence. The resulting monthly EIRs were extremely high during the rainy season (0.91-2.35 infectious bites/person/day) but decreased substantially in the dry season (0.03-0.22). Vector and malaria transmission dynamics generally tracked seasonal rainfall variations, and the highest mosquito abundances and EIRs occurred in the rainy season. However, despite low residual mosquito populations, mosquitoes infected with malaria parasites remained present in the dry season.
These results highlight the important vector control challenge facing countries with high EIR despite the recent campaigns of bed net distribution. As demonstrated in these villages, malaria transmission is sustained for large parts of the year by a very high vector abundance and high sporozoite prevalence, resulting in seasonal patterns of hyper and hypo-endemicity. There is, therefore, an urgent need for additional vector control tools that can target endo and exophillic mosquito populations.
在当前广泛使用的杀虫剂对蚊子产生抗药性的情况下，新型、精确的基因媒介控制方法旨在抑制种群或替代特征，这是一种潜在的强大方法，可以补充现有的疟疾消除干预措施。此类方法需要了解媒介种群的组成、动态、行为和在传播中的作用。本研究在布基纳法索萨赫勒地带的三个代表性村庄（Bana、Pala 和 Souroukoudingan）对这些参数进行了描述，该地区最近加强了蚊帐运动。
2012 年 7 月至 2015 年 11 月，每月在每个村庄使用拟除虫菊酯喷雾捕获（PSC）和人体降落捕获（HLC）收集成年蚊子。幼虫栖息地勘察评估了每个地点的繁殖地丰度。通过形态学和分子技术对 PSC 收集的蚊子进行鉴定，如果需要，则鉴定到种，以揭示当地媒介的季节性动态。通过结合 HLC 数据和通过 ELISA-CSP 鉴定的疟原虫感染率（SIR），每月估计反映疟疾传播动态的昆虫接种率（EIR）。最后，将种群和 EIR 的波动拟合到当地收集的降雨数据上，以突出该地区蚊子丰度和疟疾传播的强烈季节性决定因素。
发现的主要疟疾媒介是冈比亚按蚊复合体。蚊子数量在雨季达到峰值，但村庄之间的媒介物种组成存在差异。村庄之间的平均调查 HLC 和 SIR 相似，范围为 18 至 48 只蚊子/人/夜和 3.1 至 6.6%的患病率。由此产生的每月 EIR 在雨季非常高（0.91-2.35 个传染性叮咬/人/天），但在旱季大幅下降（0.03-0.22）。蚊子和疟疾传播动态通常与季节性降雨变化相吻合，最高的蚊子数量和 EIR 出现在雨季。然而，尽管蚊子数量很少，但在旱季仍有感染疟原虫的蚊子存在。
这些结果突出了尽管最近开展了蚊帐分发运动，但在高 EIR 的国家面临的重要的蚊子控制挑战。正如这些村庄所表明的那样，由于非常高的媒介丰度和高疟原虫感染率，疟疾传播在很大程度上持续了一年，导致季节性高和低流行的模式。因此，迫切需要能够针对内栖和外栖蚊子种群的额外的蚊子控制工具。
