Dry Season Ecology of Malaria Vectors

尽管一个多世纪以来对疟疾进行了广泛的研究，但我们对病媒的了解仍然存在严重差距；这些差距也限制了我们在疟疾控制方面的成功。我们解决了一些最严重的差距，即非洲疟疾蚊子所采用的战略，即在没有地表水的漫长干旱季节持续数月。结合现场和实验室研究，我们的结果提供了令人信服的证据，表明疟疾媒介在当地以休眠(休眠)的形式在当地持续存在，并参与了可能超过数百公里的风助长途迁徙。媒介生物学的这些基本方面一直存在争议，到目前为止，由于证据不足而被忽视。传统的和新的疟疾和病媒控制战略不能忽视栖息和长途迁徙，因为它们可能阻碍或有助于最终结果。 今年，我们已经完成并发表了一项遗传学研究，以追踪萨赫勒地区雨季A.coluzzii种群的起源。在两年多的时间里，我们对包括几个时间点的13个蚊子样本进行了SNPs分析，发现从雨季结束到第一场雨后，蚊子种群的基因组成保持稳定，这为库鲁齐夜蛾的栖息提供了证据。然而，这项研究也揭示了在雨季后期，种群的基因组成发生了变化，这表明在雨季后期进行了长距离的迁徙。这项研究的局限性包括研究持续时间短(两年)和遗传能力有限(800个SNPs)。因此，我们与桑格中心(英国)合作，提交了4年来收集的2000只蚊子的全基因组测序。基于亚组基因分型的第一组结果显示，旱季后期的高峰期由蚊子组成，这些蚊子与唯一可能的迁徙来源(尼奥诺附近的大片水稻灌区，约为4月份)截然不同。150公里外)，从而支持了旱季后期高峰期由当地栖息的蚊子组成，这些蚊子从隐蔽的避难所出来补充营养储备(Dao等人)。2014年)。一旦获得完整的序列数据，就计划进行几次调查，从而得出关于这个问题和其他问题的全面答案。 关于成人饮食的影响，包括饮食限制和蛋白质/碳水化合物比例的变化对成年人寿命的影响，作为参与消退的一个因素的补充论文已经完成并发表(Faiman等人。2017年)。此外，一项关于光周期对库卢兹冬虫夏眠诱导的影响的研究(Hustis等人)。2017年)已接受出版。最后，对萨赫勒和河岸蚊子中蚊子微生物群落组成的季节变化进行了分析(KraJacich等人)。这篇论文很快就会提交到一份期刊上。 目前正在对在高海拔(离地面50-250米)飞行的蚊子进行分析，这些蚊子使用系在氦气球上的诱捕器。使用HYSPLIT气象模型，我们可以向前和向后追踪蚊子，并推断飞行轨迹和假定的来源种群。有了这个工具，我们可以完成至少3份出版物的分析和写作。除了按蚊，我们还收集了近3000只库蚊，其中许多可能是虫媒病毒的媒介。使用在我们实验室和Yvonne Linton小组在Walter Reed生物系统单位进行的COI条形码分析，我们识别了20个物种的1000只库蚊成员，其中有值得注意的虫媒病毒(例如，裂谷，西尼罗河)。此外，通过对在高海拔地区采集的昆虫进行分类，我们对影响粮食安全的农业害虫进行了鉴定和量化。其中包括将病毒和细菌传播到大米、玉米、高粱和谷子上的昆虫。还将对这些数据进行分析，以证明这种空中收集的价值，并将数据与科学界联系起来，并鼓励成员利用收集的数据进行自己的独立研究。 今年，我们完成了对马里1200只野生蚊子飞行能力的研究。初步结果显示，在9小时的测试中，蚊子可以持续飞行8小时。此外，正如预测的那样，冈比亚按蚊表现出比库卢齐按蚊更强的飞行能力。同样，飞行适应能力随季节变化，与高空采样一致。 最后，我们完成了第一个用稳定同位素标记天然蚊子的研究。在我们的实验室实验之后，我们已经在自然幼虫的地点用脱铀器丰富了水。我们第一次现场应用的结果表明，从这些蚊子中羽化出来的成虫表现出比自然浓度高出(&gt；4倍)的脱铀浓度，并在我们测试的最长时间内保持了浓缩物。这些结果非常令人鼓舞，可能会带来一种在时间和空间上追踪野生蚊子的有效方法。 这些结果和正在进行的使用新方法的研究(例如，高空采样、用于跟踪野生蚊子的稳定同位素浓缩)为疟疾和媒介生物学提供了新的见解。疟疾按蚊传播者和其他疾病传播者参与长途飞行的发现，以及一些传播疟疾的传播者，为基础研究和应用研究开辟了新的领域。

Despite extensive research on malaria for over a century, critical gaps remain in our understanding of the vectors; gaps that also limit our success in malaria control. We address some of the most critical gaps, namely the strategies used by African malaria mosquitoes to persist through the long dry season without surface waters for several months. Combining field and laboratory studies, our results provide compelling evidence that malaria vectors persist locally through the dry season by a form of dormancy (aestivation) and also engage in wind-assisted long-distance migration probably over hundreds of kilometers. These fundamental facets of vector biology have been controversial and, until now, were ignored due to insufficient evidence. Conventional and novel malaria and vector control strategies cannot afford to ignore aestivation and long-distance migration as processes that may hinder or aid the ultimate outcome. This year, we have completed and published a genetic study to trace the origin of A. coluzzii wet-season populations in the Sahel. Using SNPs in 13 mosquito samples including several time points over two years, we found that the genetic makeup of populations remained stable from the end of the wet season until after the first rains, providing evidence for aestivation in A. coluzzii. However, this study also revealed that during the late wet season, changes occur in the genetic makeup of populations suggesting long-range migration during the late-wet season. The limitations of this study included short duration of the study (two years) and limited genetic power (800 SNPs). Therefore, in collaboration with the Sanger Center (UK), we have submitted 2000 mosquitoes collected over 4 years to whole genome sequencing. The first set of results based on subset genotyping revealed that the late-dry season peak consists of mosquitoes that are distinctly different from the only likely source of migrants (the large rice irrigation area near Niono, approx. 150 km away), thus providing support that the late dry-season peak consists of locally aestivating mosquitoes that emerged from their hidden shelter to replenish nutritional reserves (Dao et al. 2014). Once the full sequence data be available several investigations leading to comprehensive answers on this and other questions are planned. Additional paper on the effect of adult diet, including dietary restriction and shifts in protein/carbohydrate ratio on adult longevity as a factor involved in aestivation has been completed and published (Faiman et al. 2017). Additionally, a study on the effect of photoperiod on the induction of aestivation in A. coluzzii (Huestis et al. 2017) has been accepted for publication. Finally, an analysis of seasonal variation in mosquito microbiome composition in Sahelian and riparian mosquitoes has been completed (Krajacich et al.) and the paper will be soon submitted to a journal. Analysis is in progress on mosquitoes flying in high altitudes (50-250 m above ground) using traps tethered to helium filled balloons. Using HYSPLIT meteorological models, we can track mosquitoes backwards and forward and infer flight trajectories and putative source populations. With this tool, we can complete the analysis and writing of at least 3 publications. In additional to anopheline mosquitoes, we collected nearly 3000 culicine mosquitoes, many of which might be vectors of arboviruses. Using COI barcode analysis carried out in our lab and in the Walter Reed Biosystematic Unit by Yvonne Linton group, we have identified 1000 culicine mosquitoes members of >20 species with notable arbovirus (e.g., Rift Valley, West Nile) vectors among them. Additionally, sorting insects collected in high altitude, we identify and quantify pest insects in agriculture affecting food security. These including insects that vector viruses and bacteria to rice, maize, sorghum, and millet. These will be also analyzed to demonstrate the value of this aerial collection and linked data to the scientific community and encourage members to use the collection their own independent studies. This year, we have completed a study on flight aptitude of >1200 wild mosquitoes in Mali. Preliminary reuslts reveal that mosquitoes can keep flying up to 8 hours in the 9 hours assay. Further as predicted A. gambiae has exhibited greater flight aptitude than A. coluzzii. Similarly, flight aptitude varied seasonally in agreement with high altitude sampling. Finally, we have completed the first study to marking natural mosquitoes with stable isotopes. Following our laboratory experiment, we have enriched water in natural larval sites with deutorium. Our results from this first field application have revealed that adult emerging from these mosquitoes have exhibited significantly (>4x) higher concentrations of deutorium over the natural concentration and retained the enrichcment through the longest time we have tested. These results are very encouraging and may lead to an effective method for tracking wild mosquitoes over time and space. These results and ongoing studies using novel approaches (e.g., high altitude sampling, the stable isotopes enrichment for tracking wild mosquitoes) provide fresh insights in malariology and vector biology. The findings that Anopheline vector of malaria and other disease vectors engage in long-distance flights and some aestivate open new frontiers of basic and applied research.