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，即非洲疟疾病媒所采用的战略，即在没有地表水的漫长旱季持续数月。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，表明疟疾媒介以休眠(消退)的形式在旱季持续存在，并进行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，《自然》杂志发表了我们基于媒介种群动力学对这个问题的研究。利用时间序列分析，我们提取并比较了媒介物种之间这些动态的季节成分。强烈的物种特有格局为持久化的媒介策略提供了特征。例如，密度在旱季达到高峰，加上紧随第一场雨后的种群快速增长，提供了coluzzii休眠的证据，而整个旱季完全没有种群，加上冈比亚按蚊正常种群增长的时间推迟了6-8周。(之后)与远距离迁徙是一致的。这些结果扩展了我们根据蚊子标记-释放-再捕获实验、空间分布的变化、空中蚊子采样(离地面100-200米)、繁殖活动、飞行活动、角质层碳氢化合物的季节变化以及对光周期和温度变化的反应而进行的其他研究。 基于这些发现，旨在(I)找到在旱季栖息的库鲁兹蚊子使用的隐蔽庇护所，(Ii)在高海拔地区(海拔100米)飞行的蚊子样本，使用系在氦气球上的捕蚊器，(Iii)确定促使蚊子在地面10-200米高空长途飞行的天气条件，等等。在过去的一年里，我们已经捕获了数十只在低空急流中飞行的蚊子，其中至少有14只冈比亚按蚊。作为这项工作的一部分，已经使用了20多个(气球级)氦储罐。 这些结果和正在进行的使用新方法的研究为疟疾和媒介生物学提供了新的见解。疟疾按蚊媒介和其他疾病媒介进行长途飞行，其中一些能够在旱季休眠，这一发现为基础和应用研究开辟了新的前沿。

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 vectors 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 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, Nature has published our investigation of this problem based on the vector population dynamics. Using time series analysis, we extracted and compared the seasonal components of these dynamics between the vector species. Strong species-specific pattern provided signatures for the vector strategy of persistence. For example, density peaks during the dry season, coupled with a rapid population growth closely following the first rain provided evidence for aestivation in A. coluzzii, whereas total absence throughout the dry season coupled with with 6-8 weeks delay in timing of normal population growth of A. gambiae s.s. (after than of A. coluzzii) was consistent with long-distance migration. These results extend other studies we have carried out based on mosquito mark-release-recapture experiments, variation in spatial distribution, aerial mosquito sampling (100-200 m above ground), seasonal changes in reproductive activity, flight activity, cuticular hydrocarbons, and responses to changes in photoperiod and temperature. Based on these findings, experiments designed to (i) find the hidden shelters used by aestivating A. coluzzii mosquitoes during the dry season, (ii) Sample mosquitoes flying in high altitutdes (>100 m above ground) using traps tethered to helium filled balloons, (iii) determine the weather conditions promoting long-distance mosquito flights 10--200 m above ground), among others. Over the past year, we have been able to collect dozens of mosquitoes flying in the lower jet stream among them at least 14 A. gambiae s.l. More than 20 tanks of (balloon grade) helium have been used as part of this work. These results and ongoing studies using novel approaches 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 are capable of dry-season dormancy open new frontiers of basic and applied research.