Shifting Patterns of Aedes aegypti Fine Scale Spatial Clustering in Iquitos, Peru

BackgroundEmpiric evidence shows that Aedes aegypti abundance is spatially heterogeneous and that some areas and larval habitats produce more mosquitoes than others. There is a knowledge gap, however, with regards to the temporal persistence of such Ae. aegypti abundance hotspots. In this study, we used a longitudinal entomologic dataset from the city of Iquitos, Peru, to (1) quantify the spatial clustering patterns of adult Ae. aegypti and pupae counts per house, (2) determine overlap between clusters, (3) quantify the temporal stability of clusters over nine entomologic surveys spaced four months apart, and (4) quantify the extent of clustering at the household and neighborhood levels.Methodologies/Principal FindingsData from 13,662 household entomological visits performed in two Iquitos neighborhoods differing in Ae. aegypti abundance and dengue virus transmission was analyzed using global and local spatial statistics. The location and extent of Ae. aegypti pupae and adult hotspots (i.e., small groups of houses with significantly [pAe. aegypti distribution was highly focal (most clusters do not extend beyond 30 meters) and that hotspots of high vector abundance were common on every survey date, but they were temporally unstable over the period of study.Conclusions/SignificanceOur findings have implications for understanding Ae. aegypti distribution and for the design of surveillance and control activities relying on household-level data. In settings like Iquitos, where there is a relatively low percentage of Ae. aegypti in permanent water-holding containers, identifying and targeting key premises will be significantly challenged by shifting hotspots of Ae. aegypti infestation. Focusing efforts in large geographic areas with historically high levels of transmission may be more effective than targeting Ae. aegypti hotspots.背景 经验证据表明，埃及伊蚊（Aedes aegypti）的种群丰度具有空间异质性，部分区域与幼虫滋生地可滋生出远多于其他区域的蚊虫。然而，针对此类埃及伊蚊丰度热点的时间持续性，目前仍存在认知空白。本研究采用秘鲁伊基托斯市的纵向昆虫学数据集，开展了四项分析：（1）量化每户埃及伊蚊成虫与蛹计数的空间聚集模式；（2）确定不同聚集簇之间的重叠情况；（3）量化间隔四个月开展的九次昆虫学调查期间，聚集簇的时间稳定性；（4）量化家庭与街区层面的聚集程度。 研究方法与主要结果 本研究对伊基托斯市两个在埃及伊蚊丰度与登革病毒（dengue virus）传播水平上存在差异的街区开展的13662户家庭昆虫学访视所获取的数据，采用全局与局域空间统计（spatial statistics）方法进行分析。结果显示，埃及伊蚊蛹与成虫热点区域（即单户蚊虫计数显著高于均值（p<0.05）的小型住户集群）的分布具有高度聚集性——多数集群的扩散范围未超过30米；且每次调查中均存在高媒介丰度热点，但在整个研究周期内，这些热点的时间稳定性较差。 研究结论与意义 本研究结果有助于深化对埃及伊蚊分布特征的理解，同时可为基于家庭层面数据的蚊虫监测与防控活动设计提供参考。在伊基托斯这类永久储水容器内埃及伊蚊占比较低的地区，识别并针对性处置重点滋生地，会因埃及伊蚊侵染热点的动态迁移而面临极大挑战。相较于靶向埃及伊蚊热点区域，将防控资源集中投向历史上传播水平较高的大片地理区域，或许能取得更优的防控效果。