Freshwater pollution and the links to the distribution of Schistosoma host snails in Western Kenya

血吸虫病是仅次于疟疾的第二紧迫的热带疾病，全世界有2.18亿人感染。它是由血吸虫属吸虫引起的，它以人类为最终宿主，以planorbidae科淡水蜗牛为中间宿主。撒哈拉以南非洲血吸虫病感染热点地区的典型特点是广泛的农业和暴雨。在这种情况下，地表径流很有可能将农药从农田冲到邻近的淡水中。这种农用化学品污染影响了大型无脊椎动物群落结构，从而有利于血吸虫的高耐受性寄主蜗牛。目前，全球控制战略一般依赖于通过人类治疗，用药物杀死藏在人类宿主体内的成虫来控制发病率，但它不能防止再次感染。因此，需要限制淡水生物群落的再感染。这就是SENTINEL项目的用武之地。在第一个SENTINEL项目中，我们已经通过实地监测和实验室实验确定了增加寄主蜗牛发生的环境因素，即农药污染和富营养化。现在，在后续项目sentinel - 2中，我们的目标是了解与描述蜗牛感染率相关的环境因素。为此，我们将调查全年寄主蜗牛及其血吸虫的时空种群动态和再定殖情况。此外，我们还研究了农药污染的时空变化及其与大型无脊椎动物群落结构、寄主蜗牛丰度和寄主蜗牛体内血吸虫的时间动态的关系。最后，我们还旨在研究额外的环境应激源对寄主蜗牛体内寄生虫负荷动态的影响。我们将通过实地研究和实验室调查来解决所有的研究问题。我们预计，SENTINEL-1和SENTINEL-2的综合结果将全面揭示基于主流环境条件下驱动寄生虫及其宿主发生和感染率的生态毒理学过程和相互关系。该项目将结合三个德国和三个肯尼亚研究机构的专业知识，包括复杂环境样本的化学分析、不同生物组织水平的生态毒理学效应分析、热带病媒物种和相关淡水群落的生态学以及吸虫物种的分子测定。

Schistosomiasis is the second most pressing tropical disease after malaria, with 218 million people infected worldwide. It is caused by trematodes of the genus Schistosoma sp. which parasitize humans as their definitive host and freshwater snails of the family planorbidae as their intermediate hosts. Hot spots of schistosomiasis infections in Sub-Saharan Africa are typically characterized by extensive agriculture and heavy rainfalls. In such conditions, there is a high risk of surface run-off that washes pesticides from agricultural fields into adjacent freshwaters. This agrochemical pollution affects the macro-invertebrate community structure such that this favours highly tolerant host snails of Schistosoma. Currently, the global control strategies generally rely on morbidity control through human treatment with drugs that kill adult worms harboured in human hosts, but it cannot prevent the re-infection. Accordingly, re-infection from freshwater biotopes needs to be restricted. This is where the SENTINEL project comes in. In the first SENTINEL project, we have already identified those environmental factors through field monitoring as well as laboratory experiment that increase the occurrence of the host snails – namely pesticide pollution and eutrophication. Now, in the follow-up project SENTINEL-ll, we aim to understand the environmental factors that are relevant for describing the infection rate of snails. For this, we will investigate the spatiotemporal population dynamics and recolonization of host snails, and their schistosomes throughout the year. Additionally, we aim to investigate spatiotemporal variation in pesticide pollution and its association with macroinvertebrate community structure, abundance of host snails and the temporal dynamics of schistosomes in the host snails. Finally, we also aim to investigate the effect of additional environmental stressors on the dynamics of parasite burden in host snails. We will address all of the research questions through field studies as well as laboratory investigations. We anticipate that the combined results of SENTINEL-1 and SENTINEL-2 will draw a complete picture of the ecotoxicological processes and interrelations driving the occurrence and infection rate of the parasites and their host based on the prevailing environmental conditions. This project will combine the expertise of three German and three Kenyan research institutes including the chemical analysis of complex environmental samples, the analysis of ecotoxicological effects across different biological organization levels, the ecology of tropical vector species and associated freshwater communities, and the molecular determination of the trematode species.