One man's meat is another man's poison: exploring the effect of mass drug administration against schistosomes on the aquatic food web.

寄生虫是生态系统中不可或缺但未被充分认识的组成部分。特别是，在食物网中，它们可以改变链长和连接性，并且因为它们跨越营养水平，它们可以增加网的稳定性。在水生食物网中，寄生吸虫是一个特别重要的类群，水生软体动物通常是它们的中间宿主。在这些软体动物宿主中，寄生虫生命周期的无性生殖阶段发生，其特征在于随着最终宿主感染阶段的产生，寄生虫生物量迅速和大幅增加。因此，这些吸虫是重要的，因为它们对宿主软体动物有实质性的影响，而宿主软体动物本身是初级生产者和更高营养级之间的重要联系，并且因为软体动物的感染阶段的大量输出。这些感染阶段形成浮游动物的重要组成部分，是幼鱼和其他高等生物的重要食物来源。有趣的是，寄生虫也可以相互影响，因为不同的物种可以在共同感染的软体动物宿主中竞争资源，因此一种寄生虫物种丰度的任何变化都可能对其竞争对手产生涟漪反应。在吸虫中，血吸虫科是一个重要的家族，其中血吸虫属是值得注意的，因为它是该属的物种，对低收入到中等收入国家（LMIC）的人类健康构成严重威胁，每年有超过2.2亿人感染。由于该属的健康和经济重要性，大规模药物管理经常用于控制寄生虫。这样的大规模药物管理计划停止，或非常大幅度地减少，输出到水生环境中的软体动物感染阶段。这些大量和重复的寄生虫扰动，对水生食物网结构和/或功能的未探索的后果，将是这个博士学位的重点。具体来说，我们的目标是确定：1）寄生虫在湖泊的水生食物网中发挥什么作用。2）在多大程度上大规模的药物管理的人类改变食物网的结构和营养动力学。3）持续多久的任何扰动是在食物网。4）我们是否可以利用这种新的理解寄生虫在食物网生态学，以改善水生生态系统的健康，包括减少寄生虫的传播。

Parasites are an integral but under-recognised component of ecosystems. In particular, within food webs they can alter chain length and connectance and, because they act across trophic levels, they can increase web stability. In aquatic food webs the parasitic trematodes are a particularly important group, with aquatic molluscs, commonly acting as their intermediate hosts. Within these molluscan hosts the asexual reproductive phase of the parasites' life cycle occurs, characterised by a rapid and substantial increase in parasite biomass, as the definitive host infective stages are produced. These trematodes are therefore important, because of the substantial effects they have upon their host molluscs, which are themselves an important link between the primary producers and the higher trophic levels, and because of the substantial output of infective stages from the molluscs. These infective stages form a significant component of the zooplankton, an essential food source for juvenile fish and other higher organisms. Interestingly, the parasites can also affect one another, as different species can compete for resources inside coinfected molluscan hosts, so that any change in abundance of one parasite species can have ripple effects upon its competitors. Among the trematodes, the Schistosomatidae are a significant family, within which the genus Schistosoma is notable, as it is species from this genus that are a serious threat to human health in Low to Middle Income Countries (LMIC), with over 220 million people infected each year. Due to the health and economic importance of this genus, mass drug administration is frequently used to control parasites. Such mass drug administration programmes stop, or very substantially reduce, the output of mollusc infective stages into the aquatic environment. The unexplored consequences of these substantial and repeated parasite perturbations, upon aquatic food web structure and / or function, will be the focus of this PhD. Specifically, we aim to determine:1) What role schistosomes play in the aquatic food web of Lake Victoria.2) To what extent mass drug administration of humans alters the food web structure and trophic dynamics.3) How long-lasting any perturbations are within the food web.4) Whether we can leverage this new understanding of parasites in food web ecology to improve aquatic ecosystem health, including decreasing schistosome transmission.