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一个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，因为它们在营养水平上起作用，可以增加网络的稳定性。在水生食物网中，寄生吸虫是一个特别重要的类群，水生软体动物通常充当它们的中间宿主。在这些软体动物体内，寄生虫生命周期的无性繁殖阶段发生，其特征是寄生虫生物量迅速和大幅增加，因为最终的宿主感染阶段产生了。因此，这些吸虫很重要，因为它们对寄主软体动物有实质性的影响，而寄主软体动物本身就是初级生产者和较高营养水平之间的重要纽带，而且软体动物感染阶段的产量很大。这些感染阶段构成了浮游动物的重要组成部分，浮游动物是幼鱼和其他高等生物的基本食物来源。有趣的是，寄生虫也会相互影响，因为不同的物种可以竞争共同感染的软体动物宿主内的资源，因此一种寄生虫物种丰度的任何变化都可以对其竞争对手产生连锁反应。在吸虫中，血吸虫科是一个重要的科，其中血吸虫属值得注意，因为在低收入到中等收入国家(LMIC)，该属的物种对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，大规模的药物管理经常被用来控制寄生虫。这种大规模药物管理方案阻止或极大地减少软体动物感染阶段进入水环境的产出。这些大规模和反复的寄生虫扰动对水生食物网结构和/或功能的未知后果，将是本博士论文的重点。具体地说，我们的目标是确定：1)血吸虫在维多利亚湖的水生食物网中扮演什么角色。2)人类大规模用药在多大程度上改变了食物网的结构和营养动态。3)食物网内的任何扰动持续了多长时间。4)我们是否可以利用对食物网生态学中寄生虫的新理解来改善水生生态系统的健康，包括减少血吸虫的传播。

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.