Are all hosts created equal? Transmission dynamics in a natural multi-host parasite community

许多关于人类（如大流行性流感，西尼罗河病毒，汉坦病毒）和野生动物（如牛和獾的牛结核病，从灰松鼠到红松鼠的松鼠痘传播）中新出现的传染病的最紧迫的担忧来自寄生虫从一个宿主物种转移到另一个宿主物种。因此，人们对一个社区中可能的宿主的组成如何影响疾病是否传播非常感兴趣。每个宿主物种对寄生虫的易感性、社会结构和/或行为都不同，因此宿主群落的组成在决定为什么一些寄生虫会引起流行病（如艾滋病毒）而另一些寄生虫不会引起流行病（如埃博拉病毒）方面起着关键作用。为了帮助我们了解这些复杂的现实世界的社区，已经开发了几个数学模型，这些模型表明，每个宿主物种对寄生虫传播能力的贡献对于确定疾病是否持续以及目标控制的结果至关重要。然而，到目前为止，这些理论还没有经过实际数据的检验，这意味着它们在很大程度上仍然是抽象的概念框架。特别是，不知道宿主物种对疾病传播的贡献是否可以仅从每个宿主物种内受感染个体的数量来确定。这一点很重要，因为大多数关于感染多个宿主的寄生虫的研究可能纯粹是观察性的，因为进行必要的实验在逻辑上或伦理上是不可行的。然而，可能有一般的指导方针，根据宿主-寄生虫生态学的基本方面，可以用来推断这些主机的贡献寄生虫的传播和持久性。例如，寄生虫的传播生物学（即它如何从一个宿主转移到另一个宿主）和宿主物种在群落中相互作用的方式（例如它们的移动模式，栖息地使用，资源竞争等）将决定每个宿主物种如何促进寄生虫的持续存在。显然，有必要确定我们在自然界中看到的疾病模式，结合对宿主-寄生虫生物学的基本理解，是否可以用来预测寄生虫将如何对针对一个或另一个宿主物种的控制措施作出反应。我们将使用一个非常新颖的组合，大规模的操作实验和数学建模来衡量宿主物种的贡献，寄生虫传播在一个多样化的，自然的多宿主多寄生虫社区。总的来说，我们将提供一个最全面的观点，非常不同的寄生虫，不同的传播模式，使用多个宿主物种坚持，以及这些寄生虫如何响应有针对性的宿主治疗的影响。鉴于对地球仪新出现的传染病的日益关注，对影响寄生虫入侵、传播、持久性和控制的因素的真正理解从未像现在这样紧迫。该项目将是朝着这一方向迈出的重要一步。

Many of the most pressing concerns about emerging infectious disease in humans (eg pandemic influenza, West Nile virus, Hantavirus) and wildlife (eg bovine TB in cattle and badgers, squirrel pox transmission from grey to red squirrels) arise from parasites moving from one host species to another. As such there is considerable interest in how the composition of possible hosts in a community affects whether a disease spreads or not. Each host species can differ in their susceptibility to the parasite, their social structure and/or behaviour, so that the composition of the host community plays a key role in determining why some parasites cause an epidemic (i.e HIV), while others don't (i.e. Ebola). To aid our understanding of these complex, real-world communities, several mathematical models have been developed which show that the contribution each host species makes to the parasite's ability to spread is fundamental in determining whether the disease persists, and the outcome of targeted control. To date, however, these theories have not been tested with actual data, meaning they largely remain abstract conceptual frameworks. In particular, it is not known whether the host species' contributions to disease spread can be determined solely from the number of infected individuals within each host species. This is important as most studies of parasites that infect multiple hosts are likely to be purely observational, because it is logistically or ethically unfeasible to conduct the necessary experiments. However, there may be general guidelines, based on fundamental aspects of host-parasite ecology that can be used to infer these host contributions to parasite transmission and persistence. For example, both the transmission biology of the parasite (ie how it moves from one host to another) and the way host species interact in the community (eg their movement patterns, habitat usage, resource competition etc) will determine how each host species contributes to parasite persistence. Clearly, there is a need to determine whether disease patterns that we see in nature, combined with a basic understanding of host-parasite biology, can be used to predict how parasites will respond to control efforts targeting one host species or another. We will use a highly novel combination of large-scale manipulation experiments and mathematical modelling to measure host species contributions to parasite transmission across a diverse, natural multi-host-multi-parasite community. Overall we will provide one of the most comprehensive views of how very different parasites, with different transmission modes, use multiple host species to persist, and the implications for how such parasites respond to targeted host treatment. Given the increasing concerns about emerging infectious diseases around the globe, it has never been more pressing to develop a genuine understanding of the factors affecting parasite invasion, transmission, persistence, and control. This project will be a major step in that direction.