Quantifying host species contributions to pathogen transmission in a multihost community: the case of chytrid fungus in amphibian communities

许多引起全球健康和保护关注的病原体感染多个寄主物种。埃博拉就是一个典型的例子，它在“宿主”群体中自然传播，并有可能传播到另一个宿主物种，造成毁灭性的影响。显然，了解这些病原体在它们的宿主群落中是如何维持的，以及哪些物种在传播这些病原体方面发挥了主要作用，这一点至关重要。然而，要获得这种理解是出了名的难。我们最近开发了一种数学方法来衡量宿主群落维持病原体的能力，并确定推动病原体传播的“关键宿主”。重要的是，与以前的方法不同，这种方法可以使用相对粗粒度的、容易收集的数据(宿主丰度和感染发生的标准衡量标准)进行参数化。我们将对这一模型进行第一次严格的测试，将其应用于一个自然的多宿主病原体系统，这是一个主要的保护问题：两栖动物群落中的壶菌(‘Bd’)。BD是全球两栖动物数量下降的主要原因，但我们不知道它是如何通过两栖动物群落传播或由其维持的。我们将对历史数据和新数据应用我们的数学方法，并使用它来识别这些关键主机，并预测删除它们的影响。至关重要的是，我们将通过进行物种清除实验来直接检验这些预测。总体而言，这将为我们的数学工具提供一个严格的测试，显示宿主群落如何影响病原体传播，并为BD的管理提供具体的指导方针。

Many pathogens of global health and conservation concern infect multiple host species. Ebola is a classic example, circulating naturally within a 'reservoir' host community, and with the potential to jump across to another host species with devastating effect. Clearly it is vital to understand how such pathogens are maintained in their host communities, and which species play a major role in spreading those pathogens. However, obtaining that understanding is notoriously hard. We have recently developed a mathematical approach to measure a host community's ability to maintain a pathogen, and identify 'key hosts' that drive pathogen spread. Importantly, unlike previous methods, this approach can be parameterised using relatively coarse-grained, easily-collected data (standard measures of host abundance and infection occurrence). We will provide the first rigorous test of this model, applying it to a natural 'multihost'-pathogen system of major conservation concern: chytrid fungus ('Bd') in amphibian communities. Bd is a major cause of amphibian declines worldwide, but we don't understand how it spreads through or is maintained by amphibian communities. We will apply our mathematical approach to historical and new data, and use it to identify those key hosts, and predict the effect of removing them. Crucially, we will then directly test those predictions by carrying out species removal experiments. Overall this will provide a rigorous test of our mathematical tool, show how host communities affect pathogen spread in general, and provide specific guidelines for the management of Bd in particular.