A framework for reconciling competing effects of competitors on disease transmission

生物多样性正在以惊人的速度消失，与此同时，传染病越来越多地从野生动物传染给人类。因此，迫切需要了解物种多样性如何影响野生动物的传染病。在某些生态系统中，竞争物种多样性的增加降低了疾病风险，这被称为“稀释”效应，因为多样性稀释了感染。然而，在其他系统中，更多样化的社区会增加疾病风险，称为“放大”效应。什么时候稀释或放大是疾病生态学家争论的话题。该项目旨在以鹿鼠中的Sin Nombre汉坦病毒（SNV）为模型，调和生物多样性的竞争效应。该系统同时显示稀释和扩增的各个方面。该项目为研究稀释和扩增的潜在机制以及它们如何相互作用以潜在地协同或拮抗提供了一个框架。这将有助于超越关于哪种模式（稀释或放大）更普遍的长期辩论，澄清何时不同的机制可能占主导地位，并有助于解释各种研究中看到的不同模式。它还将通过推进汉坦病毒肺综合征（HPS）的预防工作而造福社会。这种由SNV引起的人类疾病自1993年发现以来已影响了700多人（造成250多人死亡）。这项研究的其他更广泛的影响包括外展和与美洲原住民的合作，特别关注K-12外展。三种机制决定了竞争者多样性的增加是否会导致直接传播的病原体的稀释或扩增。如果物种多样性增加导致1）宿主密度降低，2）接触率降低，或3）给定接触的传播概率降低（可传播性），则会发生稀释。相反，如果增加多样性，则可能发生扩增。该项目开发了一个框架，以解开这些成分的稀释和放大效应，围绕一个数学模型，结合SIR（易感-感染-感染）动力学与Lotka-Volterra竞争系数。目的1是通过对纵向数据进行贝叶斯人口分析，确定增加的小型哺乳动物多样性/组成如何影响小鼠种群人口统计学和随后的SNV患病率。目的2是确定如何增加小型哺乳动物的多样性影响的传输率，通过改变传输率（通过压力，共感染，免疫力和病毒脱落）和/或鹿鼠之间的接触率，使用长期监测的生理在自然种群的组合，并在现场进行实验操作。目标3是将目标1和目标2的研究结果综合成一个通用模型，说明竞争对手如何对传播的所有三个组成部分产生不同的影响，并扩大规模，以确定系统内和系统间疾病流行的各种观察模式。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Biodiversity is disappearing at an alarming rate, and at the same time, infectious diseases increasingly spill over from wildlife to humans. Therefore, it is urgent to understand how species diversity affects infectious diseases in wildlife. In some ecosystems, increasing diversity of competitor species decreases disease risk, termed the 'dilution' effect because diversity dilutes out infection. However, in other systems, a more diverse community increases disease risk, termed the ‘amplification’ effect. When to expect dilution or amplification is a topic of debate among disease ecologists. This project aims to reconcile the competing effects of biodiversity using Sin Nombre hantavirus (SNV) in deer mice as a model. This system displays aspects of both dilution and amplification at the same time. This project lays out a framework for examining potential mechanisms of dilution and amplification and how they can interact to potentially be synergistic or antagonistic. This will facilitate moving beyond the long-standing debate of which pattern (dilution or amplification) is more prevalent, clarifying when different mechanisms may be dominant and help explain the different patterns seen in various studies. It will also benefit society by advancing prevention efforts for hantavirus pulmonary syndrome (HPS). This human illness caused by SNV, has affected more than 700 people (killing more than 250) since its discovery in 1993. Other broader Impacts of this research include outreach and work with Native Americans, with particular focus on K-12 outreach. Three mechanisms determine if increasing competitor diversity will lead to dilution or amplification of a directly transmitted pathogen. Dilution will occur if increased species diversity leads to 1) decreased host density, 2) decreased contact rates, or 3) decreased probability of transmission given contact (transmissibility). Conversely, amplification could occur if increased diversity does the opposite. This project develops a framework to disentangle these component dilution and amplification effects, centered around a mathematical model that combines SIR (Susceptible-Infected-Recovered) dynamics with a Lotka-Volterra competition coefficient. Aim 1 is to determine how increased small mammal diversity / composition affects mouse population demography and subsequent SNV prevalence, by performing Bayesian population analyses on longitudinal data. Aim 2 is to determine how increased small mammal diversity affects the transmission rate, through changes in transmissibility (via stress, co-infections, immunity, and viral shedding) and/or contact rates between deer mice, using a combination of long-term monitoring of physiology in natural populations, and experimental manipulation in the field. Aim 3 is to synthesize the findings from Aims 1 and 2 into a general model of how competitors can differentially affect all three components of transmission and scale up to determine the variety of observed patterns in disease prevalence within and across systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.