Testing Mechanistic Models to Explain How Variation in Host Susceptibility Arises and Why It Shifts Across Thermal Gradients.

气候变化导致的环境条件变化有可能改变现有的生态相互作用，包括病原体和宿主之间的动态。因此，深入了解驱动宿主-病原体动力学的机制以及环境条件对这些机制的影响对于预测和准备未来环境变化的影响至关重要。这项工作测试了关于温度影响太平洋鲱鱼（一种生态和经济上重要的海洋饲料鱼）病原体敏感性的一般机制的新假设。通过将数学模型拟合到实验室和实地收集的数据来检验假设，这些数据评估了鲱鱼和适应冷水和温水的病原体在不同温度梯度下的反应。这项工作产生的基础信息提高了预测能力，以评估气候变化对宿主-病原体相互作用长期稳定性的影响，并在基本进化过程和疾病生态学之间建立联系。此外，研究结果使渔业管理者了解水温升高对鲱鱼动物流行病的影响；因此，可以在鲱鱼种群评估模型中更细致地使用疾病信息，并有助于可持续的水生资源管理。除了与渔业相关的研究外，更广泛的影响集中在创建和评估多语言宣传材料上，这些材料可以教育高中和大学学生了解气候和疾病如何相互作用影响农业和野生动物物种。研究人员还在开发一个简单的交互式网络应用程序，供管理人员探索该模型。宿主人群的易感性分布决定了短期和长期的流行病特征。然而，对产生易感性变化的机制知之甚少，目前的理论认为易感性的分布在不同的环境条件下是固定的。因此，我们了解和预测气候变化下流行病后果的能力是有限的。本提案的中心假设试图通过假设病原体敏感性的变化是由宿主和病原体在给定温度条件下的相对表现所定义的随机过程来验证这一假设。或者，易感性的变异可以用宿主易感性热反应规范的遗传变异来解释。使用太平洋鲱鱼适应温水和冷水的病原体对这些假设进行了测试，并将涉及使用数学模型将宿主内感染动态与宿主间传播动态联系起来。根据从实验室和实地动物流行病实验中获得的实验数据，正在进一步审查已发展的理论。通过对收集到的数据进行严格的理论测试，该项目提供了对产生疾病易感性变化的一般机制的见解，并量化了热梯度在形成易感性分布中所起的作用。因此，该项目有可能提供新的方法来评估气候变化对宿主-病原体相互作用长期稳定性的影响。此外，通过描述易感性分布与温度之间的相互作用，该项目确定了可能成为气候变化下疾病缓解重点的基本机制过程。这个传染病生态学和进化项目是由生物海洋学计划和促进竞争性研究的既定计划（EPSCoR）共同资助的。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

Shifting environmental conditions resulting from climate change have the potential to alter established ecological interactions, including the dynamics between pathogens and hosts. As a result, developing a thorough understanding of both the mechanisms that drive host-pathogen dynamics and the influence of environmental conditions on these mechanisms is of paramount importance to predicting and preparing for the effects of future environmental change. This work tests novel hypotheses about the general mechanisms by which temperature influences pathogen susceptibility in Pacific herring, an ecologically and economically important marine forage fish. Hypotheses are being tested by fitting mathematical models to laboratory and field-collected data that evaluate the responses of herring and cold- and warm-water adapted pathogens across thermal gradients. The foundational information resulting from this work increases predictive capacities to assess the effects of a changing climate on the long-term stability of host-pathogen interactions and to build links between fundamental evolutionary processes and disease ecology. Further, results inform fisheries managers about impacts of increased water temperatures on herring epizootics; thereby allowing for a more nuanced use of disease information in herring stock assessment models and contributing to sustainable aquatic resource management. Beyond the study’s relevance to fisheries, the broader impacts focus on creating and evaluating multi-lingual outreach materials that educate high school and university students on how climate and disease interact to affect agricultural and wildlife species. The investigators are also developing a simple, interactive web application for managers to explore the model.The distribution of susceptibility in a host population determines short- and long-term epidemic characteristics. However, little is known about the mechanisms that generate variation in susceptibility, and current theory assumes that the distribution of susceptibility is fixed across environmental conditions. Our capacity to understand and predict epidemic outcomes under climate change is therefore limited. The central hypothesis of this proposal seeks to test this assumption by positing that the variation in pathogen susceptibility arises as a stochastic process defined by the relative performance of host and pathogen traits under a given temperature condition. Alternatively, variation in susceptibility may be explained by genetic variation in the thermal reaction norms of host susceptibility. These hypotheses are tested using warm- and cold-water adapted pathogens in Pacific herring and will involve the use of mathematical models to link the within-host infection dynamics to among-host transmission dynamics. Developed theory is being further scrutinized against experimental data obtained from laboratory and field epizootic experiments. By rigorously testing theory against collected data, this project provides insights into general mechanisms that generate variation in disease susceptibility and quantifies the roles that thermal gradients play in shaping susceptibility distributions. As a result, this project has the potential to provide new approaches to assess the consequences of a changing climate on the long-term stability of host-pathogen interactions. Furthermore, by describing the interplay between the distribution of susceptibility and temperature, this project identifies basic mechanistic processes that could be the foci of disease mitigation under climate change.This Ecology and Evolution of Infectious Diseases project is jointly funded by the Biological Oceanography Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.