COLLABORATIVE RESEARCH: Evolution of virulence in a host-pathogen system

该项目将提高我们对传染病系统演变的了解，同时也有助于教育和制定保护两栖动物多样性的保护战略。疾病流行很少以宿主种群完全灭绝而告终。特别是在高致命性疾病中，理论预测将从爆发阶段转移到爆发后阶段，在那里宿主和病原体持续存在于共同的环境中。疾病状态的这种转变提供了一个移动的目标，限制了成功干预战略的发展。这项研究通过重点研究有记录以来最具破坏性的脊椎动物传染病之一--两栖融合菌病，来调查推动疾病动力学进化转变的因素。棘霉病是由一种真菌病原体引起的，这种病原体可以在两栖动物种群中迅速传播，并导致极高的死亡率，这表明它是一种强烈的自然选择因素。这种疾病已经造成--并将继续造成--世界各地两栖动物生物多样性的急剧丧失。研究人员正在利用对棘球菌病的深入了解来制定以科学为基础的保护策略。这项研究与教育宣传相结合，包括以一年一度的国际拯救青蛙日为中心的公共研讨会和演讲。这项研究利用了中美洲十年的研究成果，以及史无前例的疾病数据、病原体分离和宿主样本档案。病原体分离和宿主样本是在疾病暴发阶段收集和存档的，在八至十年后开始的流行阶段也在收集类似的数据。研究人员正在使用实验和分子方法来研究这样的假设：(1)自最初的疫情爆发以来，病原体的毒力水平发生了变化，(2)宿主已经进化到对感染更耐受。为了验证这些假设，研究人员正在测试历史和当代样本，以确定与病原体毒力和宿主免疫防御有关的表型和遗传差异。这些结果将为保护两栖动物生物多样性和理解进化在形成新出现的传染病流行后动态中的作用提供见解。

This project will improve our understanding of the evolution of infectious disease systems while also contributing to education and the development of conservation strategies for protecting amphibian diversity. Disease epidemics rarely end in the complete extinction of host populations. Especially in highly lethal diseases, theory predicts a shift away from the outbreak phase to a post-outbreak stage where hosts and pathogens persist in a shared environment. Such transitions in disease states present a moving target that limits the development of successful intervention strategies. This research investigates the factors that drive evolutionary shifts in disease dynamics by focusing on one of the most devastating infectious diseases of vertebrates in recorded history, amphibian chytridiomycosis. Chytridiomycosis is caused by a fungal pathogen that can spread rapidly through amphibian populations and cause extremely high levels of mortality, suggesting that it is a strong agent of natural selection. This disease has caused - and continues to cause - dramatic losses of amphibian biodiversity around the world. The investigators are using an in-depth understanding of chytridiomycosis to develop science-based conservation strategies. The research is integrated with educational outreach, including public workshops and presentations centered on the annual International Save the Frogs Day. This research capitalizes on a decade of research in Central America and on an unprecedented archive of disease data, pathogen isolates, and host samples. Pathogen isolates and host samples were collected and archived during the outbreak phase of the disease and similar data are being collected during the endemic phase, beginning eight to ten years later. The researchers are using experimental and molecular methods to investigate the hypotheses that (1) the level of pathogen virulence has shifted since the original outbreaks and (2) that hosts have evolved to be more tolerant of infection. To test these hypotheses, the investigators are testing the historic and contemporary samples to identify phenotypic and genetic differences linked to pathogen virulence host immune defenses. The results will provide insights for safeguarding amphibian biodiversity and for understanding the role of evolution in shaping post-epidemic dynamics of emerging infectious diseases.