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理解，同时也有助于教育和保护两栖动物多样性的保护战略的发展。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，理论预测会从爆发阶段转移到爆发后阶段，宿主和病原体在共同的环境中持续存在。疾病状态的这种转变提出了一个移动的目标，限制了成功的干预策略的发展。本研究通过关注有记录历史上最具破坏性的脊椎动物传染病之一两栖动物壶菌病，调查了推动疾病动力学进化转变的因素。壶菌病是由一种真菌病原体引起的，这种真菌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，这表明它是自然选择的一个强大因素。这种疾病已经并将继续导致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壶菌病的深入了解来制定以科学为基础的保护策略。该研究与教育推广相结合，包括以年度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和前所未有的疾病数据、病原体分离株和宿主样本档案。在疾病爆发阶段收集了病原体分离株和宿主样本并存档，在8至10年后开始的地方流行阶段收集了类似的数据。研究人员正在使用实验和分子方法来研究以下假设：（1）病原体毒力水平自最初爆发以来发生了变化，（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宿主免疫防御相关的表型和遗传差异。研究结果将为保护两栖动物生物多样性和理解进化在塑造新出现的传染病的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.