Collaborative Research: After the Crash: Factors Allowing Host Persistence Following Outbreaks of a Highly Virulent Disease

壶菌病是一种由真菌病原体树枝状芽孢杆菌（Batrachochytrium dendrobatium，“Bd”）引起的两栖动物的新兴传染病，其被认为是世界各地两栖动物种群下降和灭绝的主要原因。 以目前全球Bd传播的快速速度，许多两栖动物种群将在未来十年内受到感染，这可能会导致这一已经濒危的生物群体中大量物种灭绝。 在加州的塞拉内华达州山区，Bd正在以前未感染的两栖动物种群中迅速传播。 山地黄腿蛙（Rana muscosa）对壶菌病高度敏感，并且由于Bd感染而经历了数百次最近的种群灭绝。 有趣的是，尽管大多数宿主种群在Bd到来后被灭绝，但一小部分种群仍与病原体共存，这些持久种群中的疾病动态与种群崩溃期间的疾病动态有着根本的不同。加州大学的研究人员进行这项研究的目的是了解导致这些截然不同的疾病结果的机制。 研究人员假设，种群灭绝与持久性是种群间差异的结果，这些差异包括（1）密度依赖性疾病动力学，（2）Bd毒力，（3）青蛙易感性或（4）环境条件。建立了R. muscosa-Bd相互作用，包括在主机内Bd动态和主机阶段结构将被参数化和测试。 此外，四个非互斥的假设，可以解释不同的疾病结果将使用现场和实验室实验进行测试。一个功能基因组学的方法，利用完整的Bd和青蛙基因组序列将被用来描述任何观察到的Bd毒力和/或青蛙易感性的差异的遗传基础。拟议的研究将大大有助于预测未来疾病对野生动物和人类的影响。就更广泛的影响而言，研究结果将直接关系到全球受疾病威胁的两栖动物的保护，并可能被广泛用于为保护战略和政策举措提供信息。 为确保迅速将成果纳入这些努力，将通过以下方式向决策者通报成果：（i）项目研究人员继续参与R. muscosa恢复工作组，（ii）与联邦和州负责R. Muscosa保护（例如，美国国家公园管理局。S.鱼类和野生动物服务，加州渔业和游戏部），和（iii）与非政府组织的协商，制定世界各地的两栖动物保护计划。该项目将通过直接参与研究，促进建模，基因组学，分子遗传学，统计学以及实验室和现场方法方面的各种学生和博士后研究人员的教学和培训。为了向更广泛的受众提供针对生物多样性的培训，将在项目期间与两栖动物专家组（IUCN，世界保护联盟）合作举办三个针对联邦和州机构生物学家和私人顾问的讲习班。还将以英文和西班牙文在线提供采样协议（文本和视频格式）。

Chytridiomycosis is an emerging infectious disease of amphibians caused by the fungal pathogen, Batrachochytrium dendrobatidis ("Bd") that has been implicated as a major cause of amphibian population declines and extinctions around the world. At the current rapid rate of global Bd spread, many amphibian populations will become infected within the next decade, and this will likely result in substantial numbers of species extinctions in this already-imperiled group of organisms. In California's Sierra Nevada mountains, Bd is rapidly spreading through previously uninfected amphibian populations. The mountain yellow-legged frog (Rana muscosa) is highly susceptible to chytridiomycosis, and has experienced hundreds of recent population extinctions due to Bd infection. Interestingly, although the majority of host populations are driven extinct following the arrival of Bd, a small fraction of populations persist with the pathogen, and disease dynamics in these persistent populations are fundamentally different from those during population crashes. The goal of this research by researchers from University of California is to understand the mechanisms leading to these contrasting disease outcomes. The investigators hypothesize that population extinction versus persistence is the result of between-population differences in (1) density-dependent disease dynamics, (2) Bd virulence, (3) frog susceptibility, or (4) environmental conditions. A model of the R. muscosa- Bd interaction that includes within-host Bd dynamics and host stage-structure will be parameterized and tested. In addition, four non-mutually exclusive hypotheses that could account for different disease outcomes will be tested using field and laboratory experiments. A functional genomics approach that utilizes complete Bd and frog genome sequences will be used to describe the genetic basis of any observed differences in Bd virulence and/or frog susceptibility. The proposed research will contribute significantly to the ability to predict outcomes of future diseases on wildlife and human populations. In terms of broader impacts, results from the research will be directly relevant to the conservation of amphibians worldwide that are threatened by disease, and will likely be broadly used to inform conservation strategies and policy initiatives. To ensure the rapid incorporation of results into such efforts, results will be communicated to policy makers via (i) continued participation by project researchers in an R. muscosa recovery working group, (ii) annual meetings with federal and state agencies charged with R. muscosa conservation (e.g., National Park Service, U. S. Fish and Wildlife Service, California Department of Fish and Game), and (iii) consultation with non-governmental organizations developing amphibian conservation programs worldwide. The project will promote teaching and training of a diverse group of students and postdoctoral researchers in modeling, genomics, molecular genetics, statistics, and laboratory and field methods through their direct involvement in the research. To provide Bd-specific training to a wider audience, three workshops targeted at federal and state agency biologists and private consultants will be hosted during the project in collaboration with the Amphibian Specialist Group (IUCN, World Conservation Union). Sampling protocols (in text and video formats) will also be provided online in both English and Spanish.