Abstract：
Host species that can independently maintain a pathogen in a host community and contribute to infection in other species are important targets for disease management. However, the potential of host species to maintain a pathogen is not fixed over time, and an important challenge is understanding how within- and across-season variability in host maintenance potential affects pathogen persistence over longer time scales relevant for disease management (e.g., years). Here, we sought to understand the causes and consequences of seasonal infection dynamics in leopard frogs (Rana sphenocephala and Rana pipiens) infected with the fungal pathogen Batrachochytrium dendrobatidis (Bd). We addressed three questions broadly applicable to seasonal host-parasite systems. First, to what degree are observed seasonal patterns in infection driven by temperature-dependent infection processes compared to seasonal host demographic processes? Second, how does seasonal variation in maintenance potential affect long-term pathogen persistence in multi-host communities? Third, does high deterministic maintenance potential relate to the long-term stochastic persistence of pathogens in host populations with seasonal infection dynamics? To answer these questions, we used field data collected over 3 years on >1400 amphibians across four geographic locations, laboratory and mesocosm experiments, and a novel mathematical model. We found that the mechanisms that drive seasonal prevalence were different from those driving seasonal infection intensity. Seasonal variation in Bd prevalence was driven primarily by changes in host contact rates associated with breeding migrations to and from aquatic habitat. In contrast, seasonal changes in infection intensity were driven by temperature-induced changes in Bd growth rate. Using our model, we found that the maintenance potential of leopard frogs varied significantly throughout the year and that seasonal troughs in infection prevalence made it unlikely that leopard frogs were responsible for long-term Bd persistence in these seasonal amphibian communities, highlighting the importance of alternative pathogen reservoirs for Bd persistence. Our results have broad implications for management in seasonal host-pathogen systems, showing that seasonal changes in host and pathogen vital rates, rather than the depletion of susceptible hosts, can lead to troughs in pathogen prevalence and stochastic pathogen extirpation.
摘要：
能够在宿主群落中独立维持病原体并有助于其他物种感染的宿主物种是疾病管理的重要目标。然而,宿主物种维持病原体的潜力随着时间的推移并不固定，一个重要的挑战是了解宿主维持潜力的季节内和跨季节变化如何影响与疾病管理相关的更长时间尺度上的病原体持久性(例如，years).这里,我们试图了解感染真菌病原体Batrachochytriumdendrobatidis（Bd）的豹蛙（Ranasphenocphala和Ranapipiens）季节性感染动态的原因和后果。我们解决了三个广泛适用于季节性宿主-寄生虫系统的问题。首先,与季节性宿主人口统计过程相比，温度依赖性感染过程驱动的感染季节性模式在多大程度上观察到？第二，维持潜力的季节性变化如何影响多宿主社区的长期病原体持久性？第三，Dohighdeterminativemaintenancepotentialrelatedtothelong-termrandomentpersistenceofcasonalinfectiondynamics?Toanswerthesequestions,我们使用了3年来在四个地理位置收集的>1400个两栖动物的野外数据，实验室和中观实验，和一个新的数学模型。我们发现，驱动季节性流行的机制与驱动季节性感染强度的机制不同。Bd患病率的季节性变化主要是由与水生栖息地的繁殖迁移相关的宿主接触率的变化驱动的。相比之下,感染强度的季节性变化是由温度诱导的Bd生长速率变化驱动的。使用我们的模型，我们发现，豹蛙的维持潜力在一年中变化很大，并且感染流行率的季节性低谷使得豹蛙不太可能负责这些季节性两栖动物群落中的长期Bd持久性，强调替代病原体储库对Bd持久性的重要性。我们的结果对季节性宿主病原体系统的管理具有广泛的意义，显示宿主和病原体的发病率的季节性变化，而不是易感宿主的耗尽，可能导致病原体流行和随机病原体灭绝的低谷。
