Pythium insidiosum is a widespread pathogen that causes pythiosis in mammals. Recent increase in cases reported in North America indicates a need to better understand the distribution and persistence of the pathogen in the environment. In this study, we reconstructed the distribution of P. insidiosum in the Chincoteague National Wildlife Refuge, located on Assateague Island, Virginia, and based on 136 environmental water samples collected between June and September of 2019. The Refuge hosts two grazing areas for horses, also known as the Chincoteague Ponies. In the past 3 years, 12 horses have succumbed to infection by P. insidiosum. Using an ecological niche model framework, we estimated and mapped suitable areas for P. insidiosum throughout the Refuge. We found P. insidiosum throughout much of the study area. Our results showed significant monthly variation in the predicted suitability, where the most influential environmental predictors were land-surface water and temperature. We found that June, July, and August were the months with the highest suitability for P. insidiosum across the Refuge, while December through March were less favorable months. Likewise, significant differences in suitability were observed between the two grazing areas. The suitability map provided here could also be used to make management decisions, such as monitoring horses for lesions during high risk months.

腐霉是一种广泛传播的病原体，可引起哺乳动物的腐霉病。最近北美报告的病例增加表明需要更好地了解病原体在环境中的分布和持久性。在这项研究中，我们重建了P. insidiosum位于弗吉尼亚州阿萨蒂格岛的钦科蒂格国家野生动物保护区，基于 2019 年 6 月至 9 月期间收集的 136 个环境水样。保护区有两个马匹放牧区，也称为钦科蒂格小马。在过去的 3 年里，有 12 匹马死于感染P. insidiosum. 使用生态位模型框架，我们估计并绘制了合适的区域P. insidiosum整个避难所。我们发现P. insidiosum遍及大部分研究区域。我们的结果显示，预测适宜性的月度变化显着，其中最具影响力的环境预测因子是地表水和温度。我们发现 6 月、7 月和 8 月是最适合P. insidiosum整个避难所，而 12 月到 3 月是不太有利的月份。同样，在两个放牧区之间观察到适宜性的显着差异。此处提供的适用性图还可用于做出管理决策，例如在高风险月份监测马匹的病变。