Increases in the intensity and frequency of wildfires highlight the need to understand how fire disturbance affects ecological interactions. Though the effects of wildfire on free-living aquatic communities are relatively well-studied, how host–parasite interactions respond to fire disturbance is largely unexplored. Using a Before-After-Control-Impact design, we surveyed 10 stream sites (5 burned and 5 unburned) in the Willamette River Basin, Oregon and quantified snail host infection status and trematode parasite community structure 1 year before and two years after historic wildfires. Despite the severity of the wildfires, snail host populations did not show significant shifts in density or size distributions. We detected nine taxa of trematode parasites and overall probability of infection remained consistent over the three-year study period. However, at the taxon-specific level, we found evidence that infection probability by one trematode decreased and another increased after fire. In a larger dataset focusing on the first year after fire (9 burned, 8 unburned sites), we found evidence for subtle differences in trematode community structure, including higher Shannon diversity and evenness at the burned sites. Taken together, host–parasite interactions were remarkably stable for most taxa; for trematodes that did show responses, changes in abundance or behavior of definitive hosts may underlie observed patterns. These results have implications for using parasites as bioindicators of environmental change and suggest that aquatic snail-trematode interactions may be relatively resistant to wildfire disturbance in some ecosystems.

野火强度和频率的增加凸显了了解火灾干扰如何影响生态相互作用的必要性。尽管野火对自由生活的水生群落的影响已得到相对充分的研究，但宿主与寄生虫之间的相互作用如何应对火灾干扰很大程度上尚未被探索。采用前后控制影响设计，我们调查了俄勒冈州威拉米特河流域的 10 个溪流地点（5 个被烧毁，5 个未烧毁），并量化了历史性野火发生前 1 年和发生后两年的蜗牛宿主感染状况和吸虫寄生虫群落结构。尽管野火很严重，但蜗牛宿主种群的密度或大小分布并未出现显着变化。我们检测到了九个吸虫寄生虫类群，并且在三年的研究期间总体感染概率保持一致。然而，在特定分类水平上，我们发现有证据表明火灾后一种吸虫的感染概率下降，另一种吸虫的感染概率增加。在关注火灾后第一年（9 个烧毁地点、8 个未烧毁地点）的较大数据集中，我们发现了吸虫群落结构存在细微差异的证据，包括烧毁地点较高的香农多样性和均匀度。总的来说，对于大多数类群来说，宿主与寄生虫的相互作用非常稳定。对于确实表现出反应的吸虫，最终宿主的丰度或行为的变化可能是观察到的模式的基础。这些结果对于使用寄生虫作为环境变化的生物指示剂具有重要意义，并表明水生蜗牛与吸虫的相互作用可能对某些生态系统中的野火干扰具有相对抵抗力。