Global climate change is altering the abundance and spread of various parasites, which has important consequences not only for host–parasite interactions but also for the relationships between different host species. Here, we focus on the myxozoan endoparasite Tetracapsuloides bryosalmonae that causes temperature‐dependent proliferative kidney disease (PKD) in salmonids. We characterized the temporal changes in the parasite load and the severity of PKD signs (renal hyperplasia, haematocrit) in two sympatric populations of wild brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). We found that both the parasite load and disease signs vary considerably between individuals, species, rivers and sampling periods. We showed that Atlantic salmon was able to slow down the initial parasite proliferation rate and subsequently tolerate high parasite burden without obvious disease signs. In contrast, the initial parasite proliferation rate was much higher in brown trout, which was followed by the development of severe PKD signs. Thus, the speed of parasite proliferation, rather than the absolute number of the parasites in the host kidney, may play an important role in interspecific variation in PKD susceptibility. To conclude, this study illustrates the usefulness of temporal perspective for understanding host defence mechanisms and climate change‐mediated impacts in the wild.

中文翻译：

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同伴宿主中的气候变化驱动疾病：野生褐鳟鱼和大西洋鲑鱼的寄生虫负担和增生性肾脏疾病的时空动态

全球气候变化正在改变各种寄生虫的丰度和传播，这不仅对寄主－寄生虫的相互作用而且对不同寄主物种之间的关系都具有重要的影响。在此，我们重点研究引起鲑鱼类依赖温度的增生性肾脏疾病（PKD）的粘液虫内寄生虫四囊线虫。我们表征了野生棕鳟鱼（Salmo trutta）和大西洋鲑鱼（Salmo salar）的两个同伴种群中的寄生虫负荷和PKD迹象严重程度（肾脏增生，血细胞比容）的时空变化。）。我们发现，在个体，物种，河流和采样期之间，寄生虫的负荷和疾病迹象均存在很大差异。我们表明大西洋鲑鱼能够减慢初始寄生虫的增殖速度，并随后忍受较高的寄生虫负担，而没有明显的疾病迹象。相比之下，褐鳟的初始寄生虫增殖率要高得多，然后是严重的PKD征兆。因此，寄生虫增殖的速度，而不是宿主肾脏中寄生虫的绝对数目，可能在PKD敏感性的种间变异中起重要作用。总而言之，这项研究说明了时空观点对于理解宿主防御机制和气候变化介导的野外影响的有用性。