Abstract The ubiquitous freshwater pathogen Saprolegnia parasitica has long been considered a true generalist, capable of infecting a wide range of fish species. It remains unclear, however, whether different isolates of this pathogen, obtained from distinct geographic locations and host species, display differences in host preference. To assess this, the current study examined the induced zoospore encystment responses of four S. parasitica isolates towards the skin of four fish species. While three of the isolates displayed ‘specialist’ responses, one appeared to be more of a ‘generalist’. In vivo challenge infections involving salmon and sea trout with the ‘generalist’ (salmon isolate EA001) and a ‘specialist’ (sea trout isolate EA016) pathogen, however, did not support the in vitro findings, with no apparent host preference reflected in infection outcomes. Survival of sea trout and salmon though was significantly different following a challenge infection with the sea trout (EA016) isolate. These results indicate that while S. parasitica isolates can be considered true generalists, they may target hosts to which they have been more frequently exposed (potential local adaptation). Understanding host preference of this pathogen could aid our understanding of infection epidemics and help with the development of fish management procedures.

中文翻译：

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寄生水霉游动孢子活性和宿主存活表明宿主偏好的分离变异

摘要 普遍存在的淡水病原体寄生水霉长期以来一直被认为是真正的通才，能够感染多种鱼类。然而，从不同的地理位置和宿主物种获得的这种病原体的不同分离物是否表现出宿主偏好的差异仍不清楚。为了评估这一点，目前的研究检查了四种寄生虫分离株对四种鱼类皮肤的诱导游动孢子包囊反应。虽然其中三个分离株表现出“专家”的反应，但一个似乎更像是“通才”。然而，体内挑战感染涉及鲑鱼和海鳟的“通才”（鲑鱼分离株 EA001）和“专家”（海鳟分离株 EA016）病原体，但不支持体外研究结果，感染结果中没有反映明显的宿主偏好。在海鳟（EA016）分离株攻击感染后，海鳟和鲑鱼的存活率显着不同。这些结果表明，虽然 S. parasitica 分离株可以被认为是真正的通才，但它们可能针对它们更频繁接触的宿主（潜在的局部适应）。了解这种病原体的宿主偏好可以帮助我们了解感染流行病，并有助于制定鱼类管理程序。它们可能针对它们更频繁接触的宿主（潜在的局部适应）。了解这种病原体的宿主偏好可以帮助我们了解感染流行病，并有助于制定鱼类管理程序。它们可能针对它们更频繁接触的宿主（潜在的局部适应）。了解这种病原体的宿主偏好可以帮助我们了解感染流行病，并有助于制定鱼类管理程序。