Many pathogens interact and evolve in communities where more than one host species is present, yet our understanding of host–pathogen specialization is mostly informed by laboratory studies with single species. Managing diseases in the wild, however, requires understanding how host–pathogen specialization affects hosts in diverse communities. Juvenile salmonid mortality in hatcheries caused by infectious hematopoietic necrosis virus (IHNV) has important implications for salmonid conservation programs. Here, we evaluate evidence for IHNV specialization on three salmonid hosts and assess how this influences intra‐ and interspecific transmission in hatchery‐reared salmonids. We expect that while more generalist viral lineages should pose an equal risk of infection across host types, viral specialization will increase intraspecific transmission. We used Bayesian models and data from 24 hatcheries in the Columbia River Basin to reconstruct the exposure history of hatcheries with two IHNV lineages, MD and UC, allowing us to estimate the probability of juvenile infection with these lineages in three salmonid host types. Our results show that lineage MD is specialized on steelhead trout and perhaps rainbow trout (both Oncorhynchus mykiss), whereas lineage UC displayed a generalist phenotype across steelhead trout, rainbow trout, and Chinook salmon. Furthermore, our results suggest the presence of specialist–generalist trade‐offs because, while lineage UC had moderate probabilities of infection across host types, lineage MD had a small probability of infection in its nonadapted host type, Chinook salmon. Thus, in addition to quantifying probabilities of infection of socially and economically important salmonid hosts with different IHNV lineages, our results provide insights into the trade‐offs that viral lineages incur in multihost communities. Our results suggest that knowledge of the specialist/generalist strategies of circulating viral lineages could be useful in salmonid conservation programs to control disease.

中文翻译：

---

传染性造血坏死病毒专门存在于多宿主鲑鱼系统中。

许多病原体在存在不止一种宿主物种的群落中相互作用和进化，但我们对宿主-病原体专业化的理解主要是通过对单一物种的实验室研究来了解的。然而，在野外管理疾病需要了解宿主-病原体的专门化如何影响不同社区的宿主。传染性造血坏死病毒 (IHNV) 引起的孵化场幼鱼死亡率对鲑鱼保护计划具有重要意义。在这里，我们评估了 IHNV 对三种鲑鱼宿主的专门化证据，并评估了这如何影响孵化场养殖的鲑鱼的种内和种间传播。我们预计，虽然更通用的病毒谱系应该在不同宿主类型之间造成相同的感染风险，但病毒的特化将增加种内传播。我们使用贝叶斯模型和来自哥伦比亚河流域 24 个孵化场的数据重建了具有两个 IHNV 谱系（MD 和 UC）的孵化场的暴露历史，使我们能够估计幼鱼在三种鲑鱼宿主类型中感染这些谱系的概率。我们的结果表明，谱系MD专门针对硬头鳟鱼，也许还有虹鳟鱼（均为Oncorhynchus mykiss），而谱系UC则在虹鳟鱼、虹鳟鱼和奇努克鲑鱼中表现出通用表型。此外，我们的结果表明存在专家与通才的权衡，因为虽然谱系 UC 在不同宿主类型中具有中等的感染概率，但谱系 MD 在其非适应宿主类型奇努克鲑鱼中的感染概率较小。因此，除了量化具有不同 IHNV 谱系的具有社会和经济重要性的鲑鱼宿主的感染概率之外，我们的结果还提供了对病毒谱系在多宿主群落中发生的权衡的见解。我们的结果表明，关于循环病毒谱系的专业/通才策略的知识可能有助于鲑鱼保护计划以控制疾病。