Ingestion of infected prey is the most recognizable mode of transmission for Ichthyophonus, but because this mode of transmission is unidirectional, from small prey to larger predators, it cannot sustain the parasite within or among populations, nor does it explain transmission to planktivores. Recently, water-born transmission was demonstrated in cultured rainbow trout Oncorhynchus mykiss, which could explain how the parasite is transmitted without piscivory. It is possible however, that this is an adaptation to culture conditions, and may not occur among wild fish. To address this question, experiments were conducted with the objectives of determining if a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species, as well as if transmission is possible between different marine species. Pacific staghorn sculpins Leptocottus armatus, were fed a freshwater isolate of Ichthyophonus (clade C) and then housed with susceptible sentinel Southern Rock sole Lepidopsetta bilineata. Ninety-two percent of the orally exposed sculpins and 30% of the sentinel sole were Ichthyophonus-positive at the end of the study, with 0% infected controls. These results demonstrate that a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species and can be transmitted in seawater in the absence of piscivory. It also provides a plausible mechanism for transmission to small prey fish and planktivores, as well as within a population of piscivores when infected prey is not available.

中文翻译：

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将鱼鱼淡水分离株（进化枝 C）传播给两种海洋鱼类

摄入受感染的猎物是鱼鱼最容易识别的传播方式，但由于这种传播方式是单向的，从小型猎物到大型捕食者，它不能在种群内或种群间维持寄生虫，也不能解释向浮游动物的传播。最近，在养殖的虹鳟鱼 Oncorhynchus mykiss 中证明了水生传播，这可以解释寄生虫如何在没有食鱼的情况下传播。然而，这可能是对养殖条件的一种适应，在野生鱼类中可能不会发生。为了解决这个问题，进行了一些实验，目的是确定淡水鱼属分离物是否对海洋物种具有传染性和致病性，以及是否可能在不同海洋物种之间传播。太平洋鹿角杜鹃 Leptocottus armatus 被喂食了淡水分离物 Ichthyophonus（进化枝 C），然后与易感的南方岩鲆 Lepidopsetta bilineata 一起饲养。在研究结束时，92% 的经口暴露的杜鹃和 30% 的哨兵鱼属鱼属阳性，0% 的对照被感染。这些结果表明，淡水鱼分离物对海洋物种具有传染性和致病性，并且可以在没有食鱼的情况下在海水中传播。它还提供了一种可能的机制，用于传播给小型猎物鱼类和浮游动物，以及在无法获得受感染猎物时在鱼类种群中传播。在研究结束时，92% 的经口暴露的杜鹃和 30% 的哨兵鱼属鱼属阳性，0% 的对照被感染。这些结果表明，淡水鱼分离物对海洋物种具有传染性和致病性，并且可以在没有食鱼的情况下在海水中传播。它还提供了一种可能的机制，用于传播给小型猎物鱼类和浮游动物，以及在无法获得受感染猎物时在鱼类种群中传播。在研究结束时，92% 的经口暴露的杜鹃和 30% 的哨兵鱼属鱼属阳性，0% 的对照被感染。这些结果表明，淡水鱼分离物对海洋物种具有传染性和致病性，并且可以在没有食鱼的情况下在海水中传播。它还提供了一种可能的机制，用于传播给小型猎物鱼类和浮游动物，以及在无法获得受感染猎物时在鱼类种群中传播。