Canadian Journal of Fisheries and Aquatic Sciences, Ahead of Print.
We provide the first documented case of whirling disease (WD) impacts to wild, self-sustaining rainbow trout (RNTR, Oncorynchus mykiss) populations in Canada. Myxobolus cerebralis (Mc), the causative agent of WD, was first confirmed in Alberta in 2016. However, evidence of disease in local fish populations was unknown. Using a weight-of-evidence approach, we examined multiple parasite life cycle stages in the Crowsnest River, Alberta. Percentage of infected Tubifex tubifex worms actively shedding triactinomyxons (TAMs) exceeded known thresholds of Mc establishment and TAM densities instream exceeded thresholds known to cause ≥90% declines in RNTR populations. Mc was detected at 5 of 6 study sites in water, fish, and worms. Disease severity was highest in the lower watershed where 100% of sentinel fish tested positive for Mc 7 to 14 days post-exposure; up to 85% of wild fingerling RNTR showed clinical signs of disease and yearling trout were largely absent from the river suggesting reduced survival. Our findings indicate conditions necessary for outbreak of WD exist in Alberta, highlighting the need to consider this disease as an emerging threat to wild salmonid populations.

中文翻译：

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Crowsnest 河中的旋风病：对艾伯塔省野生鲑鱼的新威胁

加拿大渔业和水产科学杂志，提前印刷。
我们提供了第一个记录在案的旋风病 (WD) 对加拿大野生、自给自足的虹鳟鱼 (RNTR、Oncorynchus mykiss) 种群的影响的案例。WD 的病原体 Myxobolus brainis (Mc) 于 2016 年在艾伯塔省首次得到证实。 然而，当地鱼类种群患病的证据尚不清楚。我们使用证据权重方法检查了艾伯塔省 Crowsnest 河中的多个寄生虫生命周期阶段。受感染的 Tubifex tubifex 蠕虫主动脱落三放线菌素 (TAM) 的百分比超过了 Mc 建立的已知阈值，并且流中的 TAM 密度超过了已知会导致 RNTR 种群下降 90% 以上的阈值。在水、鱼和蠕虫的 6 个研究地点中有 5 个检测到 Mc。下游流域的疾病严重程度最高，在暴露后 7 至 14 天，100% 的哨兵鱼检测出 Mc 阳性；多达 85% 的野生鱼种 RNTR 显示出疾病的临床症状，河流中基本上没有一岁鳟鱼，这表明存活率降低。我们的研究结果表明，阿尔伯塔省存在 WD 爆发的必要条件，强调需要将此疾病视为对野生鲑鱼种群的新威胁。