Institute for Infectious Diseases and Zoonoses, Department for Veterinary Sciences, LMU Munich, 80539 Munich, Germany.
Bavarian Environment Agency, Unit Aquatic Toxicology, Pathology, 82407 Wielenbach, Germany.
Viruses. 2019 Jan 28;11(2):112. doi: 10.3390/v11020112.
The proliferative darkening syndrome (PDS) is a lethal disease of brown trout () which occurs in several alpine Bavarian limestone rivers. Because mortality can reach 100%, PDS is a serious threat for affected fish populations. Recently, Kuehn and colleagues reported that a high throughput RNA sequencing approach identified a piscine orthoreovirus (PRV) as a causative agent of PDS. We investigated samples from PDS-affected fish obtained from two exposure experiments performed at the river Iller in 2008 and 2009. Using a RT-qPCR and a well-established next-generation RNA sequencing pipeline for pathogen detection, PRV-specific RNA was not detectable in PDS fish from 2009. In contrast, PRV RNA was readily detectable in several organs from diseased fish in 2008. However, similar virus loads were detectable in the control fish which were not exposed to Iller water and did not show any signs of the disease. Therefore, we conclude that PRV is not the causative agent of PDS of brown trout in the rhithral region of alpine Bavarian limestone rivers. The abovementioned study by Kuehn used only samples from the exposure experiment from 2008 and detected a subclinical PRV bystander infection. Work is ongoing to identify the causative agent of PDS.
增生性黑化综合征（PDS）是一种发生在巴伐利亚高山石灰岩河流中的致命性褐鳟疾病。由于死亡率可能达到 100%，PDS 对受影响的鱼类种群构成了严重威胁。最近，Kuehn 及其同事报告称，高通量 RNA 测序方法鉴定出一种鱼类正呼肠孤病毒（PRV）是 PDS 的致病因子。我们调查了 2008 年和 2009 年在伊勒河进行的两次暴露实验中受 PDS 影响的鱼类样本。使用 RT-qPCR 和经过验证的下一代 RNA 测序病原体检测方法，2009 年 PDS 鱼类中未检测到 PRV 特异性 RNA。相比之下，2008 年患病鱼类的多个器官中可轻易检测到 PRV RNA。然而，未接触伊勒河水且未出现任何疾病迹象的对照鱼中也可检测到类似的病毒载量。因此，我们得出结论，在高山巴伐利亚石灰岩河流的 rhithral 区域，PRV 不是褐鳟 PDS 的致病因子。Kuehn 等人的上述研究仅使用了 2008 年暴露实验的样本，并通过检测到亚临床 PRV 伴随感染。目前正在努力确定 PDS 的致病因子。
