Bjørgen Håvard, Haldorsen Randi, Oaland Øyvind, Kvellestad Agnar, Kannimuthu Dhamotharan, Rimstad Espen, Koppang Erling Olaf
Institute of Basic Science and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Mowi ASA, Bergen, Norway.
J Fish Dis. 2019 Jun;42(6):935-945. doi: 10.1111/jfd.12995. Epub 2019 Apr 10.
Melanized focal changes in skeletal muscle of farmed Atlantic salmon (Salmo salar) are a major quality problem. The aetiology is unknown, but infection with Piscine orthoreovirus (PRV) has been associated with the condition. Here, we addressed the pathogenesis of red and melanized focal changes and their association with PRV. First, a population of farmed fish (PRV-negative prior to sea transfer) was sequentially investigated throughout the seawater period. The fish were autopsied and tested for PRV infection. Muscular changes were described by macroscopy and histology, and a classification system was established. Second, in an experimental infection trial, PRV was injected intramuscularly to induce changes. The farmed fish was gradually infected with PRV. Red focal changes occurred throughout the observation period with a low prevalence regardless of PRV status. Melanized changes were highly diverse and their prevalence increased during the trial. Changes of low macroscopic grade and histological category were more prevalent in PRV-negative fish. Diffuse granulomatous melanized changes only occurred after PRV infection. No muscular changes were observed in the experimentally challenged fish. Our studies do not indicate that PRV infection causes red focal changes, but seems important in the development of granulomatous melanized changes.
养殖大西洋鲑（Salmo salar）骨骼肌中的黑化灶性变化是一个主要的质量问题。其病因尚不清楚，但感染鱼类正呼肠孤病毒（PRV）与这种情况有关。在此，我们探讨了红色和黑化灶性变化的发病机制及其与PRV的关联。首先，对一群养殖鱼（在海水转移前PRV呈阴性）在整个海水养殖期进行了连续调查。对鱼进行解剖并检测PRV感染情况。通过肉眼观察和组织学描述肌肉变化，并建立了一个分类系统。其次，在一项实验性感染试验中，通过肌肉注射PRV来诱导变化。养殖鱼逐渐感染PRV。无论PRV状态如何，在整个观察期内红色灶性变化均有发生，但发生率较低。黑化变化高度多样，其发生率在试验期间有所增加。低肉眼分级和组织学类别的变化在PRV阴性鱼中更为普遍。弥漫性肉芽肿性黑化变化仅在PRV感染后出现。在实验性攻毒的鱼中未观察到肌肉变化。我们的研究并未表明PRV感染会导致红色灶性变化，但在肉芽肿性黑化变化的发展中似乎很重要。
