National Veterinary Institute, Oslo and Bergen, Norway.
J Fish Dis. 2010 Nov;33(11):879-88. doi: 10.1111/j.1365-2761.2010.01190.x.
Pancreas disease (PD) is an important cause of losses in farmed salmonids in Norway, the United Kingdom and Ireland. As the spread of salmonid alphavirus (SAV), the causal agent, to naïve populations is of major concern to the farming industry, it is important to uncover the transmission routes of the virus. This study was conducted to investigate the potential for vertical transmission of SAV subtype 3. Progeny of broodstock with signs of late-stage PD and persistent RT-PCR signals for SAV were followed from fertilization to smoltification in an experimental facility. Fertilized ova were either not disinfected or taken through one of three different disinfection regimes. Also, ova and milt from uninfected broodfish from a different population were exposed to a cell-cultured strain of SAV 3 immediately before fertilization to simulate a viraemic phase in parent fish. A group of uninfected controls were also included in the study. Fertilized ova from bath exposed and negative control groups were double disinfected. Following fertilization, experimental fish went through a normal freshwater phase. However, fry were stressed at first feeding to enhance replication of possibly latent virus. Smoltification was induced by an artificial light regime, and experimental fish were followed to the late smoltification phase. Selected samples were investigated by real-time RT-PCR for SAV, by histology for evidence of PD and by serology for neutralising antibodies against SAV. All analysed samples of progeny were negative. This result shows that SAV 3 is not readily transmitted vertically from parents to offspring. Additional negative PCR results from salmon sampled in commercial hatcheries support these findings. Also, recent studies have shown that risk factors for the horizontal transmission route explain the vast majority of PD outbreaks in Norway. It is concluded that if it happens at all, vertical transmission is of minor importance in the spread of SAV 3.
胰腺疾病（PD）是挪威、英国和爱尔兰养殖鲑鱼损失的重要原因。由于鲑鱼甲病毒（SAV）的传播，即病原体，对养殖行业来说是一个主要的关注问题，因此了解病毒的传播途径非常重要。本研究旨在调查 SAV 亚型 3 垂直传播的可能性。对有晚期 PD 迹象和持续 SAV RT-PCR 信号的亲鱼的后代，在实验设施中从受精到变态进行跟踪。受精卵要么不消毒，要么经过三种不同的消毒方案之一。此外，来自不同种群的未感染亲鱼的卵和精液在受精前立即暴露于细胞培养的 SAV 3 株，以模拟亲鱼中的病毒血症阶段。研究还包括一组未感染对照。受浴暴露和阴性对照组的受精卵进行了双重消毒。受精后，实验鱼经历了正常的淡水期。然而，幼鱼在第一次进食时受到压力，以增强可能潜伏的病毒的复制。通过人工光照诱导变态，并跟踪实验鱼进入晚期变态阶段。选择的样本通过实时 RT-PCR 检测 SAV，通过组织学检查 PD 证据，通过血清学检测针对 SAV 的中和抗体。所有分析的后代样本均为阴性。这一结果表明，SAV 3 不易从亲代垂直传播给后代。从商业孵化场采集的鲑鱼的额外阴性 PCR 结果支持了这些发现。此外，最近的研究表明，水平传播途径的风险因素解释了挪威绝大多数 PD 爆发的原因。因此，可以得出结论，如果存在垂直传播，它在 SAV 3 的传播中也只是次要的。
