Control of viral nervous necrosis in merine fish

病毒性神经坏死(VNN)是日本斑点石斑鱼等海水鱼类幼、幼鱼的一种新出现的疾病。经鉴定，该病毒为诺达病毒(Nodaviridae)。东南亚、澳大利亚和欧洲也报告了类似VNN的海洋鱼类疾病。在横纹夜蛾的VNN中，亲鱼群是病毒最重要的接种源，因此，消灭携带病毒的产卵者被认为是预防该病毒在幼虫中的有效方法。虽然通过ELISA诊断去除具有抗体的产卵鱼降低了发病率，但从抗体阴性产卵鱼获得的一些幼虫群中仍有该病发生，这表明没有抗体并不一定意味着产卵鱼中没有病毒。在下一步中，我们应用了PCR扩增技术来检测产卵者性腺中的病毒，并将病毒阳性的产卵者从产卵组中剔除。结果证实，该程序对预防幼虫生产中的VNN非常有效。

Viral nervous necrosis(VNN)is a newly emersing disease in hatchery-reared larvae and juveniles of marine fishes such as striped jack Pseudocaranx dentex in Japan. The causative agent of VNN in striped jack was identified as a nodavirus (Nodaviridae). Diseases of marine fishes similar to VNN were also reported in Southeast Asia, Australia, and Europe. In the case of VNN in striped jack, the brood stocks were the most important inoculum source of the virus, thus, elimination of spawners carrying the virus was thought to be effective to prevent the disease in larvae. Although removal of antibody-possessing spawners by ELISA-based diagnosis reduced the rate of disease occurrence, the disease still occurred in some larval groups obtained from antibody-negative spawners, suggesting that the absence of antibody did not necessarily mean the absence of the virus in spawners. In the next step, we applied the PCR amplification technique to detect the virus from spawner's gonad just before apawning and virus-positive spawners were eliminated from spawning groups. As a result, it was confirmed that this procedure was very effective for the prevention of VNN in the larval production.