Control of viral nervous necrosis in merine fish

病毒性神经坏死（VNN）是一种新出现的疾病，主要发生在日本斑纹鱼（striped jack Pseudocaranx dentex）等海鱼的孵化场饲养仔鱼和幼鱼中。斑马鱼VNN的病原鉴定为诺达病毒（诺达病毒科）。在东南亚、澳大利亚和欧洲也报告了与VNN相似的海鱼疾病。在斑jack的VNN中，育雏群是病毒最重要的接种源，因此，消除携带病毒的产卵者被认为是有效的预防幼虫的疾病。尽管通过elisa诊断去除含有抗体的产卵体降低了疾病发生率，但从抗体阴性产卵体获得的一些幼虫群中仍然发生疾病，这表明没有抗体并不一定意味着产卵体中没有病毒。下一步，我们应用PCR扩增技术在产卵前检测产卵者生殖腺的病毒，将病毒阳性的产卵者从产卵群中剔除。结果表明，该方法对幼虫生产中VNN的预防是非常有效的。

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.