神經壞死病毒 (Nervous necrosis virus, NNV) 的感染易造成石斑魚魚苗及幼魚在養殖期間爆發病毒性神經壞死症 (Viral nervous necrosis disease, VNN disease)，使魚苗大量死亡，因而造成漁民及經濟重大的損失。該病毒帶有兩條單股 RNA ，分別為 RNA1 與 RNA2，其中 RNA1 的功能為RNA-dependent RNA polymerase；RNA2 則可轉譯出病毒的外殼蛋白質。從神經壞死病毒爆發的現象發現，在高溫時魚體爆發病毒性神經壞死症的情形比低溫時嚴重，因此我們欲分析神經壞死病毒在魚體內的複製能力與溫度及魚隻大小的關係。在本研究中，我們於 2010年至 2012年期間，至台南及高屏地區數個石斑魚養殖場中收集健康及罹患病毒性神經壞死症之魚苗，利用實驗室先前所分離並培養的神經壞死病毒株建立了病毒對石斑魚的感染模式系統，將病毒腹腔注射至不同魚齡的魚體後，培養在 20℃ 與28℃ 的環境，再利用 Real-time PCR 及病理組織學的方法來偵測神經壞死病毒在魚體內的病毒分佈情形，觀察病毒是否會因為溫度的差異和魚隻的大小，影響病毒複製的能力。結果發現，病毒在 28℃ 環境下時會加快病毒的複製速度，在 20℃ 環境下則會降低病毒的複製速度，而幼魚比魚苗對於神經壞死病毒有更高的耐受性。 Nervous necrosis virus (NNV) threatens larvae and juveniles hatchery production in Taiwan. This virus causes massive mortality in grouper juveniles by viral nervous necrosis disease (VNN) and result in considerable economic losses in grouper aquaculture. NNV contains two, single stranded, positive-sense RNA called RNA1 and RNA2. RNA1 encodes RNA dependent RNA polymerase, and RNA2 encodes viral coat protein. From the observation of nervous necrosis virus outbreak in the farm, we found that temperature change could affect virus infection ability. Therefore, we would like to investigate whether the virus replication rate is affected directly by the grouper size or incubation temperature. In our study, we collected VNN diseased orange-spotted grouper samples from several aquaculture farms near Tainan from year 2010 to 2012. We established NNV challenge model by intraperitoneal injection of NNV to healthy grouper. We also use Real-time PCR and histopathological methods to detect the amount of NNV present in various tissue sample of infected and healthy grouper. Finally, we hope to find the relationship between temperature and NNV infection to reduce the impact of NNV infection in grouper aquaculture industry. Results demonstrated that virus replicate slower in 20℃ and replicate faster in 28℃. In addition, grouper juveniles are more tolerance for virus than larvae.
