Gilad Oren, Yun Susan, Andree Karl B, Adkison Mark A, Zlotkin Amir, Bercovier Herve, Eldar Avi, Hedrick Ronald P
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
Dis Aquat Organ. 2002 Mar 11;48(2):101-8. doi: 10.3354/dao048101.
Since 1998, episodes of mass mortality have occurred in populations of common carp Cyprinus carpio carpio in Israel and in populations of koi Cyprinus carpio koi in Israel and the USA. A herpesvirus isolated from infected fish has been shown in experimental studies to induce disease and mortality similar to those observed in outbreaks at infected farms. Initial characteristics of the virus show that it is clearly different from Herpesvirus cyprini (CHV), the most commonly known herpesvirus from cyprinid fish. The koi herpesvirus (KHV) has 31 virion polypeptides. Twelve of the virion polypeptides of KHV have similar molecular weights to those of CHV and 10 are similar to those of channel catfish virus (CCV). Both virion polypeptide and restriction fragment length polymorphism analyses of genomic DNA showed that the first KHV isolates from Israel and the USA were identical. In contrast, the genomic DNA restriction fragments clearly distinguish KHV from CHV and CCV. A polymerase chain reaction (PCR) assay to detect the virus in koi tissues was developed with sequences obtained from 1 restriction fragment of KHV DNA. The PCR assay effectively detected a 484 base pair sequence from KHV but did not amplify genomic DNA from either CHV or CCV. The PCR assay detected as little as 1 pg of KHV DNA mixed with 100 ng of host DNA. Viral sequences were amplified from koi obtained from field collections and from koi that were experimentally exposed to 10(2) TCID50 ml(-1) of KHV via the waterborne route. All KHV exposed fish dying of infection between 8 and 10 d post exposure or surviving to 14 d post exposure were found to be positive by PCR, while unexposed control koi were all negative. The assay also showed the presence of KHV DNA in tissues of koi obtained from farms in Israel. The PCR assay should assist virus isolation procedures and histologic and electron microscopic analyses now commonly used to detect KHV infection. Current studies are examining the possibility of using the PCR to detect KHV DNA in live fish and the relative sensitivity and specificity of the KHV PCR assay compared with other diagnostic tests.
自1998年以来，以色列的鲤鱼种群以及以色列和美国的锦鲤种群中都发生了大规模死亡事件。在实验研究中，从受感染鱼类中分离出的一种疱疹病毒被证明能引发与受感染养殖场疫情中观察到的疾病和死亡情况相似的症状。该病毒的初步特征表明，它与鲤科鱼类中最常见的疱疹病毒——鲤疱疹病毒（CHV）明显不同。锦鲤疱疹病毒（KHV）有31种病毒粒子多肽。KHV的12种病毒粒子多肽的分子量与CHV的相似，10种与斑点叉尾鮰病毒（CCV）的相似。对基因组DNA的病毒粒子多肽分析和限制性片段长度多态性分析均表明，来自以色列和美国的首批KHV分离株是相同的。相比之下，基因组DNA限制性片段能清楚地将KHV与CHV和CCV区分开来。利用从KHV DNA的1个限制性片段获得的序列，开发了一种用于检测锦鲤组织中该病毒的聚合酶链反应（PCR）检测方法。该PCR检测方法能有效检测到KHV的一段484个碱基对的序列，但不会扩增CHV或CCV的基因组DNA。该PCR检测方法能检测到低至1 pg与100 ng宿主DNA混合的KHV DNA。从野外采集的锦鲤以及通过水传播途径经实验暴露于10² TCID50 ml⁻¹ KHV的锦鲤中都扩增出了病毒序列。所有在暴露后8至10天因感染死亡或存活至暴露后14天的经KHV暴露的鱼类经PCR检测均呈阳性，而未暴露的对照锦鲤均为阴性。该检测方法还表明，从以色列养殖场获得的锦鲤组织中存在KHV DNA。PCR检测方法应有助于目前常用于检测KHV感染的病毒分离程序以及组织学和电子显微镜分析。目前的研究正在探讨使用PCR检测活鱼中KHV DNA的可能性，以及KHV PCR检测方法与其他诊断测试相比的相对灵敏度和特异性。
