一种从鸭新分离的黄病毒研究初报

A Brief Report of Flaviviruses Newly Isolated from Duck

从以产蛋下降为主的樱桃谷种鸭以及出现神经症状的雏鸭各分离出1株病毒,分别命名为BZ株和LC株。该2株病毒对SPF鸡胚和健康鸭胚均能产生相同的病变,分离病毒不能凝集鸡、鸭、鹅、鸽等的红细胞,在鸭胚成纤维细胞(DEF)能够产生典型的细胞病变(CPE),电镜下观察到约50nm的病毒粒子。病理组织学研究表明,二者在临床上均可导致脑组织危害,表现为脑膜水肿、血管充血和皮质层神经胶质细胞增生等。血清学检测表明,分离病毒与禽流感病毒(AIV)、鸭瘟病毒(DEV)、新城疫病毒(NDV)等病原无交叉。生物学特性鉴定该病原为有囊膜单股RNA病毒。利用不同禽病的特异性引物分别进行PCR或RT-PCR,均未扩增出特异条带。设计随机引物进行RT-PCR,扩增出基因片段,利用GenBank进行Blast同源比较,结果发现,分离病毒与以色列火鸡脑膜脑炎病毒(Israel turkey meningo-encephalitis virus,TMEV)和在马来西亚发现的Tembumu病毒至少在2段基因上具有较高的同源性,属于黄病毒属。测序表明,分离病毒与Tembumu病毒的非结构蛋白(NS5基因)和囊膜蛋白(E基因)的核苷酸同源性为86.7%～90.2%和87.0%～91.8%,与TMEV的NS5基因和E基因的同源性为72.4%～73.2%和72.7%～72.8%。2分离株之间E基因和NS5基因的核苷酸同源性均为99.5%。血清中和试验表明,BZ株阳性血清可以中和LC病毒,因此证实二者可能是同一种病毒。综合以上研究,建议将该病命名为"鸭病毒性脑炎"(Duck viral encephalitis disease)。

Two new viruses named BZ and LC,which were isolated from layer cherry duck flocks with typical eggs drop symptoms and young cherry duck with neurological signs,could replicate well not only in 10-day old SPF chicken embryos and duck embryos with typical pathological lesions but also in duck embryos fibroblast cell with cytopathogenic effect（CPE）.The viruses were approximately 50 nm in size under election-microscope with no hemagglutinating activity to erythrocytes of chicken,duck,goose and pigeon et al.Perivascular cuffing,edema and glial nodule formation in the brain were the main changes observed consistently in almost sick ducks that showed neurological signs.The serum tests indicated that there were no reactions against avian influenza virus,Newcastle disease virus,duck enteritis virus and other avian disease et al.The identifications of the viruses suggested that these viruses belong to a single-stranded RNA with an envelope.The cDNA fragments of the two viruses were amplified with specific primers corresponding to NS5 and envelope（E） gene of flaviviruses in GenBank after the virus being identified to be related to the flavivirus using random primers.Alignment analysis of nucleotide homology showed that the two viruses shared more than 99.5% homologous both in NS5 gene and E gene,which suggested that the BZ strain and LC strain maybe belong to the same virus.Further more,the isolates shared 86.7%—90.2%（87.0%—91.8%） comparing with Tembumu virus from Malaysia in view of NS5 gene（E gene）,but comparing with Israel turkey meningoencepholitis virus only 72.4%—73.2%（72.7%—72.8%）,which suggested that there were more close relationships between Tembumu virus in Malaysia and the new isolates.It is reasonable to name the disease as duck viral encephalitis.