疑患EMS/AHPNS对虾中检出黄头病毒的一种新株型

摘要

Twelve shrimp suspicious of EMS/AHPNS (early mortality syndrome/acute hepatopancreas necrosis syndrome) infection were collected from three shrimp farms in Hebei,Fujian,and Guangdong Provinces of China during 2012 and 2013.The samples were investigated in histopathological methods,nested RT-PCR following OIE protocol,and highly sensitive and rapid detection kit for yellow-head virus (YHV) detection.All of the samples showed similar symptoms,including pale and partially atrophying hepatopancreas,empty stomach and gut,and slightly whitish abdomen muscle.Histopathological examination showed that the lesions were with infiltration of hemocytes,loosen epithelium of tubule,and secondary infection of bacteria in hepatopancreas,pyknosis,and karyorrhexis,and cytoplasmic inclusions in hemocytes and lymphoid organ.Eight samples out of 12 were detected YHV-positive by nested RT-PCR protocol,of which the sensitivity for the samples seems very low.After sequencing and BLAST on NCBI,the sequences of the RT-PCR products shared 76.5％ to 89％ similarity common to the YHV reported previously.The phylogenetic tree of the target sequence showed that the samples from the three provinces occupy a same branch that is different from known YHV/GAV (gill-associated virus) strains,having closer relationship to YHV than to GAV.With the newly developed detection kit for YHV,all of the samples were detected strongly positive.The results indicate that the farmed shrimp suffering from AHPNS in China were infected by a new genotype YHV.This is the first case of YHV detected in China.%对2012-2013年从河北、福建和广东3个对虾养殖场采集的12份发生疑似早期死亡综合征/急性肝胰腺坏死综合征(EMS/AHPNS)的样品,采用组织病理学方法、套式RT-PCR检测方法以及快速灵敏检测试剂盒进行了检测.三地来源的养殖对虾样品症状均表现为肝胰腺颜色变淡,部分出现萎缩,空肠空胃,腹节肌肉略微白浊;组织病理切片结果表明,患病对虾肝胰腺血细胞浸润,肝胰腺盲管上皮细胞脱落,继发性细菌感染,淋巴器官和血淋巴细胞内存在核固缩、破裂和细胞质包涵体. 按世界动物卫生组织(OIE)手册的套式RT-PCR方法检测,结果显示,黄头病毒(Yellow head virus,YHV)目的产物的阳性样品检出率为66.7％,该方法对这些样品的灵敏度可能很低.目的产物测序后经NCBI Blast,与已报道的YHV相似性为76.5％-89％;系统发育树显示这3个来源的样品位于同一个分支,与已知的YHV/鳃联病毒(gill-associated virus,GAV)株均不相同,其亲缘关系与YHV较近,而与GAV较远.用新研发的YHV快速高灵敏检测试剂盒检测,结果表明,所有样品均为YHV强阳性.以上表明患AHPNS的养殖对虾中存在一种YHV的新株型的感染,这也是我国首次检测到YHV的感染.