鲫鱼自然感染对虾偷死野田村病毒(CMNV)的初步研究

Preliminary Study on the Natural Infection of Carassius auratus with Covert Mortality Nodavirus(CMNV)

对虾病毒性偷死病(Viral covert mortality disease,VCMD)是由偷死野田村病毒(Covert mortality nodavirus,CMNV)引起的一种新发疫病,近年来使中国对虾养殖业遭受了严重的经济损失。为筛查对虾池塘养殖系统中CMNV的自然宿主种类,本研究在山东潍坊一个发生VCMD的凡纳滨对虾(Litopenaeus vannamei)养殖场排水渠中采集了野生鲫鱼(Carassius auratus)样品,对其携带和感染CMNV的情况进行了系统分析。逆转录套式PCR检测结果显示,鲫鱼样品的总RNA能扩增出与预期大小一致的CMNVRNA依赖的RNA聚合酶目标基因片段。组织病理和原位杂交分析显示,鲫鱼脑部神经组织空泡化严重,脑皮层锥体细胞和二叠体颗粒细胞核固缩明显,心肌呈现典型的溶解样坏死病理变化,脑和心肌组织的病变部位均可见淡紫色CMNV探针杂交信号。透射电子显微镜观测显示,鲫鱼脑中可见神经组织空泡化,心肌组织坏死严重,CMNV样病毒颗粒占据了心肌细胞内大部分区域。本研究表明,CMNV在自然条件下能够跨越物种障碍、感染对虾养殖池塘排水渠中的野生鲫鱼,并导致靶组织明显的病理损伤,同时也提示,CMNV感染其他鱼类尤其是淡水鱼类的风险值得高度关注。

Viral covert mortality disease(VCMD)is an emerging disease caused by covert mortality nodavirus(CMNV).VCMD recently resulted in severe economic losses in China due to shrimp aquaculture infections.To identify the natural hosts of CMNV in the pond culture system,samples of Carassius auratus were collected for testing purposes from the drainage channel of a shrimp farm affected by VCMD.The results of CMNV reverse transcription nested PCR showed that the RNA of C.auratus sample could be amplified and produced the expected target gene fragment.Histopathological analysis showed that CMNV infection in C.auratus caused brain nervous tissue vacuolation.Obvious karyopyknosis occurred in the corpora bigemina granular cells and cortical pyramidal cells.In situ hybridization analysis showed CMNV positive signals in regions of the brain and cardiac muscle with pathological damage.Transmission electron microscopy analysis verified the brain nervous tissue vacuolation and the presence of CMNV particles in the cardiac muscle.The results of the present study indicate that CMNV can cross the species barrier to infect fish and cause pathological damage in the target tissues.Our findings emphasize the need for paying close attention to the high risk of CMNV infections in other fish species,especially freshwater fishes.