急性致死性对虾病的杆状病毒病原研究

THE STUDIES ON BACULOVIRUS-CAUSED DISEASE OFPRAWNS (PENACUS CHINESIS OSBECK)IN SHANGHAISUBURB

近年来，上海郊区饲养中国对虾（Ｐｅｎａｃｕｓｃｈｉｎｅｓｉｓｏｓｂｅｃｋ）的虾塘发生大面积的流行病。经对病虾的鳃、肝、胰腺或中肠组织进行超薄切片处理及电镜观察，发现在这些组织的细胞核内存在大量有囊膜包裹的杆状病毒，有时一个囊膜还可同时包裹两个病毒的核衣壳。经有机溶剂处理、差速离心及密度梯度离心，可以获得部分提纯的病毒和病毒核衣壳制剂。超薄切片中，病毒粒子大小约为４４０－５００×１７０－１８０ｎｍ，核衣壳大小约３３０－４２０×１１０－１４０ｎｍ，提纯的核衣壳粒子大小约为３５０－４００×７０－８５ｎｍ。无论在超薄切片或在分离提纯的制剂中，均未观察到有包涵体存在。将部分提纯的病毒制剂人工感染健虾，结果发现肌注的对虾死亡率达９０％以上，饲毒的死亡率各在５０％左右。这些结果证明，所发现的杆状病毒可能就是引起这次上海郊区对虾大规模死亡的主要原因。

here was an outbreak of an acute lethal disease of prawns(Penacus chinesis osbeck) in manyshrimp farms in Shanghai suburb. Electron microscopic examination of ultrathin section of theliver, pancreas and mid-gut gland tissues revealed the presence of rod-shaped baculovirus par-ticles in the affected cell nuclei.The viral nucleocapsids were surrounded by envelopes of abi-or trilaminal unit membranes. In ultra-thin section,the enveloped virus particles ranged insize of 440-500nm in length and 170-180nm in breadth,whereas the nucleocapsids insize of 330-420nm and 110-140nm respectively.Using the comination of the treatment of organicsolvent,differential and sucrose gradient centrifugations,a partial purified viral nucleocapsidpreparations could be obtained. The sizs of isolated nucleocapsids in negatively stainedsamples ranged 350-400nm in length and 70-85nm in breadth.The 10nm of periodicity ofsurface stritions of the negatively stained nucleocapsids were clearly revealed by electronmicroscopy.Occasionally,two nucleocapsids enclosed within a single envelope could be ob-served in both negatively stained preparations and ultrathin sections.No occlusionbodies have been found.Consequently,the baculovirus we observed could be a member ofsubgroup C of baculoviruses.Artificial inoculation experiments of healthy prawns were carried out either by injection orby feeding of partiadiy purified virus prepamtions. The lethal rate reached to 90% and 100%in two injection experiments,whereas the lethal rate ouly reached 50%,40% and 50% in threefeeding experiments. Moreover,the symptoms which appeared after artifcial inoculation werevery similar to those shown by the diseased prawns under natural conditions. These resultsstrongly support the conclusion that the baculovirus found by us is the lethal pathogen for theprawn disease in Shanghai.