罗氏沼虾苗肌肉白浊病病原的初步研究

PRELIMINARY STUDIES ON THE WHITISH MUSCLE DISEASES OF MACROBRACHIUM ROSENBERGII POST-LARVAE

收集罗氏沼虾肌肉白浊病典型病虾苗 ,进行细菌分离、除菌组织悬液制备及人工感染试验、超薄切片、病毒粗提取 ,结果表明 :从白浊病病虾的肌肉、肝胰腺中分离到的细菌以5× 1 0 8CFU/mL浓度浸泡感染正常沼虾苗不能复制疾病 ;病虾除菌组织过滤液以 1∶5 0、1∶2 5 0浓度浸泡感染正常虾苗 ,7d后可发病 ,并出现典型的肌肉白浊病症状 ,氯仿处理不能破坏病毒的感染力 ;病虾超薄切片电镜观察发现肌肉间隙组织中存在 2 1— 2 3nm大小的球状病毒 ,病虾组织浆经氯仿处理、PEG沉淀、磷钨酸负染后可见到大量 2 2— 2 4nm大小的球状病毒颗粒。上述结果表明罗氏沼虾肌肉白浊病是一种由病毒引起的疾病。

A new epidemic spread out recently years in the larvae and post larvae of giant freshwater prawn, Macrobrachium rosenbergii, in many hatcheries of some South China provinces.The diseases,with the symptom of whitish muscle in abdomen or opacity muscles,was called as whitish muscle diseases,causing serious loss of M.rosenbergii larvae or post larvae. The typical diseased post larvae were used for bacteria isolation, tissue homogenizing and artificial challenging test with health M.rosenbergii larvae by immersion infection tests.The health larvae could not be infected by the bacteria strains isolated from hepatopacreas and muscles of diseased larvae in two weeks after infection at the concentration of 5×10 8 CFU/ml,but could be infected by bacteria free tissue homogenate at concentration of 1∶50 and 1∶250,with symptom similar of the nature diseased shrimps,7 days after challenging.The infectivity could not be inactived by 10% chloroform. With the ultrathin section, spherical virions were found with the size of 21-23nm in the muscle connection. The virus partly purification was carried out with diseased larvae homogenized in PBS,treated with chloroform followed by PEG precipitation and 2% PTA negative staining.It could be found plenty of spherical virions with the size of 22-24nm.These results showed that the whitish muscle disease of M.rosenbergii post larvae was caused by this virus.