养殖大黄鱼“白鳃病”一种新病毒病原的初步研究

Preliminary study of a new virus pathogen that caused the white-gill disease in cultured Larimichthys crocea

运用组织病理学、电镜观察及PCR扩增等方法对近年来网箱养殖大黄鱼暴发的"白鳃病"进行了研究,以探讨引起养殖大黄鱼"白鳃"关联病毒的致病机理。临床解剖观察显示:患"白鳃病"的鱼表现出极度的贫血症状、鳃丝苍白色、血液稀薄且血细胞数显著减少;内脏组织病理观察结果显示:鱼的肝、脾、肾脏内脏组织发生严重的病理变化,组织内红细胞发生明显的退行性变化,同时鱼体的红细胞数量显著减少;采用针对真鲷虹彩病毒(red sea bream iridoviral virus,RSIV)的引物对病鱼内脏组织核酸样本进行PCR检测,结果显示,患"白鳃病"病鱼样本RSIV核酸呈阴性;组织超薄切片电镜观察结果显示:在患"白鳃病"病鱼脾脏和肾脏组织细胞的胞质中可见直径约40~45 nm的病毒粒子。由此初步判断,浙江地区网箱养殖大黄鱼的"白鳃病"不是由RSIV导致,而与一种直径为45~50 nm的病毒有直接关联,本研究为大黄鱼疾病的诊断与防治提供了参考依据。

By using histopathology and polymerase chain reaction（PCR） methods, studies were carried out to find the cause of the white-gill disease in Larimichthys crocea cultured in cage in Zhejiang Province. White-gill diseased fish had the typical symptom of pale gills and there is no ulcer in the body surface of infected fish.However, the blood and blood cell counts in the white-gill disease fish were significantly decreased. Pathological observation showed serious pathological changes in internal organs. In white-gill diseased fish, haemocytes, in particular, erythrocytes reduced sharply in the blood vessels of liver, spleen and other organs and degenerative changes occurred in red blood cells, too. Under electron microscope, a large number of viral particles were observed in the cytoplasm of spleen, with an average diameter of 40 to 45 nm. With the primers derived from RSIV, no fragments of the RSIV DNA could be amplified from the white-gill diseased fish. The results indicated that although white-gill disease and RSIVD both can lead to the symptom of pale gills, but the pathogen that caused each disease was completely different, and the white-gill disease that broke out in Zhejiang may be associated with another virus.