In this study, by using electron microscopy technique , a viral agent associated with massive mortality in cage -farmed tilapia was discovered for the first time at home .The results showed that numerous viral particles were observed in the cytoplasm of spleen, heart and gill tissues, etc.The viral particles are spherical, non-enveloped, with a diameter of 30 ~40nm, which was similar to the nervous necrosis virus in fishes .%利用电子显微镜技术，首次在国内从患暴发性流行病罗非鱼体内发现病毒病原。电镜观察结果显示，在患病罗非鱼脾脏、心脏以及鳃组织细胞质中观察到大量病毒颗粒。病毒颗粒呈球形，无囊膜，直径约30～40 nm，与鱼类神经坏死病毒相近。
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