Journal of Fishery Sciences of China (中国水产科学) 2013/20:6 PP.1303-1309
By using cell culture and virus infection methods, a virus had been isolated from gibel carp (Carassiusauratus gibelio) suffering with severe hemorrhage, which were cultured in a circulation aquaculture system in Wuhan,and then identified as Cyprinid herpesvirus 2(CyHV-2), designated as CyHV-2 WH strain, by electron microscopy observation, nested-PCR and viral DNA sequencing and sequence alignment analysis. The tissue homogenate of diseased fish could cause typical cytopathic effect in Koi-Fin cells. In artificial infection test, the typical symptoms of hemorrhage could be reproduced as naturally infected fish by infecting both tissue homogenate and cell cultured virus, and the death rate reached 100%. Electron microscopy observation of ultra-thin section samples of spleen and kidney tissues revealed that the viral nucleocapsid was spherical in shape measuring 110–120 nm in diameter with a 170–200 nm envelope. The virions replicated and assembled in nucleus. A 357 bp DNA fragment obtained by the nested-PCR assay of both tissue homogenate and cell culture. Sequence alignment analysis of the DNA fragment showed that WH shared so high identity (>99.44%) with the published DNA helicase gene sequence of CyHV-2 stains in GenBank, meanwhile, it shared 81.55% identity with CyHV-3 stains. Phylogenetic analysis showed that WH strain formed an independent branch on the phylogenetic tree with other CyHV-2 strains such as JS2012, H.Fukuda and YC110907.