Abstract:In April 2016, a serious infectious disease characterized by hemorrhage of the gill, swim bladder, and internal organs emerged in a farm in Sichuan Province. Histopathological observation showed that the spring viremia of carp virus (SVCV) infection in could cause pathological damages in multiple organs, which exhibited hemorrhage, degeneration, necrosis, and infiltration of the inflammation cells, especially in the liver, spleen, kidney, gill, and intestine. The filtrated homogenate was inoculated into the epithelioma papulosum cyprini (EPC) cells, and the typical cytopathic effect (CPE) was formed after three blind passages. Diseased tissue suspension filtered from bacteria and EPC-grown virus were used to inoculate healthy developed similar clinical symptoms to those described above and suffered 60% and 50% mortality, whereas the control group remained normal. Transmission electron microscopy (TEM) of EPC cells infected with ZLP160415 found that the virus was bullet-shaped, 90-150 nm long, and 40-60 nm wide. RT-PCR of tissue homogenates from the fish naturally infected, the fish artificially infected, and the infected cells were performed, and the results showed that all were SVCV-positive. Based on phylogenetic analysis of glycoprotein genes, the isolate ZLP160415 was classified into the Ia genogroup. From the combination of epidemiology, pathologic lesions, virus isolation and identification, artificial infection, and TEM examination, it was concluded that the SVCV was the pathogen of the disease.