Isolation of the virus causing viral endothelial cell necrosis of eel from cultured Japanese eel Anguilla japonica

To isolate the causative virus for viral endothelial cell necrosis of eel (VECNE), we established the cell line JEEC, originated from vascular endothelial cells of Japanese eel Anguilla japonica. CPE with hypertrophied nuclei was found in JEEC inoculated with the filtrate of homogenized gills of diseased fish 7 days after inoculation. In the hypertrophied nuclei, icosahedral virus particles of about 75 nm in diameter were observed. The nucleic acid in the isolated virus was DNA. The virus was tolerant to chloroform and pH 3.0. It showed tolerance up to 42 degrees C. Thus, this virus was classified as an adenovirus. The experimental infection by injecting the virus at 10(5.75) TCID50 into the abdominal cavity of healthy eel produced congestion in the central venous sinus of gill lamella, which is the typical sign of this disease, with the cumulative mortality being 60%. The virus was recovered from the gills, liver and kidney of the experimentally infected fish. Therefore, the virus of VECNE was identified as the causative agent.