Abstract
An undescribed virus was isolated from the brain of coho salmon (Oncorhynchus kisutch), iwana (Salvelinus pluvius), rainbow trout (O. mykiss) and ayu (Plecoglossus altivelis), and ovarian fluid of masu salmon (O. masou) cultured in the northern part of Japan. The virus was isolated from both juveniles and adult fishes. Diseased fish showed abnormal swimming movement and were lethargic. The virus replicated, inducing cytopathic effects and lysis in susceptible cell lines at temperatures of 5 to 25°C. Persistent infection was observed in several fish cell lines. The virus particles were enveloped, and were icosahedral in shape with about 80 nm in diameter with a central electron-dense core. The virus was replicated with IUdR and BVdU, and inclusion bodies in the infected cells were stained with acridine orange. The virus density was 1.155g/ml and the viral RNA was 7.3kb in length. The virus was stable to pH, diethyl ether and chloroform. The virus was not neutralized by antisera against known 6 fish viruses.
