Infectious pancreatic necrosis virus and infectious hematopoietic necrosis virus were isolated in the 1970's. These two viral diseases are still serious problems among the cultured salmonids in Japan. Since then, various viral infections of fish have been reported, more than 20 fish viruses have been isolated and more than five viruses have been observed by electron microscopy. Six viral diseases are major problems and cause economic losses among cultured fishes in Japan. These are IPN and IHN of salmonids, viral pancreatic-hepatic necrosis of yellowtails, rhabdovirus infection of Japanese flounder and black rock fish, "Kuchishiro-sho" of tiger puffer and epidermal necrosis of Japanese flounder. Besides these, there are several viral infections: herpesvirus infections of salmonids, especially epithelial tumor (induced by OMV or YTV); epithelial tumor of carp (Herpesvirus cyprini); and lymphocystis disease of several marine fishes. Eel virus from the European eel, eel virus of America and eel virus of Europe X were also isolated from cultured eel. Recently however, many other viruses were isolated from diseased and healthy fishes, including icosahedral cytoplasmic deoxyribovirus, papovavirus, herpesvirus, picornavirus and reovirus from cultured eel. Chum salmon virus was isolated from masu salmon. Reovirus and Coronavirus cyprini were isolated from common carp and birnavirus was isolated from Japanese flounder and red sea bream. In the blood of salmonids, the causative agent of viral erythrocytic necrosis was observed and in moribund fry of ishidai and epithelial necrosis of black sea bream and red sea bream, picornavirus and paramyxovirus were observed by E.M.The Second Asian Fisheries Forum. 17-22 April 1989. Tokyo, Japan
