Date of this Version
A newly recognized virus, lethal for fry and fingerlings, has been isolated from brood stock rainbow trout (Salmo gairdneri) at the Winthrop National Fish Hatchery, Washington. A similar if not identical virus has been found in natural epizootics occurring annually since 1970 among fry of landlocked sockeye salmon (Oncorhynchus nerka) on Honshu Island, Japan. More recently, this agent was isolated from moribund and dead adult O. nerka on Hokkaido Island; Japan, but it remains to be determined whether or not the virus causes death in adult salmonids. The purpose of this leaflet is to bring the new agent to the attention of diagnosticians and researchers. It is recognized that some aspects of the virus and its effect upon host species are still incompletely known.