Abstract
Pathogenicity of an isolate (CSH9003) of salmonid herpesvirus 2 from maricultured coho salmon (Oncorhynchus kisutch) to coho salmon, masu salmon (Oncorhynchus masou) and rainbow trout (Oncorhynchus mykiss) was compared with those of NeVTA, OMV and YTV. Injections of CSH9003 resulted in high mortality in coho salmon and lower mortality in masu salmon, while no mortality was observed in rainbow trout. In contrast, NeVTA from kokanee and OMV and YTV from masu salmon showed high virulence to masu salmon and lower virulence to coho salmon and rainbow trout. The susceptivility of coho salmon to artificial infection with CSH9003 decreased with the size of fish, although CSH9003 showed lethal pathogenicity to even fish weighing 200g. Mortality caused by the injections of CSH9003 and CSH9104 both isolated from dead coho salmon were similar to that caused by CSH9117-T isolated from the basal cell tumor tissue. In survivors of CSH9003-injected coho salmon fry, the basal cell tumor was found on the gill filament about 18 months after inoculation.
