Viral diseases of fish in Japan.

Viruses causing infectious pancreatic necrosis (IPN) and infectious hematopoietic necrosis (IHN) were first isolated in Japan during the 1970s and these two diseases remain among the most serious problems affecting cultured salmonids in Japan. In addition to IHN and IPN, four other viral diseases cause major economic losses among cultured fishes in Japan. These include viral pancreatic hepatic necrosis of yellowtail, rhabdovirus infection of Japanese flounder and black rock fish, Kuchishiro-sho of tiger puffer fish, and epidermal hyperplasia or necrosis of Japanese flounder. Over the years, a number of other viruses have been isolated from, or have been observed by electron microscopy, in moribund fish. Members of 10 of the existing families of animal viruses are represented in this group. Their importance to the aquaculture industry in Japan is reviewed here.