PATHOGENICITY OF THE VIRUS ISOLATED FROM BRAIN OF ABNORMALLY SWIMMINGSALMONID

Pathogenicity of the new virus isolated from the brain of coho salmon Oncorhynchus kisutch was investigated by waterborne and intramuscular inoculation to coho salmon, masu salmon O. masou, iwana Salvelinus plu vius, steelhead trout O. mykiss, and ito Hucho perryi. Typical disease signs of spinning swimming and lethargic behavior were observed in th e experimentally infected fishes. The cumulative mortality of coho sal mon fry for 60 days bathed with the virus reached 6 to 34%. In intramu scular injection of the virus, cumulative mortality of coho salmon fry reached 51 to 63%. The virus also showed pathogenicity to masu salmon , steelhead trout and iwana. Virus antigen was detected by indirect fl uorescent antibody test (IFAT) in the kidney, brain and blood cells of the infected fish.