| Summary: | Pathogenicity of the Rhabdovirus olivaceus (hirame rhabdovirus; HRV) against salmonid fish (rainbow trout; Oncorhynchus mykiss, masu salmon; O. masou, chum salmon; O. keta, coho salmon; O. kisutch and pink salmon; O. gorbuscha) was studied. Artificially infected salmonid fish with HRV by water-born and I.P. injection were reared at 12 to 14 ℃. Signs and mortalities of HRV infected fish were observed and also histopathological changes were studied. Cumulative mortalities of HRV infected rainbow trout, chum, coho and pink salmon by water-born infection were 8, 4, 4, and 0 %, respectively. Mortalities of rainbow trout, masu, chum, and coho salmon by I.P. injection were 55, 30, 25, and 5 %, respectively. Highest virus titer was obtain from the rainbow trout infected by both infection methods. Mortalities of rainbow trout weighing 0.2, 0.5, and 3.0g were 100, 55, and 40 %, respectively. And mortalities of rainbow trout infected with HRV and IHNV were 40 and 100%, respectively. Histopathologically, on the HRV injected rainbow trout, the kidney and spleen indicated necrosis and hemorrhage, skeletal muscle revealed hyperemia and hemorrhage. In rainbow trout infected with HRV or IHNV similar changes were observed in the kidney and spleen, but in HRV infected fish, no pathological changes were found in the liver of early stages, and necrosis was not observed in the intestine. Oji International Symposium on Salmonid Diseases. 22-25 October 1991. Sapporo, Japan
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