2004 Volume 70 Issue 3 Pages 318-323
To clarify the dynamics of the infectivity of Flavobacterium psychrophilum between wild fishes and released ayu, PCR-RFLP analyses of F. psychrophilum isolated from wild fishes collected in the Kako River from April to June were performed. F. psychrophilum (BS type) isolated from pale chub was killed by the cold water disease in February, before the release of landlocked ayu of Biwako, and was isolated only from pale chub until late May. On the contrary in ayu, although an outbreak of the cold water disease was confirmed by late June, the BS type of F. psychrophilum was not detected. It was clarified that there were different strains of F. psychrophilum infecting pale chub and ayu. It was confirmed that there were differences also in the sensitivity of hosts from the challenge test in the laboratory.
