Abstract
The Japanese flounder Paralichthys olivaceus weighing an average of 73 g were intraperitoneally inoculated with Edwardsiella tarda and then the discharge of the bacterial cells from the fish were examined at 12 h intervals after bacterial challenge by using Salmonella - Shigella agar. The infected fish began to shed E.. tarda cells one to six days before death. The number of cells shed from the dead fish reached to 107-108 CFU / fish·min, and the same level of bacterial shedding was kept for several days after death. When the Japanese flounder were challenged by an immersion method, the discharged cells from the dead fish exhibited higher virulence than cultured cells on Trypto-Soya agar. These results suggest that bacteria shed from diseased fish play an important role in spreading of edwardsiellosis among cultured population of the Japanese flounder.
