Infection-cycles of Renibacterium salmoninarum in hatcheries of masu salmon Oncorhynchus masou by monitoring specific antibodies

Detection of antibodies against Renibacterium salmoninarum (R.s.), a causative agent of bacterial kidney disease (BKD), was conducted among apparently healthy fingerlings and broodstock of masu salmon Oncorhynchus masou. Antibodies against R.s. were detected from >= 50% of fingerlings in the hatcheries with BKD-histories and R.s. antigens were detected in some of antibody-positive fish, but not from those in the hatchery without a BKD-history. Although returning broodstock examined within two weeks after introduced into the hatchery showed all negative for anti-R.s. antibodies, 33% of those in the hatchery with BKD-histories became positive after two months of rearing for sexually maturation. Monitoring specific antibodies suggests that R.s. infection-cycle is completed between fingerlings and broodstock in hatcheries having BKD-histories.