An epidemiological study of furunculosis in salmon propagation in Japanese rivers
By Tetsuichi Nomura, Mamoru Yoshimizu, Takahisa Kimura
Fisheries Research, Volume 17, Issues 1-2, Pathological Conditions of Wild Salmonids, June 1993, Pages 137-146, ISSN 0165-7836, DOI: 10.1016/0165-7836(93)90013-W.
The distribution and incidence of Aeromonas salmonicida in mature chum salmon (Oncorhynchus keta), pink salmon (Oncorhynchus gorbuscha), and masu salmon (Oncorhynchus masou) in Japan, all of which showed no apparent clinical signs of furunculosis, was investigated from September 1979 to November 1991. A total of 17 909 chum, pink and masu salmon was collected from 37 rivers in the northern part of Japan. Aeromonas salmonicida was distributed widely in these populations of salmonids. A changing pattern of the annual incidence of A. salmonicida in salmon was observed: the incidence of A. salmonicida increased until the middle of October and decreased thereafter. The agent could not be isolated from immature fish. Aeromonas salmonicida was also isolated from the ovarian fluids of fish showing no apparent clinical signs of furunculosis. We concluded that the A. salmonicida carrier state in mature fish may pose a serious problem in the prevention of furunculosis.