open access

https://hdl.handle.net/2115/39004

The Epidemiological Study of Furunculosis in Salmon Propagation

英語

1992-10

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service

Control of disease in aquaculture : proceedings of the nineteenth U.S.-Japan meeting on aquaculture, Ise, Mie Prefecture, Japan 29-30 October, 1990, satellite symposium: 2 November

101-108

Nineteenth U.S.-Japan Meeting on Aquaculture. 29-30 October and 2 November 1990. Ise, Japan.

The authors attempted to determine the distribution and prevalence of Aeromonas salmonicida in mature chum (Oncorhynchus keta), pink (O. gorbuscha), and masu salmon (O. masou) in Hokkaido that showed no apparent clinical signs of furunculosis. From September 1979 to November 1989, a total of 12,891 chum, pink, and masu salmon were collected from 30 rivers. The changing pattern of the annual prevalence of A. salmonicida in salmon was closely related to changes in fish density in the holding ponds: the prevalence of A. salmonicida increased in proportion to the increase in the number of fish in the ponds. We concluded from the results of histological and bacteriological examinations that fish with A. salmonicida in the kidney were not diseased but were carriers of A. salmonicida. The agent could not be isolated from the immature fish examined. A. salmonicida was also isolated from the ovarian fluid of fish showing no apparent clinical sign of furunculosis. Few A. salmonicida were found on the surface of the eggs one hour after fertilization. A survey of agglutination titers against A. salmonicida in sera of chum, pink, and masu salmon showed great variability within the species. The isolated strains were identified as A. salmonicida subsp. salmonicida and were pathogenic to salmonids. We concluded that the A. salmonicida carrier state in fish poses a serious problem in the prevention of furunculosis and its reduction plays a key role in salmon propagation. Both maturation of fish under conditions of low density in ponds, and disinfection of their eggs, are necessary to prevent fish furunculosis during artificial propagation of salmon.

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