Attenuated fish vaccine following culture in iron limited media

A method, comprising:

• providing a fish vaccine comprising a live attenuated derivative strain of a bacterium grown in or on a medium that is iron-limited from a live attenuated primary strain of the bacterium which had been grown in or on a medium that is not iron-limited;
• and
• administering the fish vaccine to fish to reduce morbidity and/or mortality due to disease caused by exposure of the fish to a live non-attenuated pathogenic strain of the bacterium.

A method for reducing morbidity and/or mortality of salmonids due to coldwater disease caused by Flavobacterium psychrophilum, comprising:

• providing a fish vaccine comprising a live, attenuated strain of a Flavobacterium psychrophilum designated 259-93.B. 17, deposited with ATCC under the accession number PTA 9205, that is grown in or on iron-limited media;
• and
• administering the fish vaccine to salmonids to reduce mortality and/or morbidity in the salmonids due to coldwater disease caused by a live, non-attenuated pathogenic strain of Flavobacterium psychrophilum relative to mortality and/or morbidity in salmonid fish that have not been administered the fish vaccine and are exposed to the live, non-attenuated pathogenic strain of Flavobacterium psychrophilum.

A method, comprising immersing salmonids in water that contains an effective amount of a live, attenuated strain of Flavobacterium psychrophilum grown in or on iron-limited media, thereby increasing a survival rate of the salmonids relative to a survival rate of salmonids that are not immersed in the water and are exposed to a live strain of a bacterium that is not grown in or on iron-limited media.