TWENTY-SECOND ANNUAL EASTERN FISH HEALTH WORKSHOP ROYAL PAVILLION RESORT, ATLANTIC BEACH, NC MARCH 18 - 20, 1997 Case study on development of oxytetracycline resistant Aeromonas salmonicida among sea run Atlantic salmon Patricia Barbash1 and Rocco C. Cipriano2 1US Fish and Wildlife Service, Fish Health Unit, PO Box 155, Lamar, PA 16848; 2USGS/Biological Resources Division, National Fish Health Research Laboratory, 1700 Leetown Road, Kearneysville, WV 25430 Each spring, sea-run Atlantic salmon (Salmo salar) return to the Connecticut River and are captured at the Holyoke Dam (Holyoke, MA). Fish are transported to the Richard Cronin National Salmon Station (Sunderland, MA) until they are spawned in the following fall. Once these fish begin their return migration, they no longer accept food. Hence, they become extremely susceptible to infection and disease exacerbated by culture conditions within holding facilities. Furunculosis, causes acute mortality during this period of captivity. Such mortality necessitated development of an effective immunoprophylactic protocol in which sea-run fish are injected intraperitoneally with 2.4 mg of oxolinic acid plus 0.5 mL of Aeromonas salmonicida / Yersinia ruckeri bacterin per kg of body weight. In 1995, the Food and Drug Administration voided the Investigational New Animal Drug permit for ocxolinic acid and oxytetracycline was used instead. In October 1996, a furunculosis epizootic, caused by an oxytetracycline-resistant Aeromonas salmonicida occurred among Atlantic salmon held at the Richard Cronin National Salmon Station. The disease impacted production of gametes and failure to curtail such infection in future spawning cycles could jeopardize the restoration effort. This report discusses the nature of that epizootic and emphasizes the need for an effective antibiotic. Return to 22nd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page