TWENTY-FIFTH ANNUAL EASTERN FISH HEALTH WORKSHOP MARCH 10-13, 2000   Swim Bladder Sarcoma In Atlantic Salmon In The United States And An Associated Retrovirus        Paul R. Bowser1, J. W. Casey1, S. L. Quackenbush1, R. N. Casey1, J. A. Coll2, R. C. Cipriano3 and L. Lofton4   1Department of Microbiology and Immunology, College of Veterinary Medicine,Cornell University, Ithaca, NY 14853-6401; 2Northeast Fisheries Center, U.S. Fish and Wildlife Service, Lamar, PA 16848; 3National Fish Health Research Laboratory, U.S. Geological Survey, 1700 Leetown Road, Kearneysville, WV 25430; 4U.S. Fish and Wildlife Service, National Fish Hatchery, North Attleboro, MA 02760                   A population of adult Atlantic salmon (Salmo salar) held at the North Attleboro National Fish Hatchery (NANFH) were experiencing chronic mortalities.  The fish were captured from the Pleasant River, ME and held at the hatchery for use as brood fish.  Progeny from these fish were to be used to augment the Atlantic salmon population of the Pleasant River, one of six rivers designated for this program.  Moribund Atlantic salmon exhibited external signs that included swollen abdomen, as well as multifocal hemorrhage on the body and fins.  Affected fish may also exhibit signs of lethargy and poor growth. Upon necropsy, some fish had multinodular masses of the swim bladder.  In advanced cases, these multinodular masses replaced the entire swim bladder and displaced the internal organs, resulting in a distended abdomen.  Upon histological examination, the tumors were observed to be made up of well-differentiated fibroblastic cells that are arranged in interlacing bundles.  A similar outbreak of swim bladder fibrosarcoma occurred in cage-cultured Atlantic salmon in Scotland in 1976.  Preliminary molecular characterization of the virus genome indicated that, within the Family Retroviridae, the Salmon Swim Bladder Sarcoma virus (SSSV)  is distinct from the other known fish retroviruses : Walleye Dermal Sarcoma Virus (WDSV), Walleye Discrete  Epidermal Hyperplasia Virus-1 and -2 (WEH1, WEH2), and Perch Epidermal Hyperplasia Virus (PEHV).  A PCR diagnostic test was developed to detect proviral DNA (POL region) of SSSV in blood samples.  A limited number of the fish were placed in an isolation facility for monitoring on a seasonal basis.  Preliminary results suggest that there may be a seasonality associated with viral production; with the greatest amount of virus being present in the late fall.   Return to 25th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page