Identification Of A Novel Piscine Retrovirus Associated With An Outbreak Of Swimbladder Sarcoma In Atlantic Salmon, Salmo salar     Claudia A Sutton1, Sandra L Quackenbush2, Paul R Bowser1,Joel Rovnak2, Rufina Casey1, James W Casey1   1Cornell University, Department of Microbiology and Immunology, Ithaca NY; 2University of Kansas, Department of Molecular Biosciences, Lawrence KS     An outbreak of salmon swim bladder sarcoma in Atlantic salmon at the North Attleboro National Fish Hatchery occurred in 1997-8.  Affected fish were juveniles caught in the Pleasant River, ME as part of the New England salmon restoration project. Besides mortality due to swim bladder sarcoma, involved fish performed poorly, and did not attain sexual maturity. Our laboratory identified retroviral pol sequences in the tumors by degenerate PCR; the pol amplicon was also detected in blood DNA from this fish population. The same amplicon was also detected in blood from other Maine river-specific salmon broodstock, as well as in broodstock from a commercial facility. We have now deduced the entire proviral sequence of the retrovirus implicated in the swim bladder sarcoma outbreak, which we have named SSSV-1. We have recently succeeded in transmission of the virus to salmon in the lab using swim bladder tumor filtrate. In the course of the transmission studies, we discovered that the recipient salmon, from the New York Adirondack hatchery, which were negative for the SSSV-1 pol amplicon, were infected with a second, highly related virus we call SSSV-2. More recently, a third highly related virus has been detected in a wild Maine salmon. We hypothesize that there are several SSSVs existing in the wild, and that infection of fish with these viruses have negative consequences on fish viability.