Resistance To Walleye Dermal Sarcoma Tumor Redevelopment     R. G. Getchell, G. A. Wooster, and P. R. Bowser   Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA     Abstract. -- Walleyes (Stizostedionvitreum) infected with walleye dermal sarcoma (WDS) virus were rechallenged in two separate trials.  Walleyes were re-challenged with a topical application of a cell-free dermal sarcoma tumor filtrate applied to the opposite side of the fish from the original inoculation site and were allowed to develop grossly visible tumors at 15°C for 5 months.  The rate of tumor redevelopment (calculated as incidence density) was compared with naive fish that received the same inoculum.  The incidence of tumor redevelopment was significantly lower in walleyes that had previously been challenged and infected with WDS virus.  This resistance to walleye dermal sarcoma recurrence helps explain the epidemiology of WDS seen in the wild.