Resistance to Walleye Dermal Sarcoma Tumor Redevelopment

Walleyes Stizostedion vitreum infected with walleye dermal sarcoma (WDS) virus were rechallenged in two separate trials. Walleyes were rechallenged with a topical application of a cell‐free dermal sarcoma tumor filtrate applied to the side of the fish not originally inoculated; these fish 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 in the wild.