INVASIVE WALLEYE DERMAL SARCOMA IN LABORATORY-MAINTAINED WALLEYES STIZOSTEDION-VITREUM

Walleye dermal sarcoma (WDS) was first described as a multifocal cutan eous neoplasm of walleyes Stizostedion vitreum in Oneida Lake, New Yor k, USA. The neoplasm was subsequently shown to be caused by a type C r etrovirus. We have successfully transmitted the neoplasm in laboratory -maintained young-of-the-year (YOY) walleyes in a number of pathogenes is studies over the past 6 yr. Neoplasms in these laboratory trials we re typical of those superficial neoplasms observed in adult feral wall eyes. A transmission study was begun summer 1994 using 9 wk old walley es. Starting at 56 d and continuing throughout the experiment, injecte d fish developed grossly visible, multiple small white skin masses tha t varied from 0.5 to 10 mm in diameter. These masses appeared on the s kin of the head, back, flank, fins and lips. Histopathological examina tion revealed that some of these neoplasms, especially those collected at 84 d and beyond, did not remain cutaneous, but were locally invasi ve and replaced normal tissue, primarily muscle. One neoplasm on the h ead of a young walleye had deformed the brain and had invaded the skul l. Due to the unusual invasive nature of the microscopic lesions of th e neoplasm, these findings are reported.