2 CLOSELY-RELATED BUT DISTINCT RETROVIRUSES ARE ASSOCIATED WITH WALLEYE DISCRETE EPIDERMAL HYPERPLASIA

Walleye discrete epidermal hyperplasia (WEH) is a hyperproliferative s kin disease that is prevalent on adult walleye fish throughout North A merica. We have identified two retroviruses associated with WEH, desig nated here as walleye epidermal hyperplasia virus type 1 and type 2 (W EHV1 and WEHV2), that are closely related to one another (77% identity ) and to walleye dermal sarcoma virus (64% identity) within the polyme rase region. WEHV1 and/or WEHV2 viral DNA was readily detected by PCR in hyperplastic tissue samples, but only low levels of viral DNA were detected in uninvolved skin. Southern blot analysis showed one to thre e copies of integrated WEHV2 viral DNA in lesions but did not detect W EHV2 viral DNA in uninvolved skin from the same fish. Northern blots d etected abundant levels of WEHV1 and/or WEHV2 virion RNA transcripts o f approximately 13 kb in hyperplastic tissue, but virion RNA was not o bserved in uninvolved skin and muscle. These results suggest that WEHV 1 and WEHV2 are the causative agents of discrete epidermal hyperplasia .