Walleye epidermal hyperplasia virus

The walleye epidermal hyperplasia viruses are two species of retroviruses classified under Epsilonretrovirus, a genus in the family of Retroviridae. There are three genome sequenced and identified exogenous retroviruses of this genus which include two known types (WEHV-1 and WEHV-2) associated with walleye epidermal hyperplasia disease. Both viral types are confirmed to be the causative agents of the neoplastic condition in the freshwater fish species, the North American walleye (Sander vitreus). The specific association of retroviral infection with proliferative lesions in fish is based on the presence of retrovirus-like particles (observed via electron microscopy) and reverse transcriptase activity (using reverse transcriptase polymerase chain reaction techniques) from neoplastic tissue. Although both virus types have been observed in lesions of diseased fish, each cell of the infected tissue is host to a specific virus. Transmission studies have also shown that WEHV-2 has been the more proliferative agent of the condition as compared to WEHV-1.