Epidermal tumors of rainbow smelt with associated virus.

Epithelial tumors of the skin occurred in landlocked populations of rainbow smelt (Osmerus mordax) in several lakes in New Hampshire (USA) during the spawning runs. Histologically, these were noninvasive epithelial cell lesions. Herpesvirus-like particles could be seen in the nucleus and cytoplasm. The lesions occurred in both males and females. Prevalence, which varied annually, was as high as 30%.