Enzootic nasal tumor virus
The enzootic nasal tumor virus of the betaretrovirus genus is a carcinogenic retrovirus that causes enzootic nasal adenocarcinoma in sheep and goats. Strain ENTV-1 is found in sheep and strain ENTV-2 is found in goats.
Source: Wikipedia — Enzootic nasal tumor virus (CC BY-SA 4.0)