The development of equine sarcoids following latent bovine paillomavirus infection will be studied as well as variations in DNA sequence. Latent equine paillomavirus infections in the horse population and the evolution of EcPV-2 latency towards squamous cell carcinomas will be studied. The papillomavirus responsible for aural plaques will be characterized and the horse population will be screened for the presence of new papillomaviruses.