Equid alphaherpesvirus 3, formerly Equine herpesvirus 3 (EHV-3), is a virus of the family Herpesviridae that affects horses. It causes a disease known as equine coital exanthema. The disease is spread through direct and sexual contact and possibly through flies carrying infected vaginal discharge. Signs of the disease include pustules and ulcerations of the vagina, penis, prepuce, and perineum. Lesions may also be seen on the lips and teats. Usually the only symptom seen is a decreased libido in stallions. The lesions heal within two weeks.
As with other herpes viruses, the virus remains latent in the host for life. Carrier animals can sometimes be identified by spots of pigment loss on black skin in the genital region.