Q: This past May I purchased a 4-year-old Arabian gelding in perfect health. After a few months, however, I noticed some bumps on his nose that I have never seen before, on any horse. They are pink and bubbly looking, and some of them look like little scabs. He is kept outside 24/7 and is currently separate from the other horses in case the bumps are contagious. What are these? Will they affect his health or cause him discomfort? Is there a treatment or a way to prevent them? I have attached pictures to show you what they look like. Charlene Zubrickas; Shelburne, Ontario

A:The bumps on your gelding’s nose look like typical equine papillomas (warts). What is not typical is his age. Growths like these usually occur in horses younger than 3 years old.

Papillomas are common, benign skin growths caused by a virus that is transmitted by both direct and indirect contact. The infection takes hold only in skin that has been damaged, such as by trauma, sunburn or parasites. Classical equine viral papillomas occur most commonly on the muzzle, and they usually heal spontaneously within two to three months. (Chronically affected animals should be suspected of being immunosuppressed.)

In contrast, equine ear papillomas occur in horses of all ages, most commonly on the pinnae, and they rarely, if ever, spontaneously resolve. Black flies are probably important in transmitting the papillomavirus that causes the growths, both by damaging the skin and as
mechanical vectors.

Both types of equine papillomas are visually distinctive, and further diagnostic work is rarely necessary. However, sarcoids must be considered as another potential diagnosis for any “papilloma” or “wart” that appears in an atypical site in an adult horse. A biopsy of the growths would be needed to differentiate between the two.

Papillomas do not cause discomfort, and rarely do they affect a horse’s health, so treatment is usually not necessary. For lesions that must be removed for aesthetic or health reasons, surgical excision or cryosurgery is effective. Anecdotal evidence suggests that surgical excision of some larger lesions may encourage the others to regress.

The papillomavirus is fairly stable in the environment and can survive for 63 days at 39 to 46 degrees Fahrenheit or for six hours at 98 degrees. So it is possible your gelding could transmit the virus to other horses under 3 years of age.

Steve Adair, MS, DVM, Diplomate, ACVS & ACVSMR
University of Tennessee
Knoxville, Tennessee