Equine Alopecia Areata

Researchers at UC Davis have now described this skin disease in horses
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Researchers at UC Davis have now described this skin disease in horses
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Equine Alopecia Areata Credit: G. Miller

In 2008, a client of mine headed to Kentucky and came home with a trailer load of horses for resale. One of them, an older mare named “Sugar Babe,” appeared to have a ringworm infection. She had round, raised welts over most of her body, including her face. Despite a dozen different types of treatment, we could never get it to fully resolve. It seemed to just “come and go” on its own, despite all of our efforts to treat it both systemically and topically.

Another client, who enjoys dressage, has dealt with a similar problem in her 22-year-old gelding for several years. Every winter, he developed large round lesions of lost hair that would scab and sometimes bleed, but then slowly disappear. No medication seemed to work on them, which would drive the owner crazy!

Both horses made their way to the U.C. Davis Veterinary Medical Teaching Hospital in Davis, Calif., where they were examined by the dermatology service. In the end of it all, they were diagnosed with a disease called Equine Alopecia Areata. This disease causes hair loss due to inflammatory changes within and around hair bulbs and lower portions of the hair follicles. Although it can look grizzly, it is thought to be more of a cosmetic problem than a serious medical condition.

Equine Alopecia Areata causes hair loss.

Equine Alopecia Areata causes hair loss.

Alopecia areata in general has been known to occur in other species including dogs, cats, cattle, mice, chickens and humans. Until now, it had not been described officially in horses. Alopecia areata is an auto-immune disease in which the body produces antibodies to the base of the hair follicle. The antibodies then attack the hair follicle causing it to break off at the base. The antibodies will often prevent regrowth of the hair follicle for several weeks.

The disease is diagnosed by both visual assessment and by taking skin biopsy samples and then examining them under a microscope. At this point, immuno-suppressive treatment is not recommended since the condition is cosmetic. In other words, it does not appear to be hurting the horse enough to risk the potential side effects of immune suppression. For horses that have light to white skin, a zinc-based sunscreen can be helpful to reduce secondary sunburn as a result of exposure.