Unusual Spots

Our mare has suddenly developed white spots all over her body with no apparent cause. What would cause this?

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Q. Our 11-year-old chestnut Morgan mare has suddenly developed white spots all over her body with no apparent cause. She is outside 24/7. The spots range in size from about dime-size all the way up to silver dollar size. There doesn’t seem to be any irritation or irregularity in the skin. It looks like someone splattered her with white paint. Are there any clues as to the cause?

J.M. Hawks, via e-mail

A. It sounds like your horse is exhibiting a form of vitiligo (also called leukoderma or birdcatcher spots), an uncommon acquired pigmentation disorder characterized by progressive areas of pigment loss. These spots typically are only a cosmetic problem and rarely indicate other problems. There is also no known cause or effective treatment. Veterinarians have seen a higher incidence of vitiligo in some breeds (for instance, Arabians) than others, suggesting there might be a genetic basis.

White hair color can also be associated with trauma such as healed wounds or saddle sores from improperly fitting tack, but this does not sound like the case with your horse. Other causes for vitiligo can include skin damage due to sunburn, sun damage, frostbite, and even infections with the parasite Onchocerca. If you are still concerned about these spots I would recommend talking to your veterinarian about them during your next exam

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Written by:

Kristen Slater, DVM, practices with Kasper & Rigby Veterinary Associates in Magnolia, Texas. Her practice interests include preventive medicine, reproduction, sports rehabilitation, and conditioning.

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