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Q: My horse Leo develops an unusual coat pattern over his whole body every summer. The length and texture of the hairs are all about the same, but the hairs grow in different directions. His winter coat appears to be normal, and after he sheds out, I don’t really notice the pattern until the end of June. Once it reappears, the pattern is fairly similar each year, although it does change a bit.
Leo is 13 now, and his coat has done this every year since I got him when he was 8. He is healthy and sound, with no prior injuries that we know of. He is not itchy, and he has no lesions, no sensitivities to insects, no hives. My veterinarian has never seen this coat pattern, but she found no problems when she examined him about a month ago, and she did not seem alarmed. What might be causing this? Is it anything to worry about?
A: Your horse appears to have whorls---patches of hair that lie in the wrong direction. These are not unusual, although your horse’s case is extreme. These odd whorls and varying directions of hair growth do pop up from time to time--I have seen one other horse with odd
whorls to this extent. In some cultures these sorts of patterns are carefully noted and serve as the basis for individual horse identification.
Chances are, the pattern is there year-round, but maybe it’s less noticeable in his winter coat---the longer hairs may be more inclined to lie as they are brushed despite the underlying whorls. As long as he is healthy, this is perfectly normal---for him. D. Phillip Sponenberg, DVM, PhD,
ACT (Honorary) Virginia–Maryland College of
Veterinary Medicine Blacksburg, Virginia
A: I recall seeing a horse with a similar bizarre pattern about 15 years ago, but without follow-up.
The question of “Is it anything to worry about” is probably dependent on the age of the horse. This horse is on the young side for a diagnosis of PPID (pituitary pars intermedia dysfunction, also called Cushing’s disease), but this disease has been diagnosed in horses as young as 7 years old.
This case would be the antithesis of a horse with PPID---which is typically characterized by a long hair coat that does not shed out. But it might be worth running a diagnostic test anyway just to rule it out. The reason I say this is that I know of a donkey that became almost totally hairless (also the antithesis of PPID) but grew its hair back after it was started on pergolide.
If you wanted to pursue further tests, it might be interesting to take skin biopsies from both the affected and unaffected areas, although I am not certain this would lead us to a diagnosis. Stephen D. White, DVM, DACVD University of California–Davis Davis, California
HAIRY SITUATION: These photos, taken in spring, summer and winter, show the unusual coat pattern that Leo develops each year. The 13-year-old gelding is healthy and sound and has no known allergies or past injuries.
LOOKING FOR CLUES: Leo’s owner describes the area in question as being similar to other parts of the coat but “the hairs grow in different directions.”