Anhidrotic Horses -- New, More Accurate Risk Factors Found

Nearly 5,000 horses from 500 different farms helped identify anhidrosis factors for University of Florida researchers. Geography, breed, and use of horse were examined to determine factors for anhidrosis--the lack or decreased production of sweat.

While it is widely known that some horses lose the ability to sweat properly in hot, humid climates like Florida, accurate information about the true prevalence of the condition and which horses are at risk is lacking.

"Since the studies performed to date are small and did not used objective research methods, the purpose of this study was to get a better estimate of the prevalence of anhidrosis and to identify factors at the farm and animal level that are associated with this condition," explained Robert MacKay, BVSc, PhD, Dipl. ACVIM, and Jorge Hernandez, DVM, MPVM, PhD, lead researchers on the study.

Questionnaires were distributed to 1,207 horse farms throughout Florida in the year 2005. Of these, 500 farms completed the questionnaires. Hernandez et al. found that:

  • 11.2% of study horses in Florida were anhidrotic;
  • More operations in southern Florida (26.5%) had a horse with anhidrosis than was the case in central (13.4%) and northern (5.3%) Florida;
  • Show and riding horses were 5 and 15 times more likely to have anhidrosis than horses on ranch operations;
  • Thoroughbreds, warmbloods, and horses with a family history of anhidrosis were more likely to be affected; and,
  • Horses that foaled in the west or midwestern region of the U.S. were at higher risk of becoming anhidrotic if moved to Florida.

"Horses with a family history of anhidrosis should be examined by a veterinarian for diagnosis of this condition before they are exposed to exercise in a hot and humid climate," said Hernandez et al. "Horses with anhidrosis require medical management and reduced workload or even removal from physical activity. Anhidrotic horses forced to perform can suffer severe consequences, including multiple organ failure in response to hyperthermia or even death."

The study, "An epidemiologic study of anhidrosis in horses in Florida," was published in the May 15, 2010, edition of the Journal of the American Veterinary Medical Association. Eric Johnson, MS also contributed to this work.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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