Deafness in American Paint Horses Examined

Deafness in American Paint Horses Examined

American Paint Horses with certain coat patterns and blue eyes appear to be at particular risk for deafness.


American Paint Horses with certain coat patterns and blue eyes appear to be at particular risk for deafness, reported researchers from the School of Veterinary Medicine, University of California-Davis.

"Deafness is infrequently recognized in horses. While there are a variety of mechanisms by which a horse can become deaf, there is little information regarding the possibility that a genetic mutation that causes spotted coat colors may also result in hearing impairment," explained study co-author K. Gary Magdesian, DVM, Dipl. ACVIM, ACVECC (emergency and critical care).

Genetic mutations that cause specific coat colors and hearing impairment have been identified in dogs, cats, and other species.

"To investigate whether coat color patterns were associated with deafness in American Paint Horses, we compared clinical findings, hearing test results (a brain auditory-evoked response test), and genotype of the endothelin B receptor gene (linked to a specific overo coat pattern) in both confirmed and suspected deaf American Paint Horses and nondeaf American Paint Horses and Pintos," relayed Magdesian.

Key findings in this study were that:

  • All 14 deaf American Paint Horses had abnormal brain auditory-evoked response tests;
  • All nondeaf horses had normal brain auditory-evoked response tests;
  • Most but not all deaf American Paint Horses had splashed white or splashed white-frame blend coat patterns;
  • Other coat patterns noted in deaf horses included frame overo and tovero;
  • Extensive head and limb white markings were observed in deaf horses;
  • Most deaf horses had two blue eyes;
  • Most deaf and suspected deaf horses (31 out of 34, or 91%) had the endothelin B receptor gene mutation, and
  • Deaf and suspected deaf horses could be used successfully in performance events.

"This study is important for owners and veterinarians to be aware that some American Paint Horses are more at risk for deafness than others and should be considered when performing prepurchase examinations, when handling deaf horses, and the potential for passing this trait on to offspring," concluded Magdesian.

The study, "Evaluation of deafness in American Paint Horses by phenotype, brainstem auditory-evoked responses, and endothelin receptor B genotype," was published in the November 15, 2009, edition of the Journal of the American Veterinary Medical Association. The abstract is currently available on PubMed.

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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