The elimination of a debilitating, degenerative skin disease in horses is now possible, thanks to the recent identification of a gene mutation and development of a new diagnostic test by UC Davis researchers.

Findings from the study on the genetic cause of hereditary equine regional dermal asthenia, or HERDA, which primarily affects the American quarterhorse breed, were reported online May 8 in the scientific journal Genomics by veterinary geneticist Danika Bannasch and colleagues at the School of Veterinary Medicine. A patent on the test is pending.

"Identification of the gene enabled us to develop a DNA screening test to help horse breeders avoid producing horses with this disease," Bannasch said.

"Equally important, the test should prevent the unnecessary destruction of young horses that actually have less serious skin irregularities, which can be mistaken for the early stages of HERDA."

The research represents the first time that a scan of the whole horse genome has been used to identify a novel disease gene in the horse. These findings were presented to the horse genomics community at the Plant and Animal Genome XV Conference in January by Rob Tryon, the graduate student working on the project. Stephen White, a professor of veterinary dermatology at UC Davis, led the clinical investigations of HERDA.

In horses with the disease, the skin along the saddle area of the horse's back can stretch and tear easily, making the horse unfit for riding. Researchers suspect that the disease may be related to a deficiency in the horse's wound healing process or a malfunction in its normal inflammatory response system.

An earlier study of affected horses by the UC Davis group demonstrated that the disease cannot be definitively diagnosed by skin biopsy. Foals affected by the disease rarely show symptoms at birth, and most cases are not diagnosed until the horse is about 2 years old and being broke to ride.

Previous work by the UC Davis group showed that the disease has an autosomal recessive mode of inheritance and carriers show no signs of the disease.