Hereditary equine regional dermal asthenia (HERDA)
Photo credit: Dannika Bannasch, UC Davis
Hereditary equine regional dermal asthenia (HERDA) is a genetic skin disease found in the Quarter Horse. The disease is characterized by hyperextensible, elastic skin, severe dermatologic lesions, and often scarring along the back and withers of affected horses. Horses usually present between 1-3 years of age, often when the horse is first being introduced to a saddle.
There is no cure or effective treatment, and these individuals are unusable as performance animals, therefore the majority of diagnosed horses are euthanized.
HERDA is inherited in a recessive fashion (two copies of the mutation are necessary to produce disease). A mutation in the gene which codes for a protein thought to be integral in collagen folding is present in horses with HERDA. Screening of the general Quarter Horse population resulted in an estimated 3.5% carrier frequency.
A genetic test is now available for HERDA that can identify normal, affected, and carrier individuals. Information about this test, as well as submission information and pricing is available through the Veterinary Genetics Laboratory at the University of California, Davis.
Breeders should be encouraged to test and identify carriers of HERDA to reduce further propagation of this genetic mutation in the Quarter Horse population.