Junctional epidermolysis bullosa (JEB) in horses

What is JEB?

Junctional epidermolysis bullosa (JEB) is a fatal genetic disorder that causes fragile skin. Fragile skin results from a mutation in the protein that serves to anchor skin cells within the dermis. Horses must receive two copies of the mutation to develop JEB.

JEB occurs in Belgians (and related breeds) and American Saddlebreds.

Disease effects

Foals will develop skin lesions at pressure points (over bony areas) that worsen with age. The skin usually opens around the coronary band and may proceed to sloughing of the hooves.

Affected foals are also more prone to infection. If they aren’t euthanized, they’ll usually die from infection within 2 weeks.

Treatment

There is no known treatment for JEB. Foals are usually euthanized after diagnosis due to the pain associated with the disease.

Breeding considerations

Horses that carry one mutated gene are said to be JEB carriers. While they aren’t affected by the disease, they have a 50 percent chance of passing the mutated gene to their offspring.

JEB horses usually don’t make it to breeding age. Thus, JEB horses occur from crossing two JEB carriers. Testing of 8 farms revealed a 36 percent incidence of carriers among Belgians.

We recommend testing all breeding stock and avoiding interbreeding of carriers to prevent the incidence of JEB. A genetic test for JEB is available at the Veterinary Genetics Laboratory at the University of California Davis and the University of Kentucky-Gluck Equine Research Center.