Warmblood Fragile Foal Syndrome (WFFS)

Description

Warmblood Fragile Foal Syndrome (WFFS) is an inherited autosomal disorder caused by a single mutation in PLOD1 gene. The PLOD1 gene codes for an enzyme that enables collagen fiber growth. These collagen fibers support the strength of many tissues. Mutations in PLOD1 are known to cause a similar disorder in humans known as Ehlers-Danlos Syndrome VI (EDSVI). Dr. Winand discovered the mutation in the PLOD1 gene that causes this disorder in certain horse breeds.

WFFS has been identified in a population of horses known as Warmbloods. A “warm-blooded” horse describes its temperament, rather than the scientific association of warm-blooded mammals vs. cold-blooded reptiles.

Primarily originating in Europe during the Middle Ages, Warmblood horses were the result of breeding large, cold-blooded draft horses of northern Europe with hot-blooded, lighter, and faster Arabian horses that warriors captured in the Middle East and Africa. As a result, Warmbloods are a group of mid-sized horse types often called Sport Horses. They were developed with the aim of competing in Olympic equestrian sports. The frequency of the mutant gene in Warmbloods appears to be approximately 6.40%.

An affected WFFS foal is born with two copies of the mutated gene, one coming from each parent. The affected foal will display extreme skin fragility characterized by tearing, ulceration, etc. from contact with normal surroundings. Small skin lesions can occur anywhere on the body, but are especially noted on pressure points. In addition to skin wounds, lesions may also be found on the gums and other oral cavities and mucous membranes. The limb’s joints are lax and hyper-extensible. Fetlocks are the most dramatically affected, which generally prevents a foal from standing normally.

Unfortunately, there is no cure for WFFS and all affected foals must be euthanized soon after birth to preserve quality of life. As the condition worsens, the foal will begin to develop severe infections. They will also suffer from increasing pain and discomfort. Foals often die from these infections, or are euthanized within 3-8 days after birth.

WFFS is an autosomal recessive trait, which means that two copies of the disease from the parents are required in order to present symptoms of WFFS. A horse with only one copy of the disease is known as a carrier and does not present symptoms of WFFS. When breeding two carriers together, there is a 25% chance per foal born that they will develop symptoms of WFFS. There is a 50% chance per foal born that they will also become carriers of WFFS. This makes DNA testing a valuable tool in order to lessen the chance of having a horse born with WFFS.