Lethal White Overo Syndrome

This disease is fatal, and cannot be cured or adequately treated and is expected to result in the death of the horse.

Lethal White Overo Syndrome (LWO) is a genetic disorder primarily affecting horses, particularly those of the American Paint Horse breed, although it can occur in other breeds as well. It is caused by a mutation in the endothelin receptor B (EDNRB) gene, resulting in a lack of certain nerve cells in the gastrointestinal tract. As a consequence, affected foals are born with a non-functional colon, leading to severe intestinal obstructions and ultimately death within a few days of birth.

LWO is characterized by a distinctive white coat color pattern, often with a predominantly white body and dark-colored patches. Due to its lethal nature, responsible breeding practices and genetic testing are crucial in preventing the spread of this devastating syndrome within equine populations.

Symptoms

Exclusively found in

Treatment

There is currently no cure for Lethal White Overo Syndrome (LWO) in horses. The condition is caused by a genetic mutation that is present at birth, and the foals are typically born without colon and/or rectal tissue, which is not surgically fixable. Treatment options for foals with LWO are primarily focused on supportive care to help manage symptoms and pain. If the foal is in discomfort, humane euthanasia should be prioritised.

Prevention

LWO is a serious and lethal disease, and the best way to prevent it is to avoid breeding two horses that are carriers of the EDNRB mutation.

Genetic testing is available to determine whether a horse is a carrier of the LWO mutation. By avoiding breeding two carriers together, it’s possible to eliminate the risk of producing foals affected by LWO.