Rare Horse Diseases

The old saying, "healthy as a horse" is a false one. Horses are prone to many ailments mostly due to domestication, whether as a result of poor breeding practices or from not being able to fully adapt to standing in a stall many hours a day. As a result, horses are susceptible to many diseases, some of them rare.

  1. Lethal White Foal Syndrome

    • A kind of color pattern exists in Paint horses called overo, where white splotches start from the belly and go up. However, if two overo-patterned Paint horses are bred, the resulting foal is pure white. The foal usually dies in 24 hours due to lethal white foal syndrome, which means it cannot digest food. This is thought to be a genetic disease linked to the overo coat pattern, but can also be carried by Paints with other coat patterns and has now been found in some Quarter Horses, Thoroughbreds, mustangs and miniature horses, so all breed stock need to be tested to see if they carry the gene.

    Sudden Death Syndrome

    • This mysterious heart disease only affects Thoroughbreds or horses with a large percentage of Thoroughbred in them. For an unknown reason, a perfectly healthy horse within an hour after a workout, drops dead. Necropsies show the heart has suffered numerous small lesions. The most famous racehorses who have died from this are 1984 Kentucky Derby winner Swale and 1992 Santa Anita Handicap winner Best Pal.

    Tyzzer's Disease

    • This often fatal liver disease caused by a bacteria called occurs in a variety of mammals, including horses. It shows up in foals that are between nine days and six weeks old. Symptoms differ from foal to foal. Some will just drop dead while others will linger, seem depressed and have a yellow tint to the whites of their eyes. It can be contagious to other foals, cats, rabbits and rodents. Just how Tyzzer's operates is unknown.

    Equine Piroplasmosis

    • This is a very rare, sometimes fatal disease caused by two parasitic microorganisms that live in the horse's blood. It is more common in Central and South America, where ticks live. The ticks bite an infected horse and then transmit the microorganisms to another horse. Infected needles can also spread the disease. Within one to three weeks of being bitten, the horse becomes very weak, jaundiced, feverish and colicky.

    Contagious Equine Metritis

    • This is a sexually transmitted disease that is so rare, only a handful of horses get it per year. It was more common in the 1970's, but has since been reduced when it was discovered that a bacteria was the cause. It is not fatal, but can make horses infertile and harm their immunity systems.