Thrush Symptoms in Horses

Thrush is an infection of the hoof caused by anaerobic bacteria (bacteria that need no oxygen to thrive) or fungi. Thrush affects the central and lateral sulci (clefts) of the horse's frog and the surrounding area of the hoof. The frog is the triangular or heart-shaped spongy structure on the sole of the hoof.

  1. Causes of Thrush

    • Thrush most commonly develops in moist, muddy or unclean environments. Many bacteria and fungi contribute to the development of thrush, but as the Clyde Vet Group notes, one bacterium, fusobacterium necrophorum, is particularly known to induce thrush.

      Damp environments, however, aren't the only contributors to thrush. According to The Horse website, factors such as poor diet, abnormal hoof growth, lack of basic hoof care (shoeing, trimming, etc.), lack of exercise and poor circulation in the hoof and/or frog all predispose horses to the ailment.

    Major Symptoms

    • The first noticable symptom is typically a foul odor coming from the hoof. A black or dark-colored discharge in the affected area, specifically around the central or lateral sulci of the frog, usually accompanies the odor. Occasionally the lower limb will swell. According to the Clyde Vet Group, the hind feet are more frequently affected than the front feet. In severe cases, the infection may reach the sensitive layers of the hoof and cause pain and lameness. This lameness may become permanent if the infection is not treated promptly.

    Treatment and Prevention

    • Treatment begins by moving the horse to a clean and dry environment. Picking the debris from the hoof and scrubbing the hoof thoroughly with a stiff brush and water will clean the affected area and ready it for medication. Often, the farrier will pare down the frog to get rid of infected tissue and expose healthy tissue.

      Tack stores and farm-supply centers stock commercially available topical treatments, while some horse owners opt for homemade remedies such as sugardine (a mixture of sugar and Betadine solution) or diluted iodine. Bleach and hydrogen peroxide, which some owners use, will burn the healthy tissue and can actually retard healing.

      Stimulating the frog through exercise facilitates healing. Exercising your horse will increase blood flow to the hoof. The pressure on the frog will also flatten it, allowing the sulci to expand and generate airflow. More serious cases of thrush may require veterinary or farrier care.

      Picking your horse's feet daily, frequently exercising your horse, and carefully inspecting his hooves are all simple and effective ways to prevent thrush from ever developing.