Thrush is an infection of the frog in the foot of the horse and is usually caused by the anaerobic organism Fusobacterium necrophorum. The frog has two distinct layers, the external skin, known as the horn tissue, and the corresponding vascular layer of tissue, called the sensitive corium.
Horse drinking from a pool of stagnant water with front hooves in mud.
Stalls and pastures with an environment contaminated by urine and acidic manure are breeding grounds for thrush bacteria affecting horses' feet.
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Beneath the inner sensitive layer is a pad-like shock absorber, called the deep digital cushion, that reduces concussion for the horse's hoof and the entire limb. A hoof that is infected with thrush will exhibit soreness and contain black, pus-like liquid. Some bleeding may occur, and a strong, foul odor is emitted by the infected area.
Although thrush often strikes during wet, rainy, spring seasons, it appears year-round when the horse's environment is wet, muddy, and contaminated by bacteria. Thrush is caused by anaerobic bacteria and usually affects horses that live in wet conditions.
Stalls and pastures with an environment contaminated by urine and acidic manure are breeding grounds for the thrush bacteria. The infection is accelerated by lack of proper hoof hygiene. Although thrush is a somewhat common condition, it shouldn’t be underestimated. If left untreated, it may penetrate the sensitive structures of the hoof and cause temporary to permanent lameness.
To prevent thrush, the best offense is a good defense. In other words, prevention and proactive farm management is crucial. The best control for thrush is proper sanitation, especially where your horses will be spending large amounts of their time. Proper care of the horse's hoofs is the best prevention of thrush. Horses that are kept in stalls with clean, dry shavings and have their feet thoroughly picked on a regular basis very seldom develop thrush.
Treatment of thrush is best done by a farrier or veterinarian, although commercial treatments are available so owners and handlers can treat the disease. The horse should be moved to a clean, dry area, and antiseptic foot wash used to clean the hoofs. The hoofs, particularly the frog area, should be thoroughly cleaned and trimmed. This will help aerate the frog area, and the effectiveness of medication applied to the affected areas will be maximized.
Once cleaned and medicated, the hooves should heal within six to seven days if the horse is kept in clean, dry conditions.