Thrush Common, Yet Serious, But Treatable Hoof Ailment In Horses

Two horses went lame in the same day; one in a clean dry barn, and other deep in mud.

What in the world is wrong? Farrier quickly diagnosed the seemingly serious dilemma.

“They have thrush,” the farrier said simply.

What is thrush?

“Thrush is a very common bacterial infection that occurs in the hoof of a horse specifically in the region of the frog,” according to Dr. Tia Nelson, practicing veterin­arian who’s also a professional farrier.

What’s the frog?

“The frog is a part of the hoof, located on the underside, which should touch the ground if the horse is standing on soft footing,” Nelson defined.

“It is triangular in shape, and extends midway from the heels toward the toe, covering around 25 percent of the bottom of the hoof,” the veterinarian clarified.

Bacteria causing thrush is said to occur naturally, especially in wet, muddy, or unsanitary conditions, such as an unclean stall.

“It grows best with low oxygen,” Nelson said.

“Horses with deep clefts or narrow heels are more at risk of developing thrush,” she added.

“Healthy feet rarely develop thrush. Good circulation to the foot helps keep it healthy. If the foot is out of balance or has contracted heels, or if lameness keeps the horse from using the foot normally, that raises the risk for thrush.

“I’ve seen thrush in dry, arid places where you would never expect it in feet that were not healthy,” Nelson said.

The most obvious sign of thrush is usually the odor that occurs when picking out the feet.  Additionally, the infected areas of the hoof will be black in color and will easily break or crumble when scraped with a hoof pick.

If thrush is long-standing and deep, the horse will flinch when his feet are cleaned or trimmed. In severe cases there may be a discharge from the frog.

Recommended treatment for thrush begins with cleaning the horse hoof thoroughly and having the farrier trim the frog.

“The horse will be lame, with swelling above the hoof due to infection in the foot. A neglected case can eventually affect the inner tissues, including the navicular joint,” according to the veterinarian.

Actually, many horses can have thrush and not be lame. ”However, if left untreated the bacteria may migrate deeper into the sensitive parts of the hoof, resulting in more severe lameness,” Nelson verified.

In earlier times, before people knew about bacteria, horsemen thought thrush was caused by secretions from the frog itself that collected in the clefts, making the frog moist and foul.

Now it’s known that this “hoof rot” is caused by bacteria commonly found in barnyards and pastures. They thrive in wet, decaying material, such as bedding and manure in dirty stalls, or in wet pens and paddocks.

Several pathogens cause thrush, but most common is the same one that causes foot rot in cattle, diphtheria in calves, and navel ill in calves and foals.

If a horse’s feet are frequently packed with dirt, mud or manure, the lack of air next to the frog and the constant moisture in the hoof make ideal conditions for these bacteria to flourish, rotting the frog tissue. In wet conditions, there is more incidence of thrush.

“Recommended treatment begins with cleaning the hoof thoroughly, and having the farrier trim the frog,” Nelson said.

Topical medication available at most veterinary supply and tack businesses should be applied daily to a thrush-infected horse hoof.

Scrub the entire foot with a stiff brush and warm water-disinfectant. Then apply topical thrush treatment available at most veterinary supply and tack businesses.

Follow-up care should include twice-daily picking of the feet, taking special care to clean out all grooves, with regular scrubbing.

Horses with thrush, or those at risk for contracting it, are best kept in a dry, clean environment. Daily cleaning of the hooves also contributes to the prevention of thrush.

A properly trimmed frog makes the hoof’s clefts more self-cleaning. As the hoof expands and contracts with each step during exercise, this action dislodges mud and debris.

In general, thrush is relatively easy to treat, although it can easily return and it can take up to a year for a fully healthy frog to regrow after a severe infection.

Some horses are prone to thrush and have recurrent episodes no matter how clean their environment is kept. For these horses, a daily preventive swabbing can control the problem.

Better yet is continuous turnout in a clean field. Not only will these changes help clear up a case of thrush, but it will prevent its return.