Thrush in Horses: Identifying, Treating and Preventing

Thrush in Horses: Identifying, Treating and Preventing

Thrush is a bacterial and fungal infection of the frog. Learn how to spot it, treat it and prevent thrush from becoming a chronic issue for your horse.

two muddy ranch horses in a pasture (Credit: Cecilia Steel)

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The American Quarter Horse Journal

You’re picking out your horse’s hooves, expecting to find the usual mix of dirt and manure. Instead, your hoof pick produces something that looks like it crawled out of the Black Lagoon.

It’s black, it stinks … it’s unmistakably thrush.

How do I know if my horse has thrush?

Thrush is a bacterial and fungal infection of the frog. You can spot it by its foul smell and black tar-like discharge, which often ends up on the end of your hoof pick. If thrush is not treated early or the infection progresses too far, it can spread to the sensitive parts of the hoof.

John Suttle, a certified journeyman farrier with the American Farrier’s Association, says this black putty-like debris is a common infection found in the commissures of the foot (the valleys on either side of the frog, the triangular-shaped soft part of the foot) and in its central sulcus (the small groove in the middle of the frog).

What causes thrush in horses?

Thrush is often attributed to dirty, muddy conditions. Water alone won’t lead to thrush, but moisture combined with a dirty pen makes prime conditions for thrush. (Here are some tips for managing paddocks and pastures.)

While hooves kept in muck do create a perfect breeding ground for the bacteria and fungus that create thrush, John says the black gunk can also be found in horses living in immaculate conditions, or sometimes in just one hoof and not in the horse’s other three hooves.

How do you treat thrush?

The best treatment for thrush in horses is good foot care. A farrier can trim back the flaps of the frog, where infection can hide. And from there, owners should keep the foot clean – cleaning up the horse’s living conditions if necessary – and being diligent about picking out the hooves and removing the black debris. If the dirt and muck are stubborn, a wire brush or a flush with water or hydrogen peroxide can help get all of it out, John says.

Iodine (or Bleach-and-Water) Treatment

Treat thrush in horses with a germ-killing product, such as iodine or a bleach-and-water mix, diluted 50-50.

The product you use will depend on how much sensitive tissue is exposed. If, for example, you caught the thrush before it got very advanced and it’s only a superficial infection, the diluted bleach would be fine, John says. But if the thrush has spread into sensitive tissue, the bleach would be much too caustic and would burn.

Does thrush hurt a horse?

Thrush can eat its way into sensitive tissue anywhere in the frog and cause pain, either in the back part of the frog or off to its side. For this reason, you should use caution when riding a horse with thrush.

“When you use a hoof pick to clean the foot, you need to be careful,” John cautions. “Quite often, you can be rather callous with the hoof pick, and it won’t bother the horse at all. But if it does bother the horse, it may be that there’s thrush exposing that sensitive tissue. It also may be painful for the horse with narrow, upright feet who is more likely to have a closed up sulcus, with a very deep cleft that provides opportunity for moisture and germs to breed.

To clean a deep central sulcus, “you may need to use a strip of gauze-like dental floss and pull that through the deep groove,” John says. “If it’s very deep, you’ll need to get into the bottom of that, but be careful if you use your hoof pick, because that area may be very sensitive.”

Chronic Thrush

On stubborn cases of thrush, John says, “Typically you’d treat it once a day for the first week, every other day for the second week, every third day for the third week, every fourth day for the fourth week, and then leave it alone for two weeks.”

As with any hoof or health issue, if you have questions or concerns, don’t hesitate to call in your farrier or veterinarian.

Preventing Thrush

  • Daily cleaning allows you to catch any concerns early.

  • It also removes manure and other debris that can lead to thrush.

  • Be sure to thoroughly clean the sides of the frog as well as the frog itself.

  • If your horse lives in a stall, keep the bedding clean and dry to prevent thrush.

  • If your horse lives outdoors, remove manure regularly and be sure he has dry places to stand, such as a three-sided shelter with rubber mats on the ground.

John Suttle, CJF, is the former liaison between the American Farrier’s Association and the American Association of Equine Practitioners, both AQHA alliance partners. He advocates good working relationships between farriers, veterinarians and horse owners. To learn more about John, visit

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