Thrush Prevention & Treatment

By Dean Sinclair, CJF, Fe, DipWCF

With spring approaching, horse owners are eager to get back in the saddle! However, as winter transitions to spring — or during any time of year with wet and muddy conditions — hoof health can be challenged, as these environments create the ideal conditions for thrush to develop.

Thrush is an anaerobic infection (it thrives where oxygen is not present) involving the frog. It tends to proliferate in the central and collateral sulci (the grooves on either side of the frog), but can involve the whole frog as well as the area between the bulbs of the heel. The infection can lead to inflammation and low-grade lameness. The organism can also inhabit cracks and separations in the hoof wall and white line, especially if the horse is kept in a moist environment and poorly kept paddocks and box stalls.

Related: Defining a Strong Hoof: What Sets a Healthy Foot Apart?

Thrush is characterized by a foul-smelling black discharge that is related to the breakdown of the horny frog. This paste-like material is black because it is made up of dead keratin tissue. A variety of organisms can be involved with these anaerobic bacteria, with Fusobacterium necrophorum being the main culprit.

Thrush can affect all breeds and ages of horses, but draft horses are more prone to developing thrush due to the deeper clefts in their hooves, which can trap moisture and bacteria. It may also be because some owners neglect proper cleaning and regular maintenance of their draft horses’ hooves due to their size and the weight involved in lifting them.

The hind limbs of the horse are more frequently involved with thrush than the front since the organism is part of the normal fecal flora of several large animals including cattle and horses and can survive in the soil for several months. Fusobacterium necrophorum is classified as an opportunistic pathogen. This classification suggests that the environment must be right for the infection to establish itself. Most dark and poorly oxygenated environments, such as badly kept stalls and wet, muddy pastures, along with lack of regular cleaning of the horse’s feet, can lead to the development of thrush.

In advanced cases, the bacteria can invade the sensitive structures of the frog, digital cushion, and heel bulb region, leading to inflammation and lameness.

Related: Essential Hoof Care: Why Every Horse Owner Must Prioritize Daily Maintenance

Thrush is characterized by a fetid black discharge usually along the central and collateral sulci of the frog. Photo courtesy of Dean Sinclair, CJF, Fe, DipWCF

Treatment

Removal of any necrotic tissue from the frog is done by a veterinarian or qualified farrier with a hoof knife. This will ensure that the affected area is clean and exposed to whatever solution you have chosen to treat the bacteria.

There are several antifungal and antibacterial products available for the treatment of thrush. These products, along with regular cleaning of the feet with a hoof pick and wire brush (which provides oxygen to the affected area), are the best form of treatment.

Although bleach can be used to treat thrush in horses, it can damage the hoof’s protein and kill healthy tissue, so it is not recommended. Alternatives to bleach are iodine, betadine, hydrogen peroxide, or copper sulfate, which will all easily kill the thrush organism.

A product that is safe to use and can usually be found in the household kitchen is apple cider vinegar. Because of its antifungal properties, apple cider vinegar can be used quite effectively to treat thrush. A solution of one-quarter cup (60 ml) of vinegar to one gallon (3.785 l) of warm water can be used in a small bucket to soak the hoof for approximately 15 minutes.

Related: Healthy Hooves Hoof Care Guide

Due to neglect, the thrush organisms invaded the sensitive frog resulting in bleeding when cleaning the frog with a hoof pick. In this case the horse was owned by an elderly couple who were not physically able to pick up the horse’s feet to clean them out. Photo courtesy of Dean Sinclair, CJF, Fe, DipWCF

Precautions

Some remedies for thrush in horses can be dangerous to humans. These include bleach and copper sulfate. Rubber gloves along with eye-protection should be used when handling these products to protect your eyes and skin. Bleach can cause skin irritation and copper sulfate can be absorbed into the body and move throughout the bloodstream.

Related: A Farrier's Perspective - Safe Horses, Safe Spaces, and Farriers Today

Prevention

To prevent thrush following these management practices:

• Clean hooves daily.
• Keep the horse in a clean paddock or box stall.
• Provide regular farrier care. Regularly scheduled trims will keep your horse’s hooves from growing too long and trapping dirt and manure in the hoof, which can lead to the development of thrush. A healthy frog shares in the load-bearing function of the horse’s hoof and absorbs concussion each time the hoof contacts the ground. The frog also aids in traction. Regular trimming and balancing of the hoof capsule enable the triangular-shaped frog to expand and contract with each stride, pushing dirt and manure out of the grooves of the frog.

As is the case with many lameness issues, a team approach of veterinarian, farrier, and owner is crucial for success in most cases. When the horse develops thrush, the rehabilitation process will require more work from the horse owner with daily cleaning and treatment to ultimately achieve a full recovery. 

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Related: The Essential Role of Farriers in Hoof Care: Why Certification Matters

Main photo: Shutterstock/Kateryna Puchka