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Thrush Treatment Tutorial



Thrush Medication



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Thrush is a relatively common bacterial infection that occurs within the region of the horse's frog. The infection often results in degeneration of the horn (the protective frog callous).

Thrush A

Although it was previously thought to be a fungal disease, we now know that thrush is of bacterial origin. Fusobacterium necrophorum, an anaerobic microbe (most suited to living in an environment lacking oxygen), is the most common infectious agent associated with thrush in horses. This organism is a normal resident of soil and animal feces, and can be keratolytic in nature (eroding underlying corium and horn).

When it sets up residence in the horse's hoof, F. necrophorum generally localizes near the frog and is usually most prevalent in the collateral sulci (the grooves adjacent to and in the middle of the triangle-shaped frog) and/or in the central sulcus (the cleft between the heels). Because this microbe is anaerobic, it thrives in a moist, dark, poorly oxygenated environment.

Thrush B


The establishment of this bacteria manifests in several ways:

  • Repulsive odor

  • Watery or oily discharge (often black in color)

  • Tenderness in the frog region

  • Fissures or deep pockets extending to the heel bulbs

  • Loss of frog shape and integrity

Standard texts on equine health often suggest that horses develop thrush as a result of sub-standard living conditions. Although there's little doubt that compromised surroundings (particularly wet conditions) will promote thrush, most farriers agree that this issue is a more complicated and can't be explained away by pointing at dirty stalls and mud puddles.



We have identified a few common causes of thrush within our practice:

  • CHRONIC HEEL PAIN. As you might expect, horses with pain along the palmar aspect (back) of the foot tend to underload this area. The heels, like all other aspects of the foot, are dynamic in nature and respond to applied forces. This is why chronic underloading of the heels results in their contraction. Contracted and/ or high heels produce deep frog sulci, which provide an exceptional environment within which anaerobic bacteria can proliferate. At The ATLANTA Equine Clinic, our first objective when treating a horse with thrush is to resolve any issue(s) that might predispose the horse to chronic underloading (and contraction) of the heels. In our experience, successful management of these issues (the most common of which is thoracic navicular inflammation) eradicates the thrush (which would be considered secondary to the contracted heels) in more than half of the cases.

  • LACK OF EXERCISE. In our experience, one of the more important factors in avoiding and/or eliminating thrush is exercise. For example, horses living in manure and mud might be working hard each day, getting a lot of activity and moving in a natural manner that promotes good vascularity (blood supply) in the foot, which is key to keeping the hoof healthy. Whereas horses standing in clean/ dry stalls are simply standing, and are not promoting the same kind of vascularity necessary to generate a healthy foot.

  • REGULAR FARRIERY. The horse that is receiving regular maintenance from a farrier will maintain a more balanced and supportive hoof. Such balance lends itself to even loading, compression, and concussion, all of which promote good vascularity and overall foot health. Impaired blood circulation ranks high on the list of causes of thrush. On average, the circulation in a shod or peripherally loaded hoof is approximately 20% of what it is in a healthy barefoot hoof. Moreover, most shod horses land toe-first or flat. The primary problem in these feet isn't thrush, its impaired circulation and incorrect use of the foot.

  • FROG CONFORMATION. Open and calloused, atrophied or over trimmed frogs may be susceptible to development of thrush. Frogs with deep cracks, crevices and flaps are also prone, as they are robbed of their protective horn.

  • DIET HIGH IN CARBOHYDRATES. There may be a dietary component as well, as horses on high carbohydrate diets seem more likely to be affected with thrush.

  • HOOF CONFORMATION. Horses may walk on the sides of their feet or favor their toes when they have thrush to avoid "hoof mechanism", the flexion in the hoof that enables shock absorption. Good blood circulation is necessary for a healthy frog, so good heel-first movement is a priority.

  • PREVIOUS INJURY. Horses sustaining an injury that results in favoring of one limb over another often end up with a contracted heel on the foot of the affected limb. Contraction can result in the development of crevices that welcome proliferation of anaerobic bacteria.

  • ENVIRONMENTAL DEFICIENCIES. Of course wet footing is the primary concern, as it creates and environment amenable to bacterial growth and proliferation.

  • POOR HYGIENE. Chronic exposure to urine, which contains ammonia, can dissolve the proteins that comprise the frog's horn.


Thrush C

Thrush becomes a problem when blood supply, movement, hygiene, environment, diet or hoof care aren't what the horse requires, and the resulting bacterial imbalance creates an opportunity for thrush to take root.



A good thrush prevention plan includes trimming or shoeing horses properly, exercising animals regularly, and keeping a good horse maintenance plan that includes regular hoof care and a clean living environment.

Once all other factors have been successfully addressed, we generally recommend daily application of topical medication to "dry out" affected tissue and resolve any residual infection, which we consider to be a secondary component of thrush.


Thrush Medication

Click HERE to learn about effective topical therapy for THRUSH.





If you have any questions regarding Prolotherapy for your horse please call our office at (678) 867-2577. We look forward to serving you!
THE ATLANTA EQUINE CLINIC: 1665 Ward Road, Hoschton, Georgia 30548 - ph. 678-867-2577

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