What is thrush?

Thrush is an unpleasant infection of the horse’s frog, which is predisposed by moist, damp, dirty ground or stable conditions.

What causes thrush? 

Thrush is an infection of the central and lateral sulcus (clefts) of the frog of the horse’s foot, most often involving bacterial and occasionally fungal infection.  One species of bacterium (Fusobacterium necrophorum) is particularly aggressive, invading and destroying the frog, sometimes exposing the deeper sensitive tissues.  Long heel conformation encourages the development of deep narrow frog sulci, which are more prone to the development of thrush, if environmental conditions are right.  If the horse has an imbalanced foot in the lateromedial (inside-outside) plane then this also predisposes the horse to thrush.

How is thrush diagnosed?

Thrush produces a foul smelling black discharge in the affected sulcus of the frog.  There is pain on applying pressure to the area.  The hind feet are more often affected than the front feet and, occasionally, infection may result in a general swelling of the distal (lower) limb.

How is thrush treated?

The horse should be moved to a dry clean environment.  The foot should be thoroughly cleaned out, removing debris from within the affected frog sulcus, and then the horn is pared out down to healthy tissue, allowing air to reach any remaining damaged tissues.  The frog and its sulcus should be scrubbed daily with dilute iodine solution or other antiseptic solutions.

Thereafter, the horse should be kept in clean, dry stable conditions and the frog should be cleaned and treated regularly until the infection is controlled and the tissues heel.

How can thrush be prevented?

Prevention is better than cure and thrush can be avoided by good stable management and regular foot care and inspection.  Stable your horse in clean dry conditions and have your horses' feet regularly trimmed and shod to avoid the development of long heel conformation and to keep the frog healthy.  Any mediolateral foot imbalance should also be addressed by the farrier.


With early treatment and good stable and environmental management, the prognosis for complete recovery for cases of thrush is good.  Treatment will usually be required for 7-14 days.  The prognosis for complete resolution is good unless the infection has been allowed to become chronic and/or there is extensive involvement of deeper  tissues. Contact the Hospital if you require assistance with a horse with thrush.


The material contained in this website is presented for information purposes only . The material is in no way intended to replace professional veterinary care or attention from a professional veterinary surgeon. 

The advice given in any of our web pages cannot be used as the basis for a diagnosis or choice of treatment.

Clyde Vet Group advises that you should always consult a veterinary surgeon about any queries with animals under your care.

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