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 of the frog of the horse’s foot, most often involving bacterial infection, 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.

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 necrotic debris from within the affected frog sulcus, and then 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.

Tetanus antitoxin must be given, if the horse is not fully vaccinated up-to-date or if vaccination status cannot be confirmed.

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.

Caution

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.

Make sure that your horses are always fully vaccinated against tetanus, an invariably fatal infection which can gain access through a damaged frog.