Thrush

What is thrush?

Thrush is a bacterial infection of the central and lateral sulcus of the frog that results in a foul smelling black exudate. It is predisposed by moist, damp, dirty ground or stable conditions, therefore is often seen in the winter months when horses are often stabled for prolonged periods of time. 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 parts of the frog and the affected tissues are soft and friable. 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, where 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 and allowed to dry thoroughly.

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 heal.

In very severe cases, surgical debridement (cleaning) and foot dressings may be required. A small number of cases can be very difficult to treat successfully, particularly if the infection is extensive.

How is thrush 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, keep the feet picked out daily and after exercise, and have them regularly trimmed and shod to avoid the development of long heel conformation and to keep the frog healthy.

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 that can gain access through a damaged frog.