Thrush is a condition affecting the frog of the foot, which can result in lameness of the affected limb.

What causes thrush?

Thrush usually develops due to poor hygiene, failure to clean out the feet regularly or if the horse is kept in damp and dirty conditions. As the hoof is continually damp and dirty it allows bacteria and fungi to invade, causing infection. The part of the hoof affected is the sulci or grooves of the frog of which there are three. One bacterium in particular, Fusobacterium necrophorum, is particularly nasty and will eat away the layers of the frog and expose the deeper more sensitive tissues. Horses with deep sulci are much more prone to developing thrush. Horses with long toes and contracted heels will tend to develop deep frog sulci.

What are the signs of Thrush?

Thrush produces a black, foul smelling, moist discharge in the affected sulcus of the frog. Affected areas will be painful when palpated with the hind feet more commonly affected. There may also be some concurrent swelling of the distal part of the affected limb.

How can thrush be prevented?

This condition is easily prevented by good hygiene – daily cleaning of the stable and regular foot care and inspection. Regular attention from a farrier ensures the development of long heels is avoided and also to keep the frog healthy.

It is also important that your horse has regular tetanus vaccinations as thrush can allow tetanus to infect your horse. Advice on vaccination can be sought form your veterinary surgeon.