Thrush in horses is a foul smelling bacterial infection affecting the feet. It should not be confused with canker, which is an altogether more serious infection. Fortunately, canker is rare as it is a difficult condition to cure, whereas thrush usually resolves with correct management.
Careful stable and hoof management is essential if thrush is to be prevented. As the bacteria are killed by oxygen, regular use of the hoof pick will allow air to the foot and reduce the ability of the bacteria to take hold.
Keep stables clean with plenty of good-quality, dry bedding. If horses are in for long periods, bank the beds during the day to allow them to stand on an area of clean, dry concrete.
Some horses are more susceptible to this condition than others, and foot conformation can lead to a predisposition to thrush. For example, a deep cleft in the frog may become packed with sand after working in an arena. If not carefully cleaned, this could lead to irritation and allow bacteria to enter.
The prime cause, however, is one of hygiene — standing in droppings and urine. The damp conditions of a dirty stable provide the perfect environment for the anaerobic bacteria, (those needing a low-oxygen environment) which cause thrush to flourish.
Diagnosis and treatment
The most obvious sign of thrush is a foul-smelling, black discharge from the frog, which itself may have softer spots and appear irregular in shape. The horse is unlikely to be lame unless the decay has invaded the sensitive inner tissues.
If a horse has thrush the underlying cause needs to be identified and removed. The horse should be moved to a clean, dry environment and the feet cleaned daily.
The farrier or vet will need to remove the decayed tissue, and depending on the severity of the condition, this may need to be done over more than one visit. The feet may need to be bandaged or dressed with topical medication. Every vet and farrier has their favourite remedy, most of which aim to dry out the feet.
Thrush will never resolve unless the hoof hygiene is good — it is the equine equivalent of athlete’s foot. A damaged frog is the perfect entry point for the bacteria that cause tetanus, so ensure that the horse has adequate protection against this.
Vet Karen Coumbe says: “Thrush should be relatively easy to sort out. If it lingers, review your management or consider whether it could be the more serious condition of canker. Draught horses are more high-risk canker candidates.”