Thrush in horses is a degenerative infection of the central and collateral grooves of the frog. In classic cases it results from the softening and damage to these soft tissue structures of the horse’s foot through standing on wet, dirty bedding. Keratonolytic (keratin-loving) bacteria, including the sheep foot rot organism fusobacterium necrophorum, attack the softened tissues of the frog, causing it to rot away. 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. Despite the grisly smell and discharge, the horse often appears completely unperturbed by its unsociable affliction, with no apparent discomfort or lameness evident. If the infection is severe it can underrun the adjacent sole and spread to involve the deeper structures, such as the digital cushion, hoof wall and heel bulb. Then there may be some pain on palpation around the frog and bulbs of the heel, together with filling of the limbs and a varying degree of unsoundness.
What causes thrush in horses?
- Unhygienic environmental conditions: Stabling for prolonged periods on soiled, sodden bedding; turnout on constantly damp, swampy or marshy pasture. 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.
- Poor foot conformation (especially of the frog): Long narrow feet, prone to contracted heels, with associated small, narrow frog and compressed involuted central groove; sheared heels, where a gap develops between the bulbs of the heels due to a chronic foot imbalance; an acquired frog deformity, perhaps as the result of an injury. 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.
- Poor or incorrect foot trimming/shoeing: A badly fitting frog plate of a heart-bar shoe can damage the frog, leading to a secondary infection; a badly shaped shoe, nailed too far back, can prevent expansion and contraction of the heels, leading to shrinkage and possible “rotting away” of the frog; shoeing with full pads, allowing dirt and moisture to collect and fester.
- Poor foot care: Not regularly picking out and cleaning the feetTraditionally, thrush has suffered bad press and is commonly considered a product of bad stable management. This is definitely not always the case. Some horses kept in foul underfoot conditions are unaffected, while others in perfect accommodation are. The individual susceptibility of the horse seems to be a major factor.
The best way to cure thrush and prevent it from recurring is to solve your horse’s original hoof-capsule abnormality. Your farrier will need to trim his hooves in a way that puts the frog and heels of the hoof capsule back on the same plane. Depending on your horse’s conformation and trimming history, this may just be a matter of rasping down his heels. Once the frog is level with the rest of the foot again, its restored function will promote new, healthy growth.
Initially, your farrier will also treat the thrush much like a dirty wound, trimming away the loose, diseased frog tissue and possibly applying dilute bleach. You can follow this up with applications of a mild astringent, such as Betadine®, or another anti-thrush product. (Note: Never use an iodine solution stronger than 2 percent as this is extremely caustic.) I prefer to switch anti-thrush solutions daily for a week. Severe cases will improve faster if you switch from straw bedding, which holds more moisture against the horse’s hooves, to shavings or sawdust. All of these treatments are secondary, though, and will only be effective if the hoof is also trimmed appropriately. Once the frog is back on the same plane with the rest of the hoof, it will become healthy and should heal quickly.
ThrushBuster (Second Favorite)
Apple Cider Vinegar and Copper Sulfate ( My favorite)