What Thrush Actually Is

Thrush is an infection of the frog and the sulci — the deep grooves either side of the frog and the central cleft that runs down the middle of it. It is caused mainly by bacteria, most commonly Fusobacterium necrophorum, which thrive in moist, airless conditions. A hoof packed with wet mud, urine-soaked bedding or droppings is exactly the environment they need. Fungi often move in alongside, especially in long-running cases, which is why thrush can be stubborn. Left untreated, the infection can work its way into sensitive tissue and cause genuine lameness, so it is worth tackling at the first whiff.

Recognising the Signs

A little dark matter in the central sulcus is normal — most horses have some. Thrush has a very particular smell: a sickly, rotten, almost faecal odour you will notice the moment you pick out the foot. Alongside the smell, look for:

• Black, greasy or tarry discharge in the central sulcus or either side of the frog.
• A frog that feels soft, spongy or crumbly rather than firm and rubbery.
• Ragged edges or a deep, split central cleft where infection has eaten in.
• Sensitivity when you clean the sulci — some horses flinch or snatch the foot away.
• In more advanced cases, heat in the hoof, a bounding digital pulse, swelling or lameness.

If the horse is lame, or you can see a deep black tract running into the heel or sole, call your vet or farrier rather than attempting to dig it out yourself.

Why Some Horses Get Thrush and Others Don't

Thrush is not simply bad luck. Several factors tip the odds:

• Wet conditions. Standing in mud, boggy gateways or deep, soiled bedding for hours at a time.
• Hoof shape. Long toes, contracted heels and deep sulci give bacteria somewhere to hide.
• Farriery. Shoes that pack the foot with dirt, or long gaps between trims, make matters worse.
• Underlying health. Horses with Cushing's, EMS, laminitis or poor circulation are far more susceptible.
• Stable management. Deep litter beds and a horse that rarely leaves the box are a recipe for trouble.

Cleaning and Treating at Home

Most straightforward cases respond well to conscientious home care. Work through this routine daily, and be consistent — a single scrub will not fix it.

• Pick out the feet every day, twice daily if the ground is wet. Use the point of a hoof pick to clear the sulci gently, working away from your hand and never cutting into live frog tissue with a knife.
• Wash the hoof with warm water and a dilute antiseptic scrub, such as chlorhexidine or a weak iodine solution. A soft brush reaches into the grooves nicely.
• Dry thoroughly with a towel or clean cloth. Drying matters as much as cleaning; bacteria cannot thrive in a dry hoof.
• Apply a hoof treatment. Proprietary thrush preparations are widely available, and a simple dilute antiseptic dressing works well in mild cases. Follow the label and avoid caustic agents on sensitive tissue.
• Repeat daily for at least two weeks, continuing for several days after the smell and discharge have gone, until the frog is firm and dark grey again.

Do not aggressively pare the frog. It is a protective, weight-bearing structure, and over-trimming does far more harm than good. Leave any deep paring to your farrier.

When to Seek Veterinary or Farriery Advice

Home care is not always enough, and there are clear occasions when you should pick up the phone.

• The horse is lame, or the hoof is hot with a strong digital pulse.
• The infection has spread to the heel bulbs, sole or white line.
• There are deep, bleeding or pus-filled tracts you cannot clean.
• Two weeks of diligent treatment has made little difference.
• The horse has an underlying condition such as Cushing's or recurring laminitis.

A vet may need to debride the affected tissue, apply a medicated dressing and bandage, or take radiographs if infection has tracked deeper. Canker, a rarer and more serious condition with a similar smell, also needs veterinary involvement.

Preventing Thrush Before It Starts

Prevention comes down to dry feet and good routine. Pick out the feet daily, always. Provide a dry standing area — hard standing, gravel or a well-drained paddock — so horses are not permanently in mud. Use clean, dry bedding and remove wet patches rather than topping them up. Keep trimming and shoeing on schedule so the hoof stays balanced and the sulci stay shallow. Feed plenty of forage, and consider a balanced mineral supplement or biotin for hoof quality. Rotate paddocks and manage gateways, which are usually the wettest, muddiest spots on any yard.

Get into the habit of sniffing and inspecting the frog whenever you pick out the feet, and thrush will rarely get the chance to take hold.