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Key takeaways

Thrush is a common bacterial infection of horse hoof tissue caused by Fusobacterium necrophorum.

  • Symptoms of thrush include a foul odor, watery or oily black discharge surrounding the frog, tenderness in the frog region, and loss of frog shape and integrity
  • Diagnosis is usually straightforward due to the obvious clinical signs of thrush
  • Treatment of thrush typically requires daily hoof picking, cleaning, and application of medicated thrush products
  • In more severe cases, a veterinarian may prescribe systemic antibiotics
  • When diagnosed and treated early, uncomplicated cases of thrush are expected to resolve fully
  • More severe cases of thrush can result in permanent lameness
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A closer look: Hoof Thrush in Horses

Symptoms of thrush can vary depending on the severity of the infection. Mild cases of thrush do not cause lameness, but in more severe cases the infection can invade the sensitive layers of the foot, the white line, and sole. Left untreated, these infections can potentially result in permanent lameness.

When diagnosed and treated early, uncomplicated cases of thrush should resolve fully. More complicated cases of thrush where the infection has invaded the deeper tissues of the foot can take longer to resolve. These cases require veterinary attention and may result in permanent lameness.

Risk factors

Thrush is common and can occur in any horse, regardless of the cleanliness of their living conditions.

Risk factors for thrush include:

  • Poor foot conformation
  • Inactivity
  • Moist conditions
  • Poor diet
  • Poor hoof growth
  • Insufficient or lack of trimming/shoeing
  • Chronic lameness

Horses with deep sulci surrounding the frog that have narrow or contracted heels appear to be at increased risk for thrush. Reduced exercise disrupts the horse's natural hoof-cleaning mechanism, allowing for accumulation of material inside the hoof that provides a suitable environment for bacterial growth.

The prognosis for thrush is usually favorable with appropriate treatment and early diagnosis. Recurrent or severe, damaging infections are likely to occur if the source is not identified and treated.

Possible causes

Thrush is caused by Fusobacterium necrophorum bacteria that proliferate in the hoof tissue, causing an infection.

Main symptoms

Symptoms of thrush include

  • Repulsive odor
  • Watery or oily discharge (often black in color)
  • Tenderness in the frog region
  • Fissures or deep pockets extending to the heel bulbs
  • Loss of frog shape and integrity

Testing and diagnosis

A veterinarian typically diagnoses thrush based on clinical signs such as repulsive odor, black debris/discharge, and frog loss. Tissue culture to identify the disease-causing microorganism is available to confirm diagnosis, but usually is not necessary or performed.

Steps to Recovery

Treatment of thrush involves:

  • Trimming away dead or infected tissue
  • Daily hoof picking, cleaning, and medicating the affected foot

Medicated thrush products are commercially available and usually require daily use for horses with active thrush infections. Consultation with a veterinarian is recommended, as some products cause chemical burns if applied incorrectly. After handling thrush treatment products, wash hands thoroughly.

For horses that appear not to be responding to treatment, or in more severe cases, a veterinarian may prescribe systemic antibiotics. Depending on the damage to the hoof and heel, corrective trimming and shoeing may be warranted.


Thrush prevention involves regular turnout in clean, dry environments and routine exercise to promote natural hoof cleaning. Hoof inspection, picking, and cleaning are also important in the prevention of thrush. Regular hoof maintenance by a farrier ensures a more balanced, supportive hoof.

Long-term management strategies include:

  • Increasing exercise or activity
  • Evaluation of the horse’s overall health
  • Changes in trimming or shoeing
  • Changing turnout to a dry, clean environment

Is Hoof Thrush in Horses common?

Thrush is common in horses.

Typical Treatment

Typical treatment of thrush involves:

  • Trimming away dead or infected tissue
  • Identifying and correcting the underlying cause(s) of the infection
  • Daily hoof picking, cleaning, and medicating the affected foot
  • Stimulating the frog through regular exercise


James K. Belknap , DVM, PhD, DACVS - Writing for Merck Veterinary Manual
Stacey Oke, DVM, MSc - Writing for The Horse
Danvers Child, CJF - Writing for The Horse
Raul Bras, DVM, CJF - Writing for The Horse
Marcia King - Writing for The Horse
Nancy S. Loving, DVM - Writing for The Horse
EDITORS OF PRACTICAL HORSEMAN - Writing for Practical Horseman

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