Painful hoof abscesses in horses develop when bacterial and fungal organisms enter the hoof structure through a wound or opening and cause infection in the inner tissues.

The invading microorganisms and the ensuing immune response generate purulent exudate (pus) which causes pressure inside the hoof. This leads to pain, structural damage and lameness.

To prevent potentially permanent damage and suffering, hoof abscesses should be treated promptly.

Clinical examination including a lameness evaluation, the use of hoof testers, and radiographic imaging can aid in the diagnosis of the condition.

Abscesses are treated by promoting drainage of the exudate within the hoof and clearing the infection from it. Supporting hoof growth and a strong hoof structure is critical to regaining comfort and mobility.

What is a Hoof Abscess?

A common cause of sudden lameness, hoof abscess refers to an accumulation of discharging liquid (pus) that is produced by infected tissue within the foot of the horse.

Equine hoof abscesses develop beneath the sole of the hoof and behind the hoof wall. [1][2]

Hoof abscesses can develop if microorganisms gain entrance through the hoof capsule (the epidermal layer) into the inner tissues of the hoof (the dermal layers).

Once inside the hoof, these microorganisms become trapped between the sensitive laminae (the tissue layer that bonds the hoof capsule to the coffin bone) and the hoof wall or sole and propagate. [3]

Bacterial Infection

The microorganisms involved with hoof abscesses promote the accumulation of exudate (pus) behind the hoof wall or sole and cause an increase in pressure in the hoof capsule. The increased pressure causes the horse immense pain. [4]

Bacterial entry into the hoof capsule is made possible through a crack or break in the tissues of the hoof. Infectious organisms may penetrate the hoof in the following ways: [1]

  1. A defect or separation in the wall of the hoof
  2. A crack in the junction between the wall and the sole of the hoof
  3. A puncture wound on the solar surface of the hoof in the sole or frog

Hoof abscesses are very painful for affected horses and severe lameness can result very quickly.

If left untreated, abscesses can spread throughout the tissues within the hoof and compromise the podotrochlear (navicular) apparatus if there was a puncture in that region, potentially resulting in permanent damage to the hoof and its internal structures. [5]

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Causes of a Hoof Abscess

Microorganisms must gain entrance into the hoof capsule to initiate the development of an abscess. The most common ways microorganisms can enter the hoof capsule including the following: [4]

  • Foreign objects such as nails, screws and glass can penetrate the hoof
  • Horseshoe nails placed inside in the area where the hoof wall meets the sole (in the white line)
  • Poor hoof quality due to genetic or environmental factors may compromise the integrity of the hoof
  • Wet conditions caused by rainy weather or dirty stalls can cause the hoof to soften and become vulnerable to bacteria entering
  • Brittle hooves caused by fluctuating moisture levels in the environment can promote cracked hooves
  • Improper hoof management that causes flares or crushed heels can weaken the hoof structure and cause fissures
  • Nutritional deficiencies, including in methionine, biotin, zinc, copper and essential fatty acids can compromise the integrity of the hoof wall and white line, lowering the ability to resist infection

All horses can be affected by hoof abscesses. Hoof abscesses are most likely to occur during the wettest seasons of the year including the spring and winter, although they can occur at any time.

How a Hoof Abscess Develops

An abscess forms after foreign material has entered the hoof through an open fissure and subsequently migrated deeper into the structure to form a tract inside of it.

The pressure exerted on the hoof due to the weight of the horse promotes the migration of the microorganisms into the innermost dermal tissues.

The immune system initiates an inflammatory response inside the dermal tissues of the hoof capsule in response to foreign debris in this area. [1] As the invading microorganisms propagate in the tissue, inflammatory cells infiltrate the affected area.

The release of enzymes from the inflammatory cells and microorganisms promotes the death of cells in the tissues (necrosis) and the development of a grey/black colored exudate. [1]

The accumulation of exudate and the presence of inflammation in the tissue elicits a painful response in the horse because the hoof is unable to accommodate swelling.

A hoof abscess forms as the body responds to the infection in the affected tissues by sealing off the area with a thin layer of fibrous tissue. [1]

Clinical Signs of a Hoof Absces