Abscesses occur when bacteria get trapped inside the hoof (see photo). Trauma to the hoof sole from sharp objects such as nails, screws, and glass may carry bacteria and debris into the hoof from the outside environment. A horseshoe nail that is inside the white line (the junction of the hoof wall and sole), may also provide a route for bacteria to enter. Bacteria can also enter the deeper structures of the hoof when the hoof quality is poor and unable to protect the tissues properly. Poor hoof quality may be genetic or environmental. With wet winter and spring weather and in wet dirty stalls, the hoof wall can soften, permitting bacteria to migrate through the gaps in the white line. Very dry conditions, or alternating wet/dry weather, leads to brittle feet that are more likely to develop hoof cracks. Finally, poor hoof care resulting in long flared toes or crushed heels weakens the integrity of the white line and increases the risk of hoof abscesses.
Most often with hoof abscesses, the horse becomes severely lame overnight. The hoof is like a fingernail in that there isn't much room for swelling; when pressure builds up it causes an extreme amount of pain and results in severe lameness. It is not uncommon for the owner to be worried about a fracture due to the degree of pain/lameness.
Owners will likely not find any external wounds or swelling. If a nail or other object is seen in the hoof, resist the temptation to remove it and call your veterinarian immediately. The site and angle the object enters the foot will be important information for a veterinarian. Severe abscesses can lead to swelling and infection that extends up the leg. Owners may notice swelling and inflammation of the pastern (cellulitis), or swollen heel bulbs and coronary band. Often the hoof wall is warmer than usual and the pulses in the pastern region are more readily felt.
A veterinarian will take a thorough history, and perform a lameness exam to ensure there are no fractures or other injuries. Hoof testers are used pinch parts of the foot, trying to elicit a localizing pain response. Sometimes, a crack or track can be identified after the hoof is cleaned and the old sole is scraped away. If a suspect area is found, a paring knife can be used to encourage the infection to drain. Some horses will need analgesics or local nerve blocks for this procedure. If no draining tract can be found, radiographs may be performed to look for gas (produced by the bacteria) within the hoof, as well as ruling out other potential causes for lameness.
Horses with a mild infection can return to work in less than a week. Deep infections can take several weeks to heal and can lead to laminitis if not well-controlled. Call a veterinarian if:
- The drainage continues after 48 hours or increases after that time
- The horse remains painful or needs analgesics for more than 1-2 days
- The horse loses its appetite
- The horse shifts his weight frequently, rests his good leg or lies down more than usual
- Tissue (proud flesh) grows out of the drainage hole
The goal of treatment is to drain the abscess and prevent further contamination. Due to the level of pain, it isn't humane to wait for the abscess to rupture on its own. A veterinarian will try to pare away a hole, just large enough to allow drainage of the pus pocket. The pain relief is usually immediate.
After the abscess is opened, an antiseptic dressing, such as providone-iodine or a medicated poultice pad (i.e. Animalintex Poultice Pad) is applied to keep the abscess draining for the next 48 hours. A waterproof bandage such as a diaper applied with duct tape, or a hoof boot, is used to cover the poultice and hoof. It is imperative that the protective bandaging/boot stays clean to prevent prolonged infection and contamination of the draining hole. The horse should remain in a dry area, such as a clean, well-bedded stall, or small dry paddock with the bandage removed and changed daily. After the first 48 hours, antiseptic compounds and clean bandaging will generally suffice until the drainage stops and the wound is dry, however, the horse should remain in a clean, dry area.
Multiple, daily warm water and Epsom salt soaks were previously considered an important part of therapy; however, it has been found that excessive soaking only further weakens the hoof and may have negative effects. Tap water soaks do help moisturize the sole, however, a veterinarian may recommend occasional foot soaks to encourage drainage. Phenylbutazone, firocoxib (Equioxx), or banamine may be prescribed if needed for pain relief or swelling control. The hoof bandage should remain in place until the drainage stops, the hole is dry, and the lameness is gone.
To prevent future hoof abscesses:
- Maintain a clean, dry environment with routine stall cleaning and manure removal from paddocks.
- If extreme changes in weather conditions are expected, hoof hardeners can be applied to protect the hoof wall from too much moisture, and dressings such as pine tar can be used to hold in moisture during drought.
- Routine farrier care is important to maintain good hoof quality and strength.
- Remove any nails, farm implements, metal pieces, and glass from the environment to minimize the risk of trauma.