A hoof abscess is a collection of dead material located within the white line or under the sole. Abscesses may be sterile (dead tissue only) or infected with bacteria. They occur in the tissue at the junction of the sensitive (live) and insensitive (dead, hoof wall or sole) laminae.
Unless there has been a puncture wound, sole abscesses are almost exclusively caused by tissue damage. Over thinning the sole by the farrier or a stone bruise could result in an abscess. Abscesses in the hoof capsule can have many causes. Driving a horseshoe nail too close to, or into live tissue, is another common cause.
Sterile abscesses, which are abscesses without a bacterial infection, are common following laminitis and will often surface after the horse has been taken off anti-inflammatory drugs, like phenylbutazone or Banamine.
Prolonged periods of wet weather can also contribute to hoof infections, especially in horses that don’t have healthy, tight white lines. Going too long between trims increases the risk of abscesses because the white line becomes stretched and can develop gaps, and even microscopic gaps are an avenue for bacteria. Nail holes in horses that are shod widen over time and bacteria can enter there (some farriers seal nail holes, which may help).
The body’s reaction to a pocket of dead tissue or infection is inflammatory. The tissue swells and white cells enter from the blood. A layer of dense connective tissue will form around the area to seal it off from the rest of the body. The pain from an abscess is typically even worse than from laminitis. The horse may completely refuse to put weight on the hoof.
Diagnosis. Diagnosing abscesses can be challenging. The rapid onset of severe pain and the severity of the pain itself always suggest abscess, but your veterinarian may want to do X-rays to make sure it is not laminitis or a fracture.
The horse’s reaction to hoof testers will vary, so it’s not foolproof. Thermography, a technique that detects heat, can be helpful, but you may be able to detect an area of warmth with your hand.
In a subsolar abscess, an area of softening may develop. With hoof-wall abscesses, the coronary band will begin to swell in the area where the abscess is going to exit. Although the pain of an abscess is severe, the relief the horse gets when it begins to drain is equally dramatic.
Treatment. To speed things along, soak the hoof as often as possible in hot water with Epsom salts added. If you can’t soak, pack a warmed poultice into the sole and around the coronary band/heel bulbs. Numotizine (www.numotizine.com, 218-751-9505) works particularly well for this and it will turn color from its pinkish gray to black over any areas that are draining or oozing. We’ve also found that Epsom salt poultices, which cost about 50?? an ounce, work well on abscesses (www.kaeco.com, 800-228-1211; www.gpdirect.com, 888-472-2825; www.durvet.com, 800-821-5570).
Subsolar abscesses may exit through the sole, but it is more common for them to drain around the tip of the frog (where sole is thin) or where the bar and hoof wall meet.
Paring the sole over subsolar abscesses is somewhat controversial because it exposes live, sensitive tissue and the areas are difficult to keep clean. Some veterinarians prefer to make a small opening in the hoof wall above the the level of the sole to allow the collections to drain that way.
Aftercare of abscesses that have ruptured isn’t complicated. Solar openings should be kept in a hoof pack or booted until the layer of sole has reformed. Use ichthammol, an inexpensive black drawing salve, on the area to encourage more drainage.
For exit spots on the coronary band or heel bulbs, keep the area cleaned of discharge because this is irritating to normal tissues. The cavity itself needs no special care because it’s walled off from the live tissues. In the rare instances where tissue seems to prolapsing/popping out of the exit site, call your veterinarian. As the hoof grows, the hole will grow down as a visible slit.
Although abscesses are painful, anti-inflammatory drugs should be limited to horses that aren’t eating and drinking well because their use may slow the process of the abscess maturing. Soaks help ease the pain.
Antibiotics can also slow the process in infected abscesses, without reaching good-enough concentrations to actually kill the organisms. Your veterinarian will usually recommend these if infection is climbing into the tissues of the pastern and lower leg (cellulitis).
Bottom Line. If you don’t have a nearby tack store where you can quickly pick up the supplies, you’ll want to have an abscess kit on hand. The quicker you get the treatment started, the better.
Both kits in our trial surpassed the homemade method in terms of both cost and simplicity. We found that the difference is actually in the boots, which put the Kaeco kit on top for us.
Article by Eleanor Kellon, VMD, Veterinary Editor.