F E A T U R E
Hoof Abscesses Horse Care by HEATHER SMITH THOMAS Your horse is suddenly lame, with heat and swelling above the hoof. One possible cause is an abscess. Scott Morrison, DVM, Rood and Riddle Equine Hospital, says most hoof abscesses start as either an ascending infection that’s worked its way up from the white line or bars or from a direct puncture wound. Causes Bacteria may gain access to the foot via many routes. The white line between sole and hoof wall, or the junction between bar and sole may be compromised, especially in wet weather, enabling bacteria to enter. “This is one of the most common causes of an ascending infection, up through the white line. This is what horsemen often call gravel (an infection that probably starts at the white line and travels upward, breaking out at the coronary band or at the heel). Another common cause is puncture wounds. These can be anywhere in the foot,” he says. “Weak feet with flares or dishes are more likely to develop abscesses because the tissues are stretched in those areas.” There’s less structural integrity to the white line. Openings at the ground surface invite bacteria. Thin, weak soles that are easily bruised may also lead to abscesses. “The sole is soft and spongy. A bruise may readily become an abscess if there’s a serum pocket. This creates a perfect environment for bacteria to flourish,” says Morrison. Cracks in the hoof wall may lead to an abscess, if they go clear through the wall. “Any time the hoof barrier is breached by any kind of crack, flare, dish, or defects in the white line, bacteria can enter,” he explains. “One thing that’s risky is trying to fix toe cracks by filling them with glue. This is really dangerous because you never get the crack perfectly clean and may seal in bacteria.
An overnight soaking boot made by using an IV bag to contain the soaking fluid and protected by duct tape around the bottom of it.
58 CALIFORNIA THOROUGHBRED • DECEMBER 2012
It’s a perfect environment for them to multiply. Any time we do a hoof wall repair or crack repair, it’s very important to pack off the bed of the crack with cotton and antiseptic, so we don’t have to glue directly onto the bed of the crack. Those will almost always abscess if you don’t create a barrier between the glue and the crack.” Horses with laminitis are prone to abscesses because their white line is more stretched than normal. “It’s not a nice, tight junction between sole and wall. It’s pulled apart and has little spaces where bacteria can enter and work their way up. Seedy toe or separations at the ground surface of the hoof wall can often lead to infection, as well.” In Kentucky, one problem he sees a lot in winter when ground is frozen is cracked soles and bars. “The foot is generally fairly soft because the ground may be wet with mud or snow. The soft foot may hit some uneven frozen mud or ice—and crack the sole or bar. Subsolar infections may develop, secondary to the crack in the bar or sole. These infections generally respond well to protecting the sole. We usually just shoe with a treatment plate (to give access to the bottom of the foot for medication) to protect the foot, and the horse generally goes sound fairly quickly,” says Morrison. Getting the sole up off the ground and protecting it, after initial poultice treatment, will help it heal. “Wet weather is one of the most common predisposing factors. The foot acts like a sponge and gets soft, and the white line is stretched—making it easy for bacteria to work their way up it.” Thrush can also lead to an abscess if neglected. “Bad cases of thrush may get deep—into the digital cushion or close to the deep digital flexor tendon sheath. I’ve seen some horses slough off the entire frog after a bad case of thrush,” says Morrison. Clinical Signs “The most obvious sign of an abscess is severe lameness in one foot. It may come on slowly or suddenly. It probably depends on the number of bacteria that gained entry. If it was a fairly number that multiplies rapidly, this may create a lot of inflammation and pressure, much faster than if it were just a few bacteria that take more time to multiply to that level,” says Morrison. “There is heat and swelling, and when you examine the foot there’s usually a sharp response to a hoof tester when that area is pressed. If the abscess is not opened up to drain, a few days later the infection may migrate to the heel bulb or coronary band—and then you’ll see a pain response at the hair line or heel bulb when pressed,” he says. Once the infection erupts out through that soft tissue the pain level decreases.
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