Here’s how one veterinarian treated a particularly challenging case of this common skin condition

When Sarah Pell, DVM, of Genessee Valley Equine Clinic (GVEC), in Scottsville, New York, visited a regular patient in the height of mud season, she wasn’t surprised to find the 18-year-old Quarter Horse gelding had pastern dermatitis, also known as scratches, mud fever, dew poisoning, or greasy heel. The skin condition, which commonly appears on the heel bulb, pasterns, and around the fetlocks, is triggered by wet conditions, including mud, standing water, and damp bedding. Bacteria and fungi living in these conditions find their way into even the smallest cracks in the skin, creating an infection.

“Mud season,” which used to be confined to fall and spring in New York state, now often extends into January and February. Like most horses the practice sees, the gelding was on turnout during the day and brought into his regularly cleaned stall overnight for the winter months.

In consistently moist conditions and/or stalls that are not cleaned enough, it’s not uncommon to see horses with scratches, says Pell. There are many over-the-counter topical protocols that owners typically try prior to calling Pell and her colleagues at GVEC out for evaluation.

“We have conversations (with horse owners) about scratches mostly during annual wellness visits unless the scratches have become severe or cause secondary problems like infection, swelling, or lameness,” she says.

That was the case for this Quarter Horse. During his annual physical exam, his owner mentioned that the horse had developed scabby crusts on the pasterns of both hind legs.

“The crusts were moderate and did not appear to be super painful,” says Pell. “In severe cases, we have to sedate the horse to work on the lesions because the leg is so painful to the touch. When I see a case of scratches like this, one of the first steps is to clip away the hair surrounding the affected area.”

While scratches can appear in any horse, they are more common in breeds with heavy feathering. The excess hair traps moisture close to the skin, creating the prime conditions for pastern dermatitis to develop. Clipping the hair around the pastern and fetlock allows moisture to wick away from the skin and gives it a chance to dry out.

After clipping the hair, Pell instructed the owner to shampoo both hind legs daily for one week using Betadine scrub (dilute) or Selsun Blue medicated shampoo. For best results she advises letting the shampoo sit for 10 minutes on the affected area before rinsing. After seven days she told the client to continue the washing protocol two to three times a week for several weeks. She instructs owners to avoid picking at or pulling off the scabs despite how tempting it may be.

After cleaning the affected area and letting it dry thoroughly, she recommends applying Desitin, the cream used to prevent and treat diaper rash in babies, to create a barrier against moisture. Typically, after following this course of treatment, the condition should show signs of improvement within a month.

“It takes some time for skin conditions in all species of animals to clear up,” she says. “But call your veterinarian sooner if you notice the scabs spreading or the limb is swollen or painful.”

A Lingering Case of Scratches

Unfortunately, despite this horse owner’s efforts, the gelding’s condition worsened. His leg became painful to the touch and the lesions began draining. At this point Pell prescribed an oral antibiotic.

“At our clinic we make a topical ointment with a steroid that acts as a barrier, provides pain relief, and reduces inflammation,” she says. “There isn’t a universal topical out there for scratches (because) it’s very horse dependent.”

Pell also advised keeping the gelding in a stall for a minimum of seven days while continuing to do the shampooing protocol. Luckily, this was feasible, and he tolerated being stalled.

“Some people aren’t set up for stalling a horse, or the horse can’t tolerate it,” says Pell. “But in persistent cases, keeping horses out of the mud is ideal.” If a facility has an indoor arena, the horse can be turned out in that dry environment to alleviate some boredom.

A Long Road

Despite the horse owner diligently treating the scratches, they still persisted six months later. Since this gelding was older, she tested him for PPID (formerly known as equine Cushing’s Disease) to rule out systemic factors that could delay healing. The results were negative, so Pell’s next step was to remove some of the crust and submit it for a tissue culture to determine if a different antibiotic was necessary.

“There is no great way to treat scratches,” she says. “Even when treated very diligently, it may take several months to resolve fully.”

Fortunately for this particular horse, the scratches responded well to a different antibiotic. However, in rare cases pastern dermatitis can be so severe that it might even cause lameness or secondary cellulitis, says Pell. Cellulitis is an infection in the subcutaneous skin layer that often presents with clinical signs such as severe lameness and heat, swelling, and pain on palpation of the limb.

“A majority of these horses may have a fever as well,” she says. “If you notice any of these signs, call you veterinarian as the horse should be seen.”

When treating cellulitis it is important to reduce inflammation and control the infection, she adds. Your veterinarian might also treat your horse with a non-steroidal anti-inflammatory drug (NSAID) such as phenylbutazone (Bute) or flunixin meglumine (Banamine), and an antibiotic. Hydrotherapy is important in these cases to reduce the swelling, as well as hand-walking once the horse becomes more comfortable on the affected limb.

The Long-Term Prognosis

While pastern dermatitis can be inherently frustrating for horse owners, veterinarians say the long-term prognosis is typically favorable, and the horse usually can continue his lifestyle.

“Managing mud season is always difficult,” Pell says. “I always recommend getting the mud off the legs if a horse is on turnout, especially if they are coming in wet or muddy. Hose off the legs and towel dry, especially if the horse is more prone (to developing scratches), and apply a barrier like Desitin.”

Prevention might not be 100% possible, and scratches often occurs seasonally; however, Pell notes that checking your horse’s legs frequently and taking action early can help shorten the duration. “Look at your horse’s legs daily if you can,” Pell says. “If you notice something developing, even if it’s mild, keep a close eye on it and start getting those legs dry and clean. Give your horse time out of a wet environment for his leg to dry out. Don’t wait until it’s more of a problem because it’s much easier to resolve scratches in its early stages.”