By: Chelsea Farnsworth, D.V.M.
Equine pastern dermatitis (EPD) is one of the very frustrating syndromes that plagues many horses and their owners. Going by many names such as scratches, mud fever, dew poisoning, greasy heel or canker, equine pastern dermatitis often affects the back of white pasterns on hind feet, but can be found on front pasterns as well. While often called a disease, EPD is truly a syndrome with many causes, predisposing factors, and just as many treatment options.
Seen in any season and on any breed, an affected pastern can have a range of signs including redness, matted hair, thick crusts, scales, thickened skin, and discharge. Pain is variable. Mild cases are often limited to redness and some scales with little to none discharge, but severe cases can lead to lameness, swelling of the hind feet, scaring, and proliferation of granulation tissue.
Causes of EPD are varied and are often linked to environmental issues. Horses kept in wet or muddy environments, Draft horses or breeds with feathers, and horses frequently bathed are predisposed. Contact irritation, (ie. from a chemical or new bedding), a weak immune system, or infection from parasites or fungus can start the disease process. Secondary bacterial infection and environmental exposure then perpetuate the problem and makes a definite diagnosis difficult.
Diagnosis of EPD is largely based on the clinical appearance of the affected pasterns. Definitive diagnosis of the primary factor separate from the secondary causes can be difficult. Skin scrapings, which sample the top layer of skin; fungal testing, cytologies, and even a skin biopsy, may be necessary to determine the cause.
While there are many anecdotal and alternative therapies for EPD, the most important part of treating is removing the crusts and scabs. To get these off, washing with a mild soap such as Ivory may be necessary, as well as, clipping feathers or thicker hair. This step is often painful but necessary in order to get to the underlying skin.
Once the scabs are washed off, which may take several washings, various topical medications can be applied to combat the primary cause. Removing the scabs can be painful to the horse and a sweat wrap applied after application of a topical ointment may help in softening the crusts, making them easier to remove. Various antifungals, antimicrobials, and anti-inflammatories many be prescribed by your veterinarian and applied topically. Systemic medications, such as antibiotics, may be used if the EPD is severe.
Long term management relies heavily on environmental management; including: keeping the horse in a clean, dry stall during very wet weather, managing mud during the spring, and keeping feathers clipped short on draft-type breeds.
EPD, while frustrating, can be managed and working closely with your veterinarian will help in resolving this irritating syndrome.