Maybe it’s called scratches because even a minor scrape in the skin of the pastern can start this annoying and hard to treat problem. In some parts of the country it is called grease heel, and in others, mud fever. Both of those names are descriptive. The official name is pastern dermatitis. It is usually seen on the hind legs of horses with thick leg hair and most often in wet weather. The moisture trapped by the hair is the perfect breeding ground for a mixed bag of bacteria and fungi. With even the smallest break in the skin, microbes enter and the problem begins. Abscesses erupt at the back of the pasterns and ooze serum. Serum is sticky, and dry it hardens like glue, adhering tightly to skin and hair. If you aren’t familiar with what this looks like, Google “scratches horses” and check out the photos.
I never write articles about subjects that I don’t have plenty of personal experience with. It would be fine with me if I never saw another case of scratches, but I can tell you that I will, for sure, before the month is out. I always check the books and do on line searches before writing to see if there is something beyond my experience that I have been missing. My research on the subject of scratches subject tells me that not much has changed over the past 50 years. It has always been a problem, and will continue to be.
The condition is more common in horses with that magnificent long hair that extends from just below the hocks and knees all the way to and covering a bit of the foot. Any veterinarian will tell you that white legs are especially susceptible. So those long white “feathers” make horses of the Clydesdale breed ideal candidates for the problem. Get any two owners of Clydes together, and eventually the talk will turn to how they are dealing with scratches.
Cleaning the area is hard to do and painful for the horse. Just clipping the hair to get down to the skin becomes a real challenge. Even when you declare victory, it often reoccurs. Horses that get scratches are apt to be repeaters, so daily inspection of legs by owner or trainer is important. There is some thought that horses with weak immune systems are more likely to get the problem. Medications that stimulate the immune system are sometimes used with the idea of speeding up the healing process.
My own experience with the problem has taught me a couple of things I’d like to pass on. First, if there are multiple draining abscesses and your horse resists your trying to pick or scrub them off, let ichthammol do the work. This is an old time ointment that is available at any horse supply. Use a tongue depressor and smear it onto the leg as thick as you would chocolate frosting on a cake. Over the ichthammol use sheet cottons or a quilt, secure with a leg wrap, and keep the leg done up for two to three days. If the scabs don’t come off easily after that, repeat. This ointment does an outstanding job of loosening the caked on skin eruptions and in soothing the irritated skin. When it’s time to remove the wraps, scrape off any excess ichthammol and wash the leg gently with betadine or some other antibacterial scrub. Let the foamy soap sit on the leg for 15 minutes, then rinse well and pat completely dry with a Turkish towel. At this point you may be able to clip the leg if necessary. Finally it is time to apply your vet’s favorite “scratches remedy.” These are ointments made up of combinations of two or more ingredients. We all have one.
The second important aspect of treating scratches is to refrain from washing the area every day. Remember the bugs love that moisture. Once you have done the initial ichthammol treatment and cleaned up, apply a light coat of the remedy daily, and resist the temptation to wash the leg again. Some cases will need appropriate antibiotic therapy. Horses with white legs that are continuously affected should probably not be in sunlight for long stretches. White skin is more easily irritated by ultraviolet rays. Horses with liver problems may be even more susceptible to the damaging sunlight. Keep animals prone to scratches out of muddy pastures and paddocks. If the lesions get worse and large bunches of them coalesce, the condition is called “grapes”, which is a real mess, and surgery may be indicated.
Vets are usually called to look at scratches as a last resort after a lot of strange potions have been applied to the leg. If not treated effectively and soon, scratches tend to creep up the leg. Long term scratches can lead to a cellulitis which in some cases means a leg that never returns to normal size. My recommendation is to call in your vet at the first sign of any dermatitis of the pastern.
–David A. Jefferson, DVM