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You know how the old saying goes, “April showers bring May flowers and what do May flowers bring?”  SCRATCHES!!! Yes, its that time of year again, when the weather gets warm and the fields get muddy and your horses start to develop these crusted, irritated, painful lesions on their pasterns. It is one of the most common questions posed to online equine forums and when you plug “scratches treatment” into Google you get 13,200,000 results! While I will admit there is often “more than one way to skin a cat,” as they say, I also believe that if there a hundred different (and often conflicting) ways to treat a problem, it’s probably because we just haven’t figured out the right way yet.
Equine Pastern Dermatitis (EPD), aka “scratches,” “greasy heel,” or “mud fever” is a skin disease of the lower limbs. Most commonly seen on the hind limbs, the dermatitis affects the backs of the pasterns and occasionally moves to the front of the limb. Draft breeds and draft crosses with feathers on their distal limbs and horses with white socks  (ie: unpigmented skin) are predisposed to this condition. It is often seen in horses in muddy paddocks, rough prickly pastures and unsanitary condition, due to the high Generally the overall health of the horse is unaffected but severe cases can cause distal limb edema (swelling) and significant lameness.

The exact cause of EPD can be different in each case, but the pathogenesis (which is not entirely understood) is most likely as follows: a small break in the skin allows bacteria in (unpigmented skin is more delicate, and prickly fields more abrasive) and horses in mucky conditions or with long feathers that trap dirt, heat and moisture cannot clear the infection on their own.  There will be pain and swelling with crusted lesions. If not treated properly fissures and a foul odor may develop. In draft horses we sometimes see granulomatous growths of inflamed tissue at these sites.
The causative agents are usually bacteria including, Staph. aureus or Dermatophilus congolensis. There can occasionally be a fungal component and horses infected with mites or lice are at risk for developing infection where the parasites break the skin. While the diagnosis is often made just based on clinical signs, the only way to truly know what’s causing the infection is to have your veterinarian perform a culture and in some chronic cases a biopsy is required.
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While there may be a million and one creams, ointments and sprays out there to fix this problem, the mainstay of treatment should always be to remove all the scabs (another warm moist place where bacteria love to hide) and clean the area thoroughly and often. Clipping the hair short (with a 40# blade) will help getting down to the skin with cleaning and any topical treatments. Clipping, scrubbing and picking all the crusted areas off can be a very painful procedure and many horses have to be sedated by your vet in order to do a proper job. So be safe, especially because you will most likely be working on the hind legs!
Once the scabs are removed and the area is all suds up with an anti-septic solution such as 2% chlorhexidine, povidone iodine or benzoyl peroxide, I like to let the area sit for 5-10 minutes. This give the anti-septic plenty of “contact time” to kill the bacteria. After you rinse the cleanser off completely (dried soap can be irritating and itchy) the leg must be dried. And I mean really dried, not just wipe the excess water off with my hand like a human sweat scraper, or giving it one swipe with an already damp towl. The leg needs to be REALLY dry. For those of you with feathered horses who can’t bear the thought of clipping their lovely locks (or can’t for the summer show season) I recommend a hair dryer on a low setting to help really dry off the leg.

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The next part is where it gets confusing. Ointment or no ointment? To wrap or not to wrap? Systemic anit-biotics or no? Unfortunately we may not have the perfect answer just yet. Anti-biotic creams, or sprays can be applied twice daily to aid in fighting the infection. I like to stay away from petroleum-based ointments, in favor of creams or sprays. These Vaseline like substances water resistant and can be very difficult to completely clean off so that your scrub can reach the skin the next day. The only way to know what topical treatment will really work is to know what bacteria you are dealing with, and for that you must do a culture. Horses with lots of swelling in the lower leg or that have open fissures may benefit from a bandage but I do worry in many cases that bandages will just trap in dirt and moisture. The vast majority of cases do not require systemic antibiotics but in some cases we will treat with a course of oral or injectable medications. Obviously, you must consult with your veterinarian before beginning treatments. I think that all horses benefit from (and appreciate) the use of anti-inflammatories such as Bute or Banamine. Again, check with your vet for appropriate dosing.

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So to review, EPD is an infection in the skin (mainly bacterial, maybe fungal) secondary to breaks in the skin (due to delicate skin, rough pastures, mites/lice or normal wear and tear) that develops in wet, muddy and dirty conditions. Treatment includes clipping, cleaning and drying the affected area at least once a day, then apply the anti-microbial cream or spray du jour and keep your horse as clean and dry as possible. It’s a daunting task and may sound impossible, but the diligent committed owner should be able to get on top of a case of scratches.

 

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