EQUINE DERMATITIS PART I: Invasion Of The Crusties
BY JOAN NORTON, VMD, DACVIM | PHOTOS BY DR. CHAD MCGEE B
ut for all the times you have dealt with crusty, oozing and sometimes-itchy skin, how many times have you actually got en to the bot om of the problem? How many times have you diagnosed exactly the cause of the dermatitis so that you can use an eff ective treatment? Or have you,
like the vast majority of horse owners, seen a skin disease and reached for the anti-fungal treatment du jour, whatever spray, cream or oint- ment is fi lling the shelves at your tack shop this year? Sometimes it works, sometimes it doesn’t and every time we are leſt frustrated by the whole process. One of the biggest roadblocks preventing proper treatment of
dermatitis in horses is a lack of diagnosis. While we all think we know what scratches and ringworm look like, visual diagnosis of dermatitis is rarely correct. Many times we could be wasting precious time and money on the wrong treatments. In order to know the cause of your horse’s skin woes, you and your veterinarian must work together to identify the causative agent. Having a complete history is very impor- tant, and you should be prepared to answer some specifi c questions about your horse and his skin: When did it begin? What parts of the horse are aff ected? Is the horse itchy? Is this a seasonal occurrence? Are other animals or people aff ected? Have there been any changes in the environment or diet? Is this horse on any medications or nutritional supplements? And most importantly: what treatments have you already tried?
68 | June 2013 •
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YOUR HORSE’S PROBLEM MAY BE MORE THAN SKIN DEEP
When you and your veterinarian evaluate a horse with skin disease,
it is important not to have tunnel vision and just look at the skin. T ere are several infectious, metabolic and even cancerous diseases that cause dermatitis secondary to the main problem. In order to catch these cases, we must fi rst perform a thorough and general physical examination to rule out systemic illness as the cause of the skin disease. T e most important aspect of diagnosing dermatitis is the collection of samples for diagnostic tests. Dermatitis is oſt en misdiagnosed when based on appearance alone,
leading to inappropriate treatment and prolongation of the disease. Plucked hairs or a sample of skin cells can easily be collected and evaluated under a microscope for the presence of bacteria, fungus or parasites. If bacteria or fungus is suspected, a culture of the aff ected area should be taken. T is will not only identify the culprit but will generate an antibiogram, a list of antibiotics or antifungals that will kill that specifi c bug. T is information allows you to pick the exact antimicrobial for your horse’s infection. If a skin disease is very severe or has been longstanding and refrac-
tory to treatment, a punch biopsy can be obtained for the most in-depth analysis. A sample of skin (4-8 mm in diameter) is removed with a biopsy tool that works like a very sharp cookie cut er, “punching” out a small circle of the aff ected area. T is tissue can be sectioned, stained and evaluated under a high-powered microscope to see the architecture of the epidermis and dermis, identify infections deep within the skin
What’s causing all of that oozing, scabbing and itching in your poor pony? Here’s what you need to know to stop guessing and start treating
THERE A
IS (OR SOMETHING ICKY) AMONG US? FUNGUS
As the timeless poem reminds us, “April showers bring May fl owers.” But for many horses the wet weather of spring brings more than just green grass and daff odils. Moist weather, muddy fi elds and ever-present dew on the grass can cause severe cases of dermatitis in horses each and ev- ery spring. It can be a nightmare to manage these cases, keep horses from losing hair or miss out on springtime activities because of sores under the saddle or discomfort from swollen limbs.
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