Hi Cherry,

We live in central BC (3 hours NW of Prince George). Our horses are on grass pasture but in fall they naturally move into the aspen and undergrowth for grazing ("bush pasture"). During this time our horses are starting to develop their winter coats. Even in dry falls at least one of our horses develops scabs all over their body. Sometimes they develop while still on pasture and sometimes within a day or two of returning in.

The scabs are very similar to those in rain rot (pus that tightly binds the hair together and eventually the hair in that spot falls out and if removed are damp at the base) but are not contained only on the horse's topline.

This year I had one horse that got them over her entire body with heavy concentrations on her lower girthline and abdomen just in front of her flank. Usually there are large concentrations under the horse's jaw, on the sides of their barrel and on their rump. Our falls and winters are often "cold" (-38C here for a good part of December) so bathing and treatment with any liquid medication is nearly impossible. Our sparse coated appy's seem to be more prone than our long haired ponies (who get regular old super dry skin -- luckily they love flax!) although about ten years ago I had a thick coated Saddlebred X that would get a real whopping round every couple of years. The horses are regularly wormed and are in otherwise excellent health.

The local vet (not that familiar with horse ailments) has suggested it is an allergic reaction but treatment with antihistamines hasn't stopped the formation. This year I'm hearing people say they think it is from eating alsike clover but we have very little clover on our property and there is no photosensitivity or extra damage to white areas (which I've seen in horses that have experienced long term exposure to alsike and once on a horse that was on a ration too rich in protein). I generally remove all the scabs once they are starting to dry up and they don't reappear (until the next fall or sometimes not for a year or two). Any idea what this might be and suggested treatment?

PS I received your Almanac for Christmas. I love it. I've been using 101 Arena exercises for years when teaching Pony Clubbers/4Hers and have purchased your books as awards for the kids. Thanks for providing materials that are clearly written enough I can recommend them to new horse owners and in depth enough that I recommend them to upper level PCers -- it's hard to find that combination! Thank you!

Lisa

Hi Lisa,

Happy New Year and I'm glad that you find my books useful for your students !

We have had a very similar (if not identical) condition on some of our pasture horses in the fall. We live in a semi arid (15 inches of rainfall per year) section of the Colorado foothills. You mentioned that it occurs in even dry falls. Same here and I've thought, "Well this can't be rain rot - it is too dry here."

But first a definition:

Rain Rot (also known as rain scald or dermatophilosis) is caused by a bacterial infection. The bacteria (dermatophilosis congolensis) live on the skin and when the skin is stressed in some way such as from excess wetness, extreme humidity, heat, abrasion (metal or hard plastic curries) or by biting insects, the bacteria germinate and create a network of minute tentacles that penetrate the skin and cause inflammation, pus, and then scabs.

Classic rain rot is usually associated with warm, wet environments such as would be found in Florida.

Our veterinarian said that the condition (that you describe and) our horses get is a variation of rain rot but that to be sure exactly what organism was causing it, a laboratory test would need to be done - either looking at a scraping under a microscope or culturing a sample and incubating it.

He said that the bacteria was opportunistic and that it was always present. Whether it is present on a horse's skin or in the soil has been widely debated but I know of no know research that proves which is true one way or another.

Opportunistic means that the bacteria is always present, waiting around until conditions are perfect for their proliferation. The perfect environment for dermatophilosis bacteria are dirty, damp and dark conditions.

During the fall, whether our horses are on pasture or in pens, are blanketed or not, some horses tend to get the bumps while others don't. I used to think it was the horses that were allowed to roll on pasture thinking they deposited the bacteria from the soil into their coats. As the winter coats grow in the early fall, they create an ideal environment for the bacteria. Inside the fall/winter coat, there is warmth, moisture from body respiration and darkness.

In addition, in our part of the country, biting flies, gnats, midges and so on flourish in the fall. In fact, we have few flying insects UNTIL the fall. Biting insects have been implicated as a cause of in this condition, and in our case, since we don't have the usual factors of wetness, heat, or humidity, the condition manifests differently than classic rain rot. Classic rain rot can have an almost greasy quality while the type we get, and sounds like your horses might have, is dry and crusty.

I've never heard a specific name for this "dryland" variation.

As far as prevention, I've experimented over the years and here's what I've found. If I give a particular horse a bath at fall shedding time, which is late August here, so that the horse is positively, absolutely squeaky clean and rinsed very thoroughly and then keep the horse in a waterproof breathable sheet or blanket through the fall, there is a 95% chance that the horse will not get a single bump on his body. He may get a few on his legs, but as long as he is kept clean and protected from insect bites, the bumps do not appear on the body.

But put a sheet on an unbathed horse in the fall and within days or weeks, that horse could be covered from withers to tail and from topline to underline with hundreds if bumps and scabs. The blanket helps create an ideal incubator.

Prevention includes keeping a horse, his blankets, and grooming tools clean. I've found vacuuming long winter coats is helpful. During fly season, provide fly protection.

Read more about that here Fly Control

As far as treatment once the scabs have appeared, its not a pleasant or pretty procedure as you know. I've found that certain barn combs are the best for removing the scabs, especially if the hair is fairly long - but only if the scabs are ready to fall off on their own and have loosened somewhat already. Follow with a spritz of an antimicrobial solution or a dab of antimicrobial cream rubbed into the bare spots. Keep all grooming tools and gloves separate and wash them often with medicated soap.

Best of luck,