Rain Rot Scar

My horse had rain rot this summer, not terrible, mostly under his chest and near his legs only. I noticed a tiny little bump, hard, doesn’t seem to be attached to anything (no root) looks like a rain rot scar. Is this possible?

Rain rot actually tends to affect the back and sides of the horse, where moisture due to rain and sweat tend to keep the skin chronically damp and less resistant to fungal and bacterial invasion. Your horse probably has another form of skin infection, but either way it is unlikely that it is related to the nodule you have recently noticed. This probably a small collagen granuloma (often called nodular necrobiosis). Skin irritation from a bug bite is one cause, and they often also occur under pressure points- mainly in the saddle and girth area. The compression and friction that occurs from tack can rupture the hair follicle, releasing collagen and stimulating a local inflammatory response. I often compare it to an ingrown hair. This causes a palpable lump, which over time may calcify. If the bump is in an area that is becoming rubbed or irritated  I usually have very good results by simply injecting a tiny bit of triamcinolone (a type of light steroid) into the lump, which then goes away after a few days. There are some horses that will develop these lumps repeatedly but they always respond very well to injection if you catch them before significant scar tissue has formed. If the nodule is not growing in size, not painful or ulcerated, and does not get rubber by tack, I would simply keep an eye on it for now.

Melissa McKee DVM

Pigmentation Loss

Can you tell me about pigmentation loss in grey Arabians- is it permanent? can it go back? In a pre purchase is it considered a negative thing?

Pigmentation loss in grey horses usually occurs around the lips, eyes, and genital area. It is seen most frequently in Arabs and horses with Spanish genetics (such as Andalusians) but can actually affect any breed and colour of horse. The condition can appear, expand, and regress spontaneously. It is thought to be caused by the immune system inactivating the pigment producing skin cells called melanocytes, and is generally a harmless cosmetic condition. In some cases it may be associated with other immune-mediated health issues so a thorough physical exam is indicated if this condition is noted. The other consideration is that nonpigmented skin is more susceptible to UV radiation, so the use of fly masks and sunscreen is a good precaution to prevent burning.

Melissa McKee DVM

Erythema Multiforme

One morning these swellings were discovered all over this horse’s body. They were not painful or itchy and there were no signs of distress. What is this condition and what can be done to alleviate it?

This is a special type of hives that is sometimes called “Erythema Multiforme”. The swellings tend to spread outwards and leave a flattened arena in the central area of origin. Nobody knows what causes this particular type of reaction and it often does not resolve with dexamethasone like regular hives do. Affected horses can have occasional outbreaks and the swelling can take several weeks to fully resolve in spite of treatment with several types of medication. Fortunately the condition is not painful or debilitating, but it certainly looks odd!

Mud and Mud Fever Management

How harmful is it for horses to stand in the mud and manure while the snow melts in the spring? What strategies can I use to avoid mud fever etc in a boarding situation? I have rubber mats at the feeder but they are getting swamped.

Some horses are very tolerant of muddy conditions and suffer no ill effects from the dirt and constant wet-dry cycle. Others are less fortunate. Persistent moisture diminishes the protective waxy barrier on normal equine skin, making it more susceptible to mixed bacterial and fungal infections, which once established can also trigger a chronic inflammatory response that causes ongoing problems even if the infection is cleared. Aptly named “scratches” or “mud fever”, it tends to flare up in the spring and fall when mud is the predominant feature in many paddocks and riding rings.
There is little to do with regards to mud around the feeder, other than trying to find the highest and most well drained area to situate it, and moving it regularly when the conditions around it get too wet. In the long run however, the second strategy can be pretty destructive to the whole pasture.
Other than keeping susceptible horses inside or separated into a smaller, drier paddock, the next best strategy is to maintain the best hygiene you can between turnout periods. Application of a water repellent protective cream, such as a zinc-based diaper cream before turnout, followed by gentle cleansing and drying of the heels when the horse comes in will interrupt the cycle of skin saturation and colonization with microorganisms that leads to chronic scratches. Stretchy zip-up coronary band-to-knee boots are available which can perform well at protecting the leg from mud if they are properly fitted, and may be an option with horses who have chronic scratches complicated by sensitivity to UV light.

Melissa McKee DVM

Tail Rubbing

Help! My horse is rubbing his tail out!

This is a really frustrating situation which I can definitely relate to. There’s nothing worse then watching your horse destroy his tail every day. The reason you haven’t found much information about it is that there isn’t much information out there. We know that mane and tail are often both involved and limbs can be affected as well. There is a classic matted, greasy appearance with scaling or crusting in the affected area. The condition is often secondary to some other injury but can also be caused by exposure to skin irritants (chemicals or urine scalding). A primary problem with the sebaceous glands is rare. Other conditions that can mimic seborrhoea are certain immune mediated diseases, rain rot, mange, ringworm etc. Diagnosis is usually based on clinical appearance as biopsy is often unrewarding. Treatment generally involves close clipping of the affected area and shampooing with an anti-seborrhoeic (selenium based) shampoo every 2-3 days. Please do not hesitate to contact our office again if you would like to discuss your horse’s case or rule out some of the other possible conditions.

Michelle Courtemanche DVM

Flaky Skin

I have a thoroughbred gelding, who has what i thought to be rain rot. However I went to check on him today and he was covered in what seemed to be white flakes and dirt all over his neck and other patches on his body,there also seems to be a little bit of hair loss. It looks like really dry flaky skin but I’m not sure.

Rain rot usually appears as matted crusty hair over the topline and quarters that reveal serum and pus when the crusts are pulled off. Serious infections can be quite painful, so it does not sound like this is what is going on with your horse. What you describe could be a range of problems. At this time of year he may have had a mild fungal or bacterial skin infection that results in dandruff-like crusts brushing off. Make sure you look at that dandruff very closely because lice can also appear in this fashion and do not always cause itching. Another possibility is simple dry skin and hair from too much washing or not enough fatty acid in the diet. If this is the case then adding a coat conditioning supplement to his feed and backing off with the soap may be all you need to do. There are some rare but serious medical conditions that can cause profound scaling and dandruff all over the body, so if this condition persists or gets worse you should get your vet to take a look.

Melissa McKee DVM

Chronic Cannon Bone Scab

I purchased a horse in 2008 that had sustained a nasty injury in in 2005 (as a 2-year old). He got wrapped up in electric fence and it dug into the front of his hind right cannon bone. I had the leg radiographed during the pre-purchase exam and the vet said the bone has been affected but was remodelling well and she didn’t expect any problems.

The question I have is with respect to the original cut – irrespective of what I do it still appears to have an active scab on it. I can soften it up and have some of it come off but it always reappears. I don’t really understand why this is still occurring and any suggestions on how to deal with it would be much appreciated.

The dorsal cannon bone is a real problem area for wound healing as it doesn’t have the best blood supply and wounds in this area often involve extensive tissue damage and contamination. Wire wounds in particular are quite serious as they will also cause avascular and thermal necrosis if it wraps tightly around the leg and the horse creates a lot of friction while struggling (no doubt that he struggled if the electricity was on!). The injury sustained by your horse must have gone all the way to the periosteum (the fibrous layer covering the bone) itself, which is why there are roughened areas of bone visible on radiographs. If the tissue and vascular damage is sufficiently extensive, and the wound could not sutured together, it can be impossible for the skin edges to migrate across the area to create an intact surface. In these cases, a chronic fibrous tissue mass called a “keloid” will develop. These scabby, thickened areas tend to be persistent for the rest of the horse’s life and do require a bit of additional management, although they are not particularly painful and are generally well tolerated. It may be possible to surgically excise this old granulation tissue and try to bring the skin edges back together with sutures, but wound breakdown in this area is very common and you may not be any better off in the long run. If you do choose to try to close the gap, several procedures, including skin stretching and grafting may be required and your horse will have to be confined for several weeks with heavy bandages or a cast to provide maximum stability to the repair.

Melissa McKee DVM

Chronic Pastern Dermatitis

My horse has been getting scratches on and off all summer/winter. I have tried a combination of tons of different medications and have found a few that work well but it is very expensive to continue to just treat it every time, and very time consuming.

My horse seems to be the worst in the barn for getting it because he has to wear bell boots on all four feet or he pulls his shoes and his bell boots, no matter what I do rub a little. It usually only affects his 2 back whit feet but this time when he got it it affected all four and he really stocked up. What should I do?

It sounds like your horse suffers from a more complicated problem than simple mud fever/scratches. Occasionally, a horse that starts out with chronic scratches will go on to develop an allergic condition called “leucocytoclastic pastern vasculitis”. Basically, the hypersensitive skin on the lower limb becomes over-reactiv and develops an inappropriate immune response to any kind of stimulus- in fact, UV radiation (sunlight) is a major culprit. The skin becomes painful, and raised oozing crusts develop that do not improve with topical medications and antibiotics. This condition can be diagnosed by your vet based on the history and appearance of the lesions, and it can be confirmed with a skin biopsy. Most cases respond well to a combination of steroids, pentoxyphylline, and topical anti-inflammatory medications. Careful protection from sunlight, especially between the hours of 10 and 4, is critical. This can be achieved by keeping the horse indoors or by applying tall boots/wraps to the legs. You may also want to investigate another style of bell boots, such as the neoprene wrap-arounds or the no-turn style. These may not rub his skin so much. This condition should not be treated without a veterinary diagnosis since the doses of steroids necessary to resolve the condition would also make it difficult for any remaining skin infection to clear up, so they may recommend a course or antibiotics before starting the anti-allergy treatment protocol.

Melissa McKee DVM

Found a Tick on my Horse

While clipping my mare (about 6 weeks ago) I found an old “deflated” dead tick stuck to her chest. I wasn’t really thinking at the time (too much horse hair up my nose…) and just pulled it off (it was later I realized I should have been more careful to get the head of the bug removed). Anyhow, I have noticed a bump where the bug was located (feels like a pimple and has been there since I removed the bug). Doesn’t seem to bother her but I am worried about lyme disease and the possibility that the tick’s head may still be under her skin. Suggestions?

The little lump you can feel is likely just a bit of inflammatory reaction to the bite that has formed a spot of scar tissue. There are indeed deer ticks in the area so your concern is well-founded. The only way to know if he has been exposed to the lyme disease bacteria (borrelia burgdorferi) is to have his titre measured. If she has a high level of lyme antibodies in her circulation, it is likely that some bacteria was transmitted by the tick. If exposure is confirmed, you can treat her with tetracycline/doxycycline. The treatment is fairly prolonged so I would definitely check her titre rather than just going ahead with the medication. People generally take 6-8 weeks to seroconvert (develop a high titre in reaction to infection) so you could check her blood any time now. If you ever find another tick on her (or yourself), put it in a vial and contact the nearest Ontario Public Health Lab for instructions on where to send it for identification and disease surveillance.

Melissa McKee DVM

Reoccurring Sarcoids

Our horse has a big sarcoid on her ankle and it was removed but is growing back. Any suggestions for treatment? A spray or ointment that can be applied daily?

This lesion is most likely a sarcoid, but could also be proud flesh or another type of tumour called squamous cell carcinoma. The only way to know for sure would be to take a biopsy and have the cells examined under a microscope. There is no topical dressing that will remove a mass of this size- and unfortunately sarcoids are very aggressive and do have a high reoccurrence rate even when treated appropriately and aggressively. The best you can do is to repeat the surgical excision, and keep her confined and bandaged (possibly even with a cast) to prevent irritation and proud flesh formation during the healing phase. Since it will be impossible to stitch the skin closed here, you will have to regularly scrape the proud flesh away so the skin edges can close over. This is a very difficult location to manage any type of wound because of the tightness of the skin and constant motion over the joint, but taking those extra steps may improve your outcome the second time around.

Melissa McKee DVM