Spotting Skin Problems Early

Use this reference guide to identify your horse's skin troubles and decide what to do about them. By Matthew Mackay-Smith, DVM for EQUUS magazine.
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Use this reference guide to identify your horse's skin troubles and decide what to do about them. By Matthew Mackay-Smith, DVM for EQUUS magazine.

Even horses who receive the best of care may develop the occasional skin problem. There's just no avoiding the host of bacteria, fungi, viruses and insects that can lead to lumps and bumps, scurfy scabs, itchiness and hair loss.

In most cases, equine skin troubles are minor and require nothing more than a thorough cleansing and the application of an over-the-counter topical remedy. Nonetheless, these conditions are generally itchy, annoying or even painful for horses, so the more promptly you can recognize and address them the better for all concerned.

To help you, we've included a brief profile of some equine problems that you are likely to encounter, along with advice on how to treat and prevent it.

When in doubt, of course, you'll want to call in your veterinarian for a diagnosis as well as guidance in treating the condition.

Warts

(also known as viral papillomas)

  • What you see: raised, pinpoint-to pea-size globular bumps. Warts are typically clustered around the muzzle and lips but sometimes appear on the eyelids and genitalia.
  • Is it contagious? Yes.
  • Cause: The papilloma virus causes warts. It is spread both through direct contact and indirectly via shared feed tubs, water containers, scratching posts, grooming supplies and other care items.
  • Pertinent facts: Most common in horses younger than 18 months old, warts can be found among horses up to 3 years of age. After that, they have usually built up an immunity to the papilloma virus.
  • Treatment: Warts disappear on their own within two to three months, but squeezing or scraping away one or two of the larger growths may stimulate the body's immune system and provide a quicker resolution. A single outbreak of warts confers lifetime immunity except in the rarest of cases.
  • Prevention: Should a horse in your barn contract warts, take measures to prevent the virus from spreading: Isolate the animal from other young horses, and use separate water and feed containers, grooming supplies and other horse-care items.

Scratches

(also known as pastern dermatitis, greasy heel or mud fever)

  • What you see: red, irritated skin with crusted, raised scabs just above the heels of both hind legs, or rarely, on a single leg or the forelegs.
  • Is it contagious? No, but it's usually complicated by bacterial infection.
  • Cause: Scratches starts as chapping that is generally brought on by a cycle of alternating wet and dry weather conditions common in late winter and spring. Once the skin becomes cracked and sore, however, bacteria, mites and/or plant irritants often complicate the situation.
  • Pertinent facts: Scratches almost always occurs on both hind legs, below and behind the ankle. If scabs appear on only one hind leg or on a front leg, consider the possibility that you're dealing with an injury rather than pastern dermatitis.
  • Treatment: Areas affected by scratches are often very tender, so be especially careful when working on or around them. Start by washing the affected spot with warm water and shampoo. Once the area is dry, gently clip the hair around the scabs and apply Desitin, ichthammol, petroleum jelly or another lubricating wound ointment sold at pharmacies. Reapply the ointment every day or so until all the scabs loosen and fall away. NOTE: Avoid repeatedly washing the leg, which will encourage more chapping. If the treated area becomes dirty, use a clean cloth to wipe off the soiled ointment and reapply a fresh coat.
  • Prevention: Mud, which harbors a variety of bacteria, and moisture are the main culprits in aggravated scratches. For example, the condition is common in draft horses with feathered lower legs; the long, thick hairs trap moisture, which softens and weakens the skin and allows bacteria or fungi to gain a foothold. If your horse is susceptible to scratches, do your best to keep him in a dry environment during the scratches season, winter or spring in most climes. Clipping excessive lower leg hair, particularly on a draft breed or draft-cross, may minimize the risk of scratches or make treatment easier should the problem develop. Finally, it may help to keep a protective coating of ointment on the heels of chronic scratches sufferers.

Ringworm

  • What you see: circular, raised hairless patches that may be scaly and crusty.
  • Is it contagious? Yes.
  • Cause: Several species of fungus can cause ringworm. One of the most common is Trichophyton equinum, which is spread from horse to horse. Some species, such as Microsporum gypsum, are found in the soil, while Microsporum canis, a rare cause of ringworm, can be carried on the hair of cats and dogs. Ringworm is spread through direct contact or through shared grooming supplies or other care items. In most cases of ringworm, fungi invade the skin through scrapes, abrasions or other minor breaches in the surface.
  • Pertinent facts: Ringworm can affect any part of the body but lesions are usually found on the face, neck, chest, shoulder or on the girth area (known as girth itch). Ringworm infection may initially cause the hair at a site to stand erect before it becomes noticeably affected. The lesions, which tend to be grouped in clusters, may be red and scabby but are usually not itchy. Ringworm is zoonotic (transmissible to people) so wear gloves when handling a horse with the condition.
  • Treatment: If left untreated, ringworm will go into spontaneous remission within about three months, but most people treat horses to speed healing and avoid contagion. Talk to your veterinarian about the best option. If an outbreak occurs at your barn, you may want to do a culture to identify the organism at work. Regardless of the fungus involved, you'll want to avoid treating ringworm with creams or lotions containing corticosteroids--inflammation is one of the body's natural fungus-fighting mechanisms. Instead try one of the following common treatments: Lime sulfur (Lym Dyp) spray or solution is an effective, nontoxic treatment, but it does carry a strong "rotten eggs" odor. For small or localized lesions, products containing chlorhexidine or miconazole--a common ingredient in athlete's foot medications--also have been recommended. Several antifungal sprays and shampoos can also be purchased at tack shops and through catalogs. Iodine (tincture of iodine) has been used to treat ringworm but is not very effective and it can cause severe irritation.
  • Prevention:Because ringworm is highly contagious and fungal spores can remain in the environment for months or even years, disinfect all tack, blankets, brushes, stall walls and anything else that might have come in contact with infected horses. Keep separate grooming supplies for each animal. If a single horse contracts a severe case of ringworm, talk to your veterinarian about preventive treatment baths for all of the horses in the barn.

Sweet Itch

(also known as equine insect hypersensitivity, summer itch, summer eczema, Queensland itch)

  • What you see: hairless patches and red inflamed skin at the root of the mane and tail as well as on the face, neck and belly, where the horse has been rubbing incessantly.
  • Is it contagious? No.
  • Cause: an allergy to the saliva of biting midges, gnats, culicoides or no-see-ums, which feed on horses. The bites cause intense itchiness, which leads the horse to incessantly scratch the affected area, rubbing away hair and damaging the skin.
  • Pertinent facts: Sweet itch occurs only in the late spring and summer when insects are present; during the winter months the skin heals and the hair grows back. However, sweet itch tends to worsen from year to year, so that horses become itchy earlier in the season, and it is provoked by fewer bites.
  • Treatment: Antihistamines can help a horse in the early stages of a sweet itch outbreak, but once he has become sensitized to insect bites, he will likely need oral or topical steroids to stop the cycle and anti-inflammatory drugs to control swelling and ease discomfort.
  • Prevention: The best approach is to limit the exposure of susceptible horses to biting insects. This requires keeping them indoors when the species responsible for the reaction tend to feed: from two hours before dusk to two hours after dawn. For stabled horses, place a fan in front of the stalls to blow the gnats away. It also helps to liberally apply insect repellent and keep horses covered with scrim sheets and fly masks.

Hives

(also known as urticaria)

  • What you see: raised welts and flat-topped and steep-walled bumps of varying sizes and shapes.
  • Is it contagious? No.
  • Cause: an acute allergic reaction triggered by agents that are inhaled, consumed, injected or come in contact with the skin. Instigators include but are not limited to vaccines, systemic or topical drugs, plants, topical sprays, pollen, or insect bites or stings. In many cases, the cause of a hives episode is never determined.
  • Pertinent facts: Hives occur when the mast cells within the skin rupture, causing the smallest blood vessels (capillaries) to leak serum, which pools within the skin. Hives welts appear rapidly and may be tender to the touch or mildly itchy.
  • Treatment: Hives usually disappear on their own within a few hours to a day and a half. Steroidal medications may be necessary if hives are related to a severe allergic reaction--a Red Alert situation that may be accompanied by difficulty breathing and/or severe diarrhea. In this case, contact your veterinarian immediately.
  • Prevention: You may never know what caused an isolated hives outbreak, but if the problem reappears, ask your veterinarian to help you identify the underlying cause.

Photosensitivity

  • What you see: reddened skin and crusty, raised scabs.
  • Is it contagious? No.
  • Cause: sun exposure along with other complicating factors. Photosensitivity almost exclusively affects pink skin, which lacks a dark pigment called melanin that protects against sunlight. Primary photosensitivity occurs when a horse consumes high levels of photodynamic agents--found in alfalfa, clover, bishop's weed and a variety of other plants--which overwhelm his system and damage his skin when exposed to the sun's ultraviolet rays. In secondary photosensitivity, a horse with a damaged liver
    ingests normal levels of photodynamic agents but his body cannot break them down properly.
  • Pertinent facts: Photosensitivity lesions can appear on any area of the body with pink skin, most often the muzzle and face and white ankles or pasterns on the lower legs. The acute lesions begin as purplish blisters that weep or slough away and scab over. Affected areas are sharply painful to the touch.
  • Treatment: If you think your horse has photosensitivity, contact your veterinarian. He may prescribe topical or oral steroids to reduce inflammation, as well as Banamine or bute to keep your horse comfortable. He may also test your horse's liver function for signs of damage.
  • Prevention: If you know your horse is susceptible, keep him stabled during the daytime and limit his exposure to direct sunlight. If your pasture contains plants that trigger photosensitivity, you may need to move your horse to another field.
    Horses who suffer photosensitivity on the lower legs benefit from being turned out wearing shipping bandages or boots.

Rainrot

(also known as dermatophilosis, rain scald or mud fever)

  • What you see: gray/white scabs clustered along the back and hindquarters, leaving patches of hairless skin.
  • Is it contagious? Yes.
  • Cause: A microorganism called Dermatophilus congolensis invades the skin and hair follicles, causing scabbing and hair loss. Moisture and skin damage (usually from prickly vegetation, biting flies or ticks) are the two most significant contributing factors. The rainrot organism is attracted to low levels of carbon dioxide, which is released by the damaged skin. Wet conditions facilitate the dormant organism's activation, which is why many horses develop rainrot along the topline and rump--following the rain runoff pattern.
  • Pertinent facts: Rainrot commonly appears on the head, legs, back, rump and hindquarters. Acute rainrot most often surfaces on the back and hindquarters where the waiting organism is activated by moisture; in the early stages of rainrot the skin may feel hot to the touch and the hair may stand straight up before scabs begin to form. Horses do not build up an immunity to rainrot and may get repeated cases. Chronic rainrot occurs most often on the lower legs, particularly among horses standing in tall, dewy pasture. Some geldings also develop rain-rot on the hind cannon bones from urine splash.
  • Treatment: Without treatment, the horse's immune system will eventually overcome the rainrot organism, but most people try to hasten the process. Scabs can be curried off with a soft-toothed currycomb, but it is not unusual for tufts of hair to be shed with them. Sometimes the removal of scabs is painful and the skin is bleeding or pussy beneath; if so, soften them with a greasy ointment before trying to remove them. It has been suggested that some animals are chronically infected carriers of the organism, so when removing scabs, be sure to sweep them up to reduce contagion. Bathing with povidone iodine or chlorhexidine shampoo can help resolve more extensive cases of rainrot. Also, a variety of topical treatments for rainrot are sold through tack stores.
  • Prevention: Daily grooming reduces the incidence and severity of the condition but is not guaranteed to prevent it. If you notice the telltale upright hair follicles that indicate an infection is taking root, bathe your horse with povidone-iodine or antifungal shampoo and talk to your veterinarian about administering penicillin--this is the time when antibiotic injections are most successful in arresting rainrot.

This article originally appeared in the September 2005 issue of EQUUS magazine.