Dermatophilosis specifically is an infection by the bacteria Dermatophilus congolensis. However, when an animal becomes infected, frequently there are multiple organisms that can be isolated after a very short period of time and a generalized bacterial dermatitis results. Given the right environment, sometimes a fungus may cause an additional infection and create a condition called Dermatophytosis. This can be confusing, but since treatment tends to be similar for all of these, we usually just go straight to treatment.

Dermatophilosis is usually seen over the back, hindquarters, back of pasterns, or on the hind cannons. The disease is frequently worse over white skinned areas.  Lesions can be small dry crusts that are easily removed with grooming or rubbing, or they can be larger crusts with yellow-green or gray colored pus underneath them. Early in the infection, removal of crusts or touching the horse in the affected area can cause pain. Hair attached to the crusts tends to fall out easily as the crusts are removed, producing the typical “paintbrush” look that characterizes this disease. Rain soaked skin, or skin that is broken, irritated, or damaged by insect bites or trauma is more likely to develop the disease.

Three things need to be present for the disease to manifest.  First, the organism needs to be on the animal (dirty).  Second, moisture (not a problem here in Oregon), and third…heat.  The animal’s body heat actually is enough to make the infection take off, and with long hair trapped under blankets or standing in bedding can be enough to allow for the infection to take off.

Dermatophilosis is contagious and can spread to other animals and people by contact with the crusts or by shared tack and grooming kit.  Treatment is usually aimed at removing the crusts gently (MTG works well) and washing the skin with an antiseptic shampoo such as iodine or chlorhexidine.  Just as important, the animal must be rinsed very well as any scabs that are just rinsed to a lower part of the leg can re-infect.  After bathing, a salve or cream can help reduce the sensitivity of the skin.

Antibiotics are frequently necessary to help control the infection if it gets deep enough in the skin.  Sometimes anti-fungal medication is also used.  Transmission between animals and people can be avoided by not sharing tack or grooming supplies, and disinfecting all equipment that comes into contact with infected horses.  If you are uncertain, please call your vet to have them advise you as to the best course of action.

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Muddy ground can soften feet and can decrease the sole’s ability to absorb concussion, causing bruising of the main structures. Bruises may abscess if bacteria are introduced through the crack or from circulating bacteria in the bloodstream. Penetrating wounds can occur as a result of a horse stepping on a sharp object such as a rock or nail. These may cause a perforation of the sole that packs up or seals over, and an abscess results as a result of contamination. Occasionally a misplaced nail will also result in a foot abscess.

Foot abscesses are commonly seen around the white line area where foreign bodies such as grit penetrate the white line, allowing bacteria to enter the foot.

Signs of an Abscess
Most affected horses show sudden (acute) lameness. The degree of lameness varies from being subtle in the early stages to non-weight bearing. The affected foot may be warm or even hot to the touch, and the digital pulse felt at the level of the fetlock is usually increased.

Treatment
If the horse has a shoe on the foot, the shoe should be removed. Hoof testers are frequently used to find the exact source of pain. The white line may also be lightly pared using a hoof knife to identify any tracts that could indicate the location of the abscess. Once the location of the abscess is known, the vet or farrier can open the abscess to allow the pus to escape (the pus may be grey/black), which will release the pressure and relieve the pain. Antibiotics aren’t given as they don’t reach the abscess through the bloodstream. If your horse is not up-to-date with his/her tetanus vaccination you should let your vet know, as the abscess hole provides a perfect site for tetanus to enter.
After drainage is achieved, the foot is usually disinfected with soaks in either a salt solution (Epsom Salts) or a diluted antiseptic such as iodine. After disinfection, the foot can be wrapped dry or with a poultice. There are a variety of effective solutions on the market, but the key is to keep the foot clean and protected during the healing phase. For pain an anti-inflammatory agent such as Phenylbutazone (Bute) can be used to keep your horse comfortable.

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