What are Pastern Dermatitis?
There are many reasons that horses may develop dermatitis on the pastern, including infections, persistent moisture, and phototoxicity. The heavy feathering on draft horses such as the Shire and Clydesdale breeds makes them more susceptible to developing the lesions and rashes associated with pastern dermatitis, and horses with lightly pigmented pasterns may also be predisposed. This condition has a number of alternate names, like mud fever, greasy heel, and grapes, and may or may not be accompanied by dermatitis affecting other parts of the body.
Pastern dermatitis is a symptom of several different diseases or disorders and can range from mild crusting to large papillomatous growths on the pastern of a horse.
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Symptoms of Pastern Dermatitis in Horses
This inflammation of the skin in the area of the pastern can develop uncomfortable and unsightly rashes. Depending on the cause of the dermatitis, the rash could include any of the following characteristics:
- Bleeding lesions
- Foul smelling pus
- Granulomatous lesions
- Hair loss
- Oozing sores
- Reddened skin
- Thickened skin
- Wart-like appearance
Pastern dermatitis is more common on the rear feet than the front.
- Mild - The gentlest form of this disorder is characterized by hair loss, dry scales, and insignificant lesions and crusting; it is also known by the names scratches and mud fever
- Exudative - In this type of pastern dermatitis, the crusting and lesions typically ooze and often smell foul; lesions on the pastern often bleed with the exudative form of this disorder, also known as dew poisoning or greasy heel
- Chronic proliferation - Also known as grapes, this type of pastern dermatitis presents with rough thickened skin in the pastern area; the lesions from the chronic version of this disorder may require surgical intervention
Causes of Pastern Dermatitis in Horses
There are several circumstances that can produce pastern dermatitis:
- Allergic reaction
- Bacterial infection
- Consistently wet environment
- Contact with caustic substances
- Fungal infection
- Ingestion of phototoxic plants
Certain physical characteristics may increase a horse’s chances of developing pastern dermatitis. These features can include:
- Feathering on pasterns
- Pasterns that lack pigment
The Clydesdale and Shire breeds appear to be more prone to developing pastern dermatitis.
Diagnosis of Pastern Dermatitis in Horses
The focus of diagnosis when pastern dermatitis is found is the detection of the underlying cause. A visit with your equine veterinarian regarding dermatitis of any sort will begin with a thorough history of the horse. This will include getting as much information as possible about the horse’s diet, medications, and environmental factors. Standard blood tests, including a biochemistry profile and complete blood count, will be evaluated to see if a systemic infection is present and to check and see if there is evidence that an allergy may be the culprit.
The placement of the dermatitis may also help narrow down the underlying cause; in the case of allergies all four feet are more likely to be marked with dermatitis and phototoxicity may be more prominent on areas with low pigment or on the areas most exposed to the sun. A sample of the affected skin will be taken to examine by cutaneous cytology. This microscopic examination will help reveal if mites, fungal infections, or allergies are the cause of the rash. If that does not locate the underlying cause, a biopsy of the tissue will be required for further evaluation.
Treatment of Pastern Dermatitis in Horses
The treatment of the dermatitis will depend in part on the underlying cause of the rash, but certain steps are standard regardless of the cause. Any hair that is in the way will be clipped to help keep the area clean and dry, and the area will generally be cleaned and treated with antiseptics. Any scabs will generally need to be removed as well, for proper healing of the area. This process is not typically pleasant for the patient and in many cases sedation is required to complete this process. Once this is complete, the underlying problem will be addressed as well.
Antibiotic, antifungal, and anti-inflammatory medications will be prescribed for the animal as needed, either orally, topically, or by injection. If contact allergies are suspected, different bedding should be utilized for the patient’s stall. If photosensitivity is contributing to the disorder, It may be wise to keep the horse in a stabled or fully shaded area when the sun is at it’s most intense during the day and pull on socks may be recommended to protect the area from exposure to the sun’s rays.
Recovery of Pastern Dermatitis in Horses
While your horse’s feet recover from the dermatitis, it is critical to ensure that the affected area remains clean and dry. This can mean keeping the horse stabled if there is still dew on the ground, keeping feathers and long hair from the back of the legs clipped short, and making certain that any mud or sweat is washed off with an antiseptic shampoo and is not allowed to dry on the affected area. It is also important to continue any ointments and medications as long as the veterinarian recommends as reoccurrence of pastern dermatitis is common.