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Mud Fever

Mud fever is a form of pastern dermatitis and specifically refers to a bacterial skin infection usually present on the lower limbs of horses. The majority of mud fever infections involve a bacteria called dermatophilus congolensis but they can involve different or additional secondary bacteria. The bacteria are found on the surface of all horses’ skin normally but cause the infection if the usual protective skin barrier is breached. It is commonly seen during wet seasons from mud or long wet grass due to prolonged exposure to moisture which causes the loss of the skin barrier allowing the bacteria to penetrate deeper.

Symptoms

The most common sign of mud fever is scabbing usually in the heel bulbs and on the pastern and fetlock of one or more limbs. There can also be hair loss, sore red-looking skin, swelling and lameness. Usually when the scabs are lifted there is raw sore looking skin underneath as well as pus sometimes.

Diagnosis

Clinical examination is often sufficient alone to make a diagnosis. Swabs of the infected skin underneath scabs can culture the bacteria involved for more targeted therapy if indicated. Sometimes it is important to rule out some other disease which can look like mud fever such as exudative pastern dermatitis, chronic proliferative pastern dermatitis, pastern leukocytoclastic vasculitis, leg mites and pemphigus.

Treatment

Mild cases with no swelling of the limb or lameness should resolve with topical treatment including:

1. Washing the affected area with warm water containing diluted hibiscrub and removing scabs which will come away. The bacteria live underneath the scabs so removing the scabs exposes them to the elements and hibiscrub treatment killing the bacteria. It is important to leave the hibiscrub on for at least 5 minutes before rinsing to act and then thoroughly dry the limbs after washing.
2. Topical medicated creams – either just antibiotic or antibiotic and steroid containing.
3. Change of management to allow full resolution – keep the horse off wet land whilst the mud fever clears up. This may involve a period of box rest with exercise from the box if the land is very wet.

More severely affected cases will require the above plus some systemic medication including:

• Antibiotics – may be indicated if there is a secondary cellulitis (the infection has gone deeper than the skin causing pain, swelling and possibly lameness).
• Pain killers – some mud fever infections are painful especially if there is secondary cellulitis and it can even make horses lame therefore a course of oral anti-inflammatory pain-relieving medication is often required. An improvement in comfort will also hopefully allow safer and more pleasant topical management as the horse will be more amenable.

Prevention

Attempts to prevent mud fever should be made if the conditions are wet and particularly if the horse has experienced it before. This involves helping the skin to maintain its healthy barrier by allowing breaks from the wet where possible (such as bringing in the stable for periods of time), using barrier lotions or powders, drying the limbs as often as possible, if washing mud from limbs ideally use warm water and dry them afterwards, treat any small cuts on the limbs quickly and act quickly if some scabs start developing.