Mud Fever - Pastern Dermatitis

July 24, 2019

Temperamental Victorian weather provides quite a few issues for both horses and their

owners. One of the more frustrating problems the presents during the wet winter months is

pastern dermatitis or commonly known as mud fever, greasy heel and other colloquial

terms.

The condition is usually caused by a bacteria called Dermatophilus congolensis although

other bacteria, fungi and yeasts do contribute. This same bacteria also causes rain scald

along the horses back and rump. Many bacteria live on normal healthy equine skin and will

cause an opportunistic infection when the skin becomes traumatized. Wet sandy paddocks

are ideal conditions for this to occur but can happen whenever the pasterns receive

abrasions and are left wet for too long such as frequently working in a sandy arena,

excessively washing the legs without drying and ill fitting boots.

It usually starts with generalised swelling of the affected area, redness and inflammation

and scaling of the skin. This then progresses on to moistness, matting of the hair and

scabbing or crusting. These scabs are painful, often located in the horizontal folds behind

the pastern and harbour the offending bacteria beneath. Swelling of the lower limb is

common as well as some degree of lameness in the more severe cases.

Pastern dermatitis usually affects the hind limbs and will often have a predilection for

unpigmented skin. Feathering on the legs of some breeds may provide a warmer and more

moist environment that the bacteria likes to grow in but these horses might also have an

infestation of mites that cause itching and the horse may eventually self traumatize.

There is no universal cure for mud fever as there may be a variety of microorganisms

present as well as other concurrent conditions. In uncomplicated scenarios, removing the

horse from wet pasture is the first step and ensuring they are on non irritating footing and

bedding.

Horses with heavy feather may need them removed partially to access the lesions

but clipping horses with pastern dermatitis down to the skin is not recommended as the

clipper rash will provide bacteria with an opportunity to invade the deeper layers of the

skin.

The main principle of treatment of treatment is washing with a dilute solution of

chlorhexidine for example, removing any scabs that come away easily and drying the leg

extremely well. Use clean towels and a hair dryer can help ensure the leg is fully dry. Only

wash the legs every 2-3 days but apply topical antibiotic ointments daily e.g. dermapred or

flamazine.

Some horses may require pain relief if the heels are particularly cracker and some

advanced cases may become systemically ill or develop a cellulitis which require antibiotics.

Be aware that a handful of other conditions may resemble or predispose to mud fever and

these should be considered in particularly stubborn cases. For example, photosensitization

from being exposed to certain plants or drugs or liver damage often presents as sunburnt

crusts on white areas of the body. Some immune mediated conditions can cause similar

lesions.

If you have any further questions please get in touch with any of our vets.

You can call our office on 03 5975 6586

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