by Ashley Stewart BVetMeD MRCVS
Also known as pastern dermatitis or ‘greasy heel’, mud fever is most frequently seen in horses during wet and muddy conditions. It is caused by the bacteria Dermatophilus congolensis, which thrives in these conditions. This bacteria enters the body through cuts, grazes and wet skin before multiplying rapidly in the epidermal skin layers and causing an infection.
Mud fever commonly affects the back of the pastern, causing scabby lesions and inflammation. However the bacteria can also affect the skin over the hind quarters and along the back of the horse, causing a condition known as rain scald.
- Spending a prolonged period of time in mild/damp conditions
- Standing in deep mud
- Constant washing of limbs
- Excessive sweating due to rugging or long-hair coat
- Limbs with lots of feathering are more likely to develop mud fever
- Skin trauma due to cuts and grazes provides an entry point for bacteria into the skin
- White limbs are more prone to infection
- Mite infestation
- Fungal infections
Mud fever is normally fairly straight forward to identify, however diagnosis of the exact cause is not always easy. Your vet may take hair samples, perform a skin scrape or takes samples of the scabs if the cause is not easily identifiable. If the condition is not responding to treatment then your vet may potentially want to perform a full thickness skin biopsy.
This varies depending on the inciting cause of the mud fever, and there is no single effective cure. Treating underlying conditions such as mite infestation or a fungal infection if present is important to allow the skin’s natural barrier to heal.
The fundamental elements of treatment include:
- Stabling the horse
- Prevents the area from getting muddy
- Removes the wet/dry cycle which damages the skin barrier
- Clipping the legs of heavily-feathered horses
- Allows easy visualization of affected areas
- Allows easier removal of scabs and cleaning of area
- Removal of scabs
- Bacteria live in the scabs, so infection will not resolve unless these are removed
- Cleaning of affected areas with warm water containing dilute Hibiscrub
- Softens and removes scabs
- Treats infected lesions on the leg
- Drying of the affected limb with a towel
- Use a different towel for each leg to prevent spread of infection
- Application of a topical antibiotic cream to the lesions
There are further treatment regimes that your vet may use, including systemic antibiotics, anti-inflammatories, mite treatments or steroids.
Prognosis for simple mud fever cases is good, with the vast majority of horses recovering with only the basic treatment regime recommended above. However if there is an underlying condition present, this needs to be treated first to prevent recurrence.
Historically many owners have washed mud off their horse’s legs at the end of daily turnout. However this constant wetting and chilling of the skin can make it vulnerable to infection. Nowadays the author would tend to advise that the mud is allowed to dry on the legs before being brushed off.
Horses with hairy lower limbs may benefit from clipping, particularly if they have long feathers. Not only does this enable diagnosis in the early stages, but it also helps to prevent the skin from becoming cold and moist.
If you are taking your horse for a ride in muddy conditions, then it is sensible to try to waterproof the lower limbs. This can be achieved by using barrier creams. However this should only be done if you are absolutely certain that there is no skin infection present, as otherwise you risk trapping infection in the skin. Alternatively the use of waterproof leg wraps during turnout can help prevent the lower limbs from becoming wet and muddy.