Mud Fever in Horses: Signs, Treatment and Prevention

Mud fever is a painful inflammation of the skin on a horse’s lower legs, usually the back of the pasterns and heels, which shows up as scabs, sore or weeping skin and sometimes swelling. It is most common in wet, muddy months, and the best approach is to keep legs clean and dry, avoid scrubbing, and ask your vet to confirm the cause early, because several different conditions look the same.

What mud fever is

Mud fever is the everyday name for pastern dermatitis. You may also hear it called cracked heels or greasy heels. It most often affects the pastern, the sloping area between the fetlock and hoof, and the heels, and white legs are affected more often than dark ones.

The name covers a group of problems rather than one disease. Prolonged wet weather softens the skin, and mud and grit rubbing on it cause small breaks that let bacteria in. A bacterium often involved is Dermatophilus congolensis, which also causes rain scald on the back, but Staphylococcus and other bacteria can be involved too. Other causes include:

• chorioptic mange mites, which are especially common in heavily feathered breeds such as cobs, Shires and Clydesdales
• fungal skin infections
• photosensitisation, a reaction to sunlight in unpigmented (pink) skin, sometimes linked to certain plants or to liver disease
• pastern vasculitis, an immune-mediated condition that also tends to affect white legs.

These need different treatment, which is why a vet’s diagnosis matters. Sores found only on pink skin, or that flare up in sunny weather or when the ground is dry, may point to something other than simple mud fever.

The British Horse Society describes mud fever as non-contagious. Even so, it makes sense to keep separate brushes and towels for a horse with sore legs, as you would for any skin infection.

Signs to look for

Check your horse’s lower legs every day in wet weather, including under feathers, which can hide early scabs. If your horse is happy for you to do so, part the hair gently and look closely at the skin around the heels. Stop if they pull away or seem sore.

Early signs are small crusty scabs, matted tufts of hair and patches of broken, pink or damp-looking skin. As it progresses you may see hair loss, raw areas, a creamy, yellow or green discharge under the scabs, heat, swelling and pain when the leg is touched. Severe cases can cause lameness.

Mud fever can be very painful even when it looks minor, and scabs can hide infection underneath. Don’t pick or scrub them off. The British Horse Society advises that scabs shouldn’t be forcibly removed unless your vet advises it, and notes that removing them can be so uncomfortable that sedation may be needed.

When to call the vet

Contact your vet as soon as you suspect mud fever, so the cause can be confirmed before you start treating it. Call the same day if:

• the leg is hot or swollen, especially if the swelling spreads up the leg
• your horse is lame or won’t put weight on the leg
• your horse seems unwell, dull or off their food
• there is a wound nearby, or the area is spreading quickly.

The Horse Trust warns that untreated mud fever can lead to a deeper infection or cellulitis, a spreading infection of the tissue under the skin, which needs prompt veterinary treatment. Get back in touch with your vet if the skin doesn’t improve with their plan or keeps coming back.

If your horse stamps, rubs one leg against the other or bites at the legs, mites are a likely cause, particularly in a feathered horse. Mite infestations need their own treatment, and treating for mud fever alone won’t clear them.

How a vet may treat it

Your vet will examine the skin and may take scrapings or swabs to look for mites, bacteria or fungi. If the horse has white legs and the problem doesn’t fit the usual pattern, they may also consider photosensitisation or vasculitis, and in some cases recommend blood tests or a skin biopsy.

Treatment depends on the cause and how severe it is. It often includes clipping the hair around the area so the skin can be cleaned and dried, gently washing with a dilute antibacterial wash in warm water, drying thoroughly and applying a suitable cream. Your vet may advise how to soften scabs so they come away gently. Antibiotics, anti-inflammatories or mite treatment may be prescribed when needed. Follow the plan closely, including how often to clean the area and when your horse should be seen again.

Don’t use leftover creams, strong undiluted antiseptics or medicines prescribed for another horse. Damaged skin is easily irritated, and the wrong product may not treat the real problem. Don’t give pain relief unless your vet has prescribed it.

Reducing the risk in wet weather

You can’t make every winter field dry, but you can cut the time your horse spends standing in deep mud. Fence off the worst areas, rotate paddocks where you can, and put hardcore or other firm standing around gateways, troughs and feeders, where mud builds up fastest. Keep stable bedding clean and dry.

How you deal with muddy legs matters. The British Horse Society advises against washing legs every time a horse comes in. Instead, let the mud dry and then brush it off gently with a soft brush. If you do need to wash the legs, use warm water and dry them thoroughly with a clean towel. Frequent washing, especially when legs are left damp, is a recognised risk factor. In heavily feathered horses, ask your vet whether clipping the feathers would help you keep the skin clean, dry and easy to check.

Barrier creams can help some horses, but they should only go on clean, dry skin, never over mud or sores. Well-fitting turnout boots may help, but check underneath them daily, as rubbing or trapped mud can make things worse. Treat small cuts and overreach injuries promptly, since broken skin gives bacteria a way in.

If your horse gets mud fever every winter despite good management, ask your vet whether something else is involved. Mites, photosensitisation and a weakened immune system, for example from Cushing’s disease (PPID), can all make the skin harder to keep healthy.