How to Spot and Treat Mud Fever in Horses

What Is Mud Fever, and Why Does It Happen?

Mud fever is the everyday name for pastern dermatitis, a skin infection that develops on the back of the pasterns and, in stubborn cases, creeps up the cannon bone. It is caused by Dermatophilus congolensis, a bacterium that lives quietly on healthy skin but takes hold when the skin's barrier is compromised. Prolonged wetting is the trigger. Waterlogged skin softens, cracks and loses its natural defences, and mud carries the bacteria straight into those tiny breaches.

It is not simply a case of "dirty legs". Plenty of horses live out in mud without a speck of trouble, while others seem to break out at the first hint of a wet November. Thick feathers, white legs, sensitive pink skin and a compromised immune system all make a horse more vulnerable. So does standing in a boggy gateway for hours on end, which is where most of the damage is quietly done.

Spotting the Early Signs

Mud fever is far easier to manage in its first week than in its third, so daily leg checks through the wet months are worth the small effort. Run your hands down each leg, right down to the heel. You are feeling for heat, thickening and uneven patches beneath the hair.

Look out for:

• Small, matted tufts of hair on the back of the pastern, often described as looking like tiny paintbrushes
• Crusted scabs that sit flat against the skin or stand proud in grey-yellow lumps
• Mild swelling of the pastern, sometimes with a little heat
• Cracked, sore-looking skin at the heel or around the ergot
• Shortened strides, reluctance to pick up a hind leg, or sensitivity when you touch the area
• In feathered breeds, a greasy, smelly discharge hidden deep in the feather

Early on, your horse may be completely sound and unbothered. That is the ideal moment to act. If the leg is hot, swollen well above the pastern, or your horse is genuinely lame, this is no longer a straightforward case of mud fever and your vet should be involved.

Why Wet Mud Does So Much Damage

Skin is designed to be dry. When it stays damp for hours, the outer layer swells and softens, and the natural oils that keep bacteria out are washed away. Add abrasion from gritty mud and the small knocks that come with turnout, and you have an open door.

The type of ground matters too. Deep, sucking clay is worse than sandy soil, and a field that poaches around the gate, trough or hay rack concentrates the problem in one spot. Horses with heavy feathering hold moisture against the skin for far longer, which is why traditional cobs and draught types so often suffer. Standing in a wet stable on dirty bedding keeps the cycle going overnight.

Treating It Step by Step

The single most important thing you can do is get the legs clean and, crucially, dry. Everything else follows from that.

• Bring your horse in to a clean, dry stable with fresh bedding. This alone often starts the healing process.
• Clip the hair over the affected area if your horse will tolerate it. Removing the hair lets air reach the skin and lets you see what you are dealing with.
• Wash with a dilute antiseptic solution recommended by your vet, using warm water and a soft sponge. Work gently; scrubbing hard spreads infection and makes the skin sorer.
• Soften and lift the scabs. A warm, wet poultice or a thick layer of a soothing ointment left for a few hours will loosen them. Never pick dry scabs off — you will tear the skin and set yourself back days.
• Dry the legs thoroughly with a clean towel, then allow air to finish the job. A hairdryer on a cool setting works well on a patient horse.
• Apply a suitable antibacterial cream or barrier ointment as directed, and repeat daily until the skin is smooth, dry and hair is beginning to regrow.

Expect improvement within a week. If the scabs are spreading, the leg is swelling, or your horse is lame, stop and call your vet — prescription treatment or antibiotics may be needed, and there are other conditions that mimic mud fever.

Prevention Through Good Yard Management

Once you have dealt with an outbreak, the priority is stopping it happening again. Thoughtful turnout does more than any cream.

• Rotate paddocks and rest the wettest ones so they have a chance to recover.
• Move hay and water to higher, drier ground, and put down hardcore or bark chips in gateways.
• Bring horses in for a few hours each day during the worst weather, with dry legs and clean bedding.
• Check legs daily and towel them dry after exercise on wet ground rather than washing them.
• Avoid over-washing. Frequent shampooing strips the skin's oils and makes mud fever more likely, not less.
• Apply a barrier cream before turnout in persistent wet weather, and brush dried mud off gently once it has set rather than hosing it away.

Good doers, older horses and those with Cushing's disease often need a little extra vigilance, as their skin heals more slowly. With clean, dry legs, a daily feel and prompt treatment at the first scab, most cases resolve quickly and your horse stays comfortable right through the wettest months the British countryside can throw at you.