Mud rash in horses

Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School

What is mud rash?

Mud rash is one of the common names for a range of skin reactions in horses, which can result from a collection of factors and diseases that cause irritation, damage and infection of the skin on the lower limbs of horses. It is also known as mud fever, scratches, greasy heel and cracked heel. As its names suggest, mud rash is generally seen in horses when ground conditions at pasture are wet and muddy. The wet conditions cause the skin to soften and the mud can then rub against the skin and cause abrasions to the skin surface, which is why mud rash is mostly seen in the autumn and winter months when wet weather and muddy conditions are more likely. There is also some evidence that certain soil types appear to predispose horses to mud rash.

 

Skin is the horse’s largest organ and it acts to protect the body from the outside world, acting as a frontline barrier where it contains elements that help prevent microbial colonisation. However, when the skin is exposed to wet conditions for long periods of time the outer layer begins to absorb water causing swelling and softening of the skin. This begins to weaken the protective barrier of the skin and more so if the legs are repeatedly dried and then re-exposed to the wet conditions. This then permits microorganisms to penetrate the weakened skin. Microbes that are dormant on the skin or present in the soil are able to invade the damaged skin causing inflammation and infection. This painful infection by certain microorganisms, such as Staphylococcus aureus and Dermatophilus congolensis, results in the secretion of a greasy discharge, which is why this condition is often referred to as greasy heel. Other factors that can cause mud rash are allergies, irritants, fungal infections and chorioptic mange mites.

 

What are the signs of mud fever?

It is often the case that the first signs of mud fever are splits along the horse’s heels, which if left untreated lead to crusty scabs beginning to form as a result of the greasy discharge that is excreted as it accumulates on the leg hair. This then causes the hair to mat, creating what looks and feels like a hard scab. Again, if this is unnoticed and untreated then the condition will worsen and begin to spread further and deeper into the skin. In severe infections there can be a cluster of scabs that develop and the area can become very swollen. In such cases, the horse may also be lame as a result.

 

How can mud fever be treated?

If you suspect that your horse has mud rash then it is advisable to consult your veterinarian. The main aim of treatment is to keep the skin clean and dry. It may be necessary to keep the horse stabled for some time to remove exposure to the wet and mud.

 

In some cases it is advisable to clip the surrounding hair to help improve air circulation and thus reduce the moisture content. Clipping the hair also enables topical treatments to be applied

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