Getting Ready For Winter: Mud Fever & Cellulitis

Mud fever is a skin condition with multiple causes that usually affects the pastern region and is known as “pastern dermatitis”, “greasy heel” or “dew allergy”.

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This skin reaction can be seen in any horse breed but horses with feathers are particularly susceptible and can rapidly develop to an established skin infection if not treated properly.

Potential Causes Of Mud Fever

  • Trauma due to wounds, overreaching and incorrectly fitted boots
  • Ectoparasites such as mites
  • Poor environment conditions e.g. standing in deep mud or wet bedding
  • Chronic exposure to mild conditions e.g. excessive washing and scrubbing
  • Immune mediated diseases (e.g. contact allergic hypersensitivity to dew or different plants/soils)
  • Photosensitivity caused by altered liver function affecting only white skin, aggravated by sun light

Clinical Signs

These can vary depending on the trigger. Early lesions present with redness and loss of hair on the back of the pastern/above the heel. Chronic stages may show crusty scabs, ulceration, oozing or nodular masses.

Hindlimbs are mostly affected, and sometimes one hindlimb is worse than the other one. It can also cause itching and self-trauma, leading to abrasions.
If the horse has feathers around the fetlock, it is difficult for owners to observe these signs.

If left untreated, mud fever can cause cellulitis, chronic infection and inflammation of the soft tissues. This can in turn lead to a pitting oedema involving heat and pain, running from coronet to cannon bone, hocks or even higher. At this stage horses present with lameness and may not bear weight on the affected leg.

Diagnosing Mud Fever

This involves history of progression related by the owner, environmental conditions, examination of the affected skin and is usually easy to make if the classic clinical signs are present.

In some cases your vet will take a blood sample to rule out photosensitivity caused by liver disease. Scraping or biopsies may be taken to look for ectoparasites, bacterial or fungal involvement, immune mediated diseases, masses or other skin disorders.

Treating Mud Fever

Treatment is different depending on the clinical signs shown.

Horses must be kept on dry, clean bedding or turned out on dry fields or paddocks. If mites are involved, treatment against mites must be started.

Washing with dilute chlornexidine, rinsing and drying the skin and application of antibacterial cream often helps too. The scabs and crusts can be debrided if possible. The scabs will fall off after a few days of treatment and care must be taken not to cause further trauma.

Chronic wounds need to be cleaned and necrotic tissue must be removed. Clipping the feathers is helpful in order to clean the wounds, keep the skin dry, apply the cream and to monitor the healing process. However, for horses that have to be turned out, clipping the hair might worsen the condition as hair can be protective against sun light and external factors.

If cellulitis is present, systemic antibiotics and non-steroidal anti-inflammatory drugs must be started and in advanced stages corticosteroids might be necessary. Bandaging and bandage change a few times a day, cold compression and walking on dry ground will encourage swelling reduction. Appropriate treatment for individual cases should be discussed with your vet. Cellulitis can progress to lymphangitis, when the swelling goes from the coronet up into the groin, sometimes affecting the udder as well. In this stage horses present fever, high level lameness and lethargy.

Preventing Mud Fever

Mud fever is not easy to treat and recurrence is very common especially in the rainy season. That’s why prevention is very important:

  • Keep horses on dry and clean bedding
  • During rainy seasons, avoid turning horses out on muddy fields and use outdoor boots/bandaging if comfortable for your horse
  • Avoid recurrent wetting and washing if not needed
  • If washing, rinse and dry the legs thoroughly afterwards
  • Use barrier cream with caution prior to turn out as it could encourage bacterial infections
  • Sand schools can irritate the skin and washing to remove the sand might be excessive
  • Check your horses’ legs every day, remove mud and dirt using a soft brush

All this information being said, if not noticed early, mud fever can cause infection and discomfort, therefore it can be difficult to treat. If you are not sure about the skin disorder that your horse presents, do not hesitate to call your vet!

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