Uh-oh… ‘tis the season to get mud-fever!

Mud fever – or “Pastern dermatitis” – was traditionally been considered to be caused by Dermatophilus congolensis, a gram-positive, facultative anaerobic actinomycete… now you have the knowledge to be successful in the world’s most obscure pub quiz, let’s talk about mud fever!

What has mud got to do with mud fever?

Mud fever may be referred to as ‘pastern dermatitis’. Bacteria can survive in the upper layers of the skin. If the lower limbs and pastern region are persistently wet, this may adversely affect the integrity of the skin’s natural defences, allowing this nasty critter to infect your horse’s skin.

Spreading through the epidermis, the bacteria are capable of causing an acute inflammatory reaction. The immune system can tackle such an inflammatory reaction in 2-3 weeks. However, if the skin is persistently wet and damaged, the affected skin may form a scab, and the wet conditions encourage release of more and more bacteria, perpetuating the infection.

Although D. congolensis is an important cause here in the UK, some more recent research is suggesting that a wide range of different bacteria can be involved. As a result, Mud Fever (or Pastern Dermatitis) is now considered to be more a reaction pattern of the skin to bacterial invasion, rather than a being 100% limited to a specific bug.

What allows infection to take hold?

Conditions that make a condition more likely to take effect are referred to as ‘risk factors’. Some of these include:

Environmental conditions

Wet, muddy conditions persistently can cause the damage to the pasterns needed to allow bacteria – especially D. congolensis – to multiply.

Parasites

Fungi can cause damage to the skin; any condition compromising the integrity of the epidermis in the pastern region will predispose to this infection. Chorioptic mange mites may be seen more in our hairy-legged fellows, however, these tiny mites can cause irritation and are thought to be associated with the development of pastern dermatitis.

Auto-immune diseases

Particularly ‘leucocytoclastic vasculitis’; this auto-immune condition occurs when the immune system recognises part of the horse’s body as a foreign threat; in this case, the unpigmented lower limb. It’s rare, but in cases that don’t resolve rapidly, it is worth looking into.

What does mud fever look like?

Areas that have been continually subject to wet conditions or damage will present most acutely with mud fever; that is to say, the areas that look the worst are the areas where the bacteria have been able to spread the most. Some common signs include:

  1. Scabs with matted hair. The skin under this will be moist and ulcerated; they are sometimes said to look like “paint brushes” as the hairs stick to the scabs
  2. Discharge; this may be thick and white, cream-coloured or green
  3. Cracks in the skin; cracked heels and horizontal ‘fissures’ may be evident in severe areas
  4. Baldness; the hair may fall off in the affected areas
  5. Heat, pain and swelling in badly affected areas; if very severe, the horse may actually be lame

Is there a cure for mud fever?

Prevention is the best cure! Treatment is based upon cleaning the area and helping the healing of the skin. In some cases, anti-inflammatories and antibiotics may be indicated.

  1. Clean the affected area! This involves removing the scabs, as they are defending the organisms underneath. This can be painful, and some may require soaking/poulticing, so always consult your vet before embarking on peeling them all off, for your safety and the horse’s welfare. The area can then be cleaned with a medicated scrub, such as chlorhexidine or povidone iodine.
  2. Dry the area. Remove the horse from the environment which is a source of the issue; for example, if they are kept out, it is advisable to stable them to keep them out of the damaging wet/mud. Equally, if they are in a very wet bed, ensure the stable is kept clean and dry.
  3. Protection. Creams and ointments may be advertised, however, it may be preferable to keep the skin dry and clean, free from any further sources of moisture. Bandaging can be useful in aiding cleanliness.
  4. Medication. In very severe cases, your vet may prescribe an antibiotic to help your horse’s immune system in fighting the infection. Anti-inflammatories can also aid in acute cases, especially if your horse is suffering from swelling, pain or lameness as a result of the inflammation from the infection.

I know my horse often develops mud fever, how can I save us both the hassle this year?

Ensuring your horse is in an environment where the bacteria won’t be able to take hold, i.e. keeping the pastern skin as healthy as possible, is the way to keep a healthy, happy horse -whatever the weather!

Consider your management regimes; if your four-legged friend is turned out, is his paddock getting poached? Does he tend to stand my a churned-up gate? Try keeping the paddocks in a rotation system to prevent them getting too muddy, and leaving his hay in dry areas to encourage him away from the temptations of the marshes of the gate. Fencing off particularly bog-ridden areas can also be an option. Keeping bedding dry and clean is also essential! When turning out, protective emollients and boots can provide protection against wetness.

Everyday routines may be irritant to already inflamed legs, without us even realising. These include sand arenas and abrasive dandy brushes being used with too much force. Also, while we want to keep legs clean, we must establish a balance between cleanliness and over-washing!

Vigilance in spotting the early signs of mud fever is pivotal in maintaining healthy limbs throughout winter. Knowing what your horse normally looks like, together with early spotting of any hair loss, strange hair patterns, swelling and scabbing are vital.

All of us here at VetHelpDirect wish you luck in maintaining your ponies’ perfect pasterns!

“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” ― Mahatma Gandhi