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15 September 2014

MUD FEVER: GETTING IT RIGHT

Kieran O’Brien MA MVB PhD MRCVS

EqWest Equine Veterinary Clinic, Tavistock, Devon PL19 8QA

kob@eqwest.co.uk

This article appeared in the Arab Horse Society Yearbook 2004 and is reproduced with the permission of the AHS

Mud fever is very common in the Arabian breed, due at least in part to the high prevalence of white legs. Many owners and breeders struggle with this disease every winter. At an endurance ride held on the Quantock Hills in April a few years ago I was struck by the almost 100% prevalence of mud fever in the Arabian participants. A common complaint on my rounds is ‘I’ve tried everything and I can’t seem to get rid of it’.  The reasons for treatment failure are likely to be some or all of these

bulletAttempting to treat the disease without first removing all of the scabs overlying the lesions. No therapeutic agent is capable of penetrating scabby material
bulletUsing treatments which are essentially preventative (usually barrier creams of various sorts, often containing weak antiseptic agents) with minimal therapeutic effects instead of those that kill the causal bacteria (antibiotic creams and antibacterial skin washes)
bulletTreating only part of the affected area, or more commonly stopping treatment before the condition has completely resolved
bulletFailing to close clip the affected area. This will hugely improve the efficacy of treatment. Because horse clippers are too large and coarse to clip the hair of the heels adequately, fine (dog) clippers must be used

Removing the scabs

Anything which will soften the scabs will aid their removal. Scab removal without first softening is often difficult, and may be strongly resented by the horse. An ‘Animalintex’ poultice applied for 24 hours is useful. Alternatively a generous application of baby oil, ‘Dermisol’ (from vets) or ‘Sudocrem’ applied to the skin, covered with clingfilm and covered in turn with a stable bandage, will often have a marked softening effect after 1-3 days. It is essential that the clingfilm and bandage continue to floor level at the heels (reinforce with a few turns of duct tape) as otherwise these will ride up the pastern as it flexes leaving the lower skin crease untreated.

In spite of these softening treatments many bad cases will have to be sedated to allow complete removal.

Once the scabs have been softened the affected area should be washed with an antibacterial scrub such as Pevidine or Hibiscrub. The legs are wetted with warm water; the scrub is applied neat and worked in well to loosen any surface debris and scabs. The scrub is then left in place for 10 minutes (to allow a more effective bacterial kill), the legs are washed and thoroughly dried with a clean towel. This might be a good opportunity to close clip if it has not already been done.

What next ?

Removal of the scabs will expose several ‘raw’ zones, usually along the skin folds at the back of the pastern. These can now be treated by an antibiotic ointment obtained from your vet. Often cortisone is included in these ointments although there is some debate as to whether this is necessary. The old favourite, the green ‘Dermobion’ ointment is sadly no longer manufactured. Many vets are using effective alternatives, some of them ‘home made’. There are three rules about applying these ointments a) there must be no scabs present, b) the raw area must first be dried by gently dabbing with a tissue to improve adherence of the ointment c) they must be applied generously

It is best that affected horses are not ridden until healing is well advanced. They may however be walked on dry roads if desired

What if the leg is swollen?

Swelling of the leg, marked sensitivity to touch and the development of any lameness usually indicate that the infection has breached the full thickness of the skin. These cases will not respond to local treatment alone. They must have antibiotics by mouth or by injection, administered by your vet.

The day after

After the first treatment it is likely that some scabs will re-form overnight but these will be softer and easy to dislodge with a Hibiscrub or Pevidine wash. The raw areas as before are then dabbed with a tissue, and the antibiotic ointment re-applied. In bad cases I often recommend antiseptic washes twice daily for the first few days. Over the next few days the lesions will gradually heal but it is essential that treatment continues until the lesions have completely healed and the affected area is covered by healthy skin.

Preventing further attacks

Although the condition is traditionally associated with mud coating the legs, many out-wintered horses living in muddy fields happily go through the whole winter without developing any signs. The inevitable conclusion is that it is not mud but constant wetting of the skin that is the main cause. This theory is supported by the observation that mud fever if often rife in those yards where the legs are washed frequently, and virtually absent from yards where the legs are almost never washed. It is always better to leave the mud to dry naturally on the legs (leg wraps or bandages applied over the mud will ‘wick’ away the moisture) and then brush off the next day.

Waterproofing the lower limbs, the heels especially, before exercise or turn out is good practice. Thick creams such as zinc and castor oil cream, ‘Sudocrem’ or many of the barrier creams available from saddlers are effective. Udder cream although popular is a bit too thin for the job and hence is not very long lasting. In order to avoid getting greasy hands (and tack) every time you apply the barrier I recommend you use a cut-down paint brush to apply it.

Although it is traditional in winter to leave the lower legs unclipped as a preventive this is probably illusory. Indeed mud fever may be more common in horses with hairier legs, due in part to the longer time these take to dry out and to the difficulty in spotting early lesions.

If you must wash the legs then you must dry also. Sulphur powder or ‘Keratex Mud Shield’ powder sprinkled generously on the heels is very effective (even when sprinkled on wet legs) probably because these have a marked drying effect.

Spot the problem early

It is useful to get into the habit of running the fingers upwards against the direction of the hair at the back of the pastern every few days to detect the very small scabs indicating an early problem. If treated immediately these small lesions will respond very quickly.

If in spite of this advice you are still struggling to clear up this condition you need to seek veterinary advice. There are a number of other conditions that may mimic mud fever and it is important that these are considered in refractory cases. In addition there is a suspicion that long term treatment with certain substances can induce a local ‘allergic’ response, and you may inadvertently be making the problem worse.

The author welcomes comments on readers’ experiences with this condition, by email only to kob@eqwest.co.uk