The trouble with mud fever is that by the time you notice it, it’s usually already well-established. Immediate action is required to try and stop it progressing to a very painful condition (which often includes swelling, pain, lameness, scabs, discharge and cracks and splits in the skin), with multiple infections (bacteria, fungi, yeasts, ringworm and mites), prolonged treatment and a long convalescence.
The first signs could be slight puffiness and reddening of the skin around the heel bulbs and back of the pastern. The area may look wet and greasy as serum begins to ooze, progressing to a white/green/yellow, smelly discharge of pus as more organism invade. As the discharges dry, they harden into thick crusts which protect the bacteria and fungi within the wounds. If they progress in severity, pain and heat increase, the whole lower limb swells and the horse may become very lame, fatigued and lose appetite.
Typically, wet conditions irritate the skin, and horses with white legs, pink skin, thick coats and feathered legs are at risk as the hair traps moisture and dirt against the skin. It is not mud but constant wetting and chilling of the skin that is the main cause — mud fever is more common where the legs are washed frequently, and very uncommon where the legs are almost never washed.
Greasy Heel is caused by the invasion of the bug Dermatophilus congolensis – which is a combination of a bacteria and a fungus. This bug also infects sheep (causing lumpy wool and strawberry footrot), cattle, cats, dogs, goats, humans, pigs and crocodiles. It often lives on the skin without causing any problems, but when the skin becomes soft and weakens, the spores germinate and invade, producing thread-like tentacles to penetrate the skin and spread in all directions. Secondary infections with bacteria like Staphylococcus, Streptococcus and Pseudomonas, yeasts, mites and fungi join in once Dermatophilus has taken hold. Leg mites, insect bites and ringworm can also get involved – irritating the skin and causing itchiness. Their diagnosis requires deep dermal skin scrapings from the edges of lesions
There are many treatments for mud fever – and as with anything that has a whole lot of treatments, it is often because nothing is a guaranteed success. Mud fever is difficult to treat and it can take weeks and weeks to heal completely - especially if it’s been ongoing and the skin has developed chronic changes. There are three rules when using ointments (i) all scabs must be removed (ii) the area must be completely dry to allow the ointment to penetrate (iii) apply generously.The affected area should be carefully clipped (with clippers or good, curved scissors). Wash with an antiseptic wash (see Table 1.) to remove as many scabs as possible.
According to Doug English, a veterinarian with over 45 years in equine practice, scabs protect the bugs and allow them to re-seed back into the skin. Reoccurrence will always happen because you can NEVER get rid of Dermatophilus congolensis – it likes moist skin and will continue to grow and invade. Dr English (http://turmericlife.com.au/) has developed a range of specialised formulae containing turmeric, the benefits of which have been confirmed repeatedly (ABC radio Dr Michael Moseley). 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, or a generous amount of baby oil, aqueous cream or udder cream covered loosely with gladwrap followed by a bandage (starting at ground level and taped to the hoof to prevent it riding up to the pastern) to keep it in place. Scabs will be very soft after 24-48 hours. Once the scabs are removed, gently rinse the skin and pat dry with clean, absorbent tissue. Rubbing it with a towel can be very painful and further abrade the skin. A hairdryer on ‘cool’ can be used. The scabs may form again quickly so initially the legs must be washed daily. However, washing a horse's legs repeatedly can remove the natural oils in the skin and may allow the condition to become established, so don’t continue longer than necessary.
Know when to get veterinary input. If you're having trouble removing the scabs, even after softening the scabs for days, or keeping the affected area clean, call your veterinarian. Your vet nay need to take samples of the affected area to determine which bacteria/fungi are involved. A correct diagnosis can determine the most effective treatment. For example, if the vet suspects autoimmune disease your horse may need corticosteroids; if feather mites are suspected, you need treatment to get rid of the mites and prevent the trauma from itching; if the bacteria and fungi have penetrated into the deeper layers and even completely through the skin (cellulitis), a course of antibiotics may be required. The use of antibiotic creams is unlikely to kill all the bacteria, especially those deeper in the tissues and oral or injectable antibiotics maybe be required for 4–6 weeks. However, antibiotics do not treat the fungal part of the infection and, there are real and increasing problems with bacterial resistance.
Once the infection has cleared up it is crucial to provide protection while the new skin and hair has formed. The first step is to remove the horse from wet and muddy conditions and apply liberal amounts of barrier creams and oils, such as pig oil, castor oil, goose grease, zinc cream, lanolin or petroleum jelly to protect the area while new skin and hair grows.
Hand-walking several times a day, is helpful initially. Once any lameness has been resolved, working on a dry surface which does not scratch the legs further will help the circulation and encourage healing. Roadwork is often best. Application of a barrier cream to DRY and CLEAN legs prior to exercise or turnout will help to prevent the skin coming into contact with the bacteria. There are numerous preparations available, but ones with a soothing emollient and oily base are best.
If you decide to leave the mud on overnight and brush off in the morning (more suited to heavy-feathered or unclipped legs), the mud is not trapped in the air and not in contact with the skin; in cold weather the legs will retain more heat so there is less chilling of body temperature from cold water; lots of the mud will drop off during the night, and grooming allows you to have a close look at the skin. On the other hand, the mud may hide small wounds and the grooming takes time! So you just need to work out what works best for you and your horse.
Despite the best efforts of scientists there is still no vaccine for mud fever. Controlling it is based on understanding the ‘perfect storm’ of factors responsible and knowing when to seek veterinary input.
EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart