Under normal circumstances the horse’s skin and protective coat form effective barriers against the winter elements. However, in very wet and muddy conditions this natural barrier can often be compromised and infectious agents (pathogens) gain entry and cause infection. This can result in the relatively common bacterial infections: rain scald, mud fever and hunting dermatitis.
Winter Rain Scald ( Dermatophilosis)
Winter rain scald is an inflammatory skin disease caused by the invasion of the bacterium Dermatophilus. As the name suggests, the condition may arise when the horse is subject to prolonged rainfall and the resultant wetting of the coat. Therefore this problem most frequently affects grass kept horses during the winter months.
There are a number of factors which may pre-dispose the horse to this condition, such as:
- Conditions of persistent driving rain
- Inadequate access to shelter (either man-made or natural)
- Horses with fine coats and thin skins such as Thoroughbreds, Arabs and some sports horses are at increased risk.
Once the disease is established the signs of winter rain scald make diagnosis quite straightforward, but unfortunately the early signs in grass kept horses can easily missed. This is especially so during the darker winter months, when day length is so short.
If affected, the horse’s coat will have a matted and crusted appearance; small bumps can be felt under the skin. There may be a serous (clear) discharge coming from the affected area and the hair will be tufted. Once the scabs fall off, the skin underneath will be sore and may have some purulent (pus filled) discharge). Affected areas will have severe hair loss (alopecia) which will follow the areas of the horse most commonly soaked by rainwater. Indeed, rugged horses may be affected, if leaking rugs are not removed and replaced with dry ones.
In very severe cases the condition can cause un-thriftiness, weight loss, fever and can be debilitating; it should be considered to be welfare issue. Veterinary consultation should be sought for the treatment of rain scald. Prevention can be achieved through the use of correctly fitting waterproof rugs (which should be changed if they become soaked through), adequate shelter and by supply of a nutritionally balanced diet to ensure general well-being and successful skin and hair regeneration.
Equine Pastern Dermatitis (EPD or Mud Fever)
Equine Pastern Dermatitis (EPD) is more commonly referred to as mud fever, mud rash, greasy or cracked heels. The bacterium involved is usually D. congolesis, which also causes both rain scald and hunting dermatitis.
The condition has typical clinical signs of: Serious discharge, crusted areas and hair loss first appearing in the bulb of the heels and then spreading into the back of the pastern. Often the scabbed area will become secondarily infected with another bacterium and the infection will worsen. The infection can progress to limb inflammation (with associated swelling, heat & pain) and lameness will ensue.
The cause of mud fever can be multi-factorial (i.e. have a range of different causes) but is most commonly due to prolonged wetting of the coat and exposure to deep muddy conditions. The disorder is also more common in horses with copious feather, as the early signs of infection can easily be missed.
Acute and severe cases of mud fever MUST be seen by the veterinarian. This includes; any lameness, limb swelling, marked discharge or odour. Mild cases can be managed successfully by the owner and will generally require the horse to be stabled until the skin is healed, or at the very least be kept in a dry, mud-free environment. Treatment will involve keeping the limbs clean and dry, cleansing the legs with mild antiseptic shampoo and the application of topical antiseptic treatment. It may be necessary to clip the legs, but this should be done with extreme care.
Always seek veterinary advice when deciding upon the correct choice of treatment. If veterinary assistance is required, it is likely that systemic antibiotics will be given and a supportive topical (skin) treatment.
Mud fever prevention is always preferable to treatment and this can be achieved through good husbandry. The horse should have access to shelter and the ability to avoid deep mud, keep the limbs clean and dry whenever possible and carefully check the lower limbs during the winter, paying particular attention to heavily feathered limbs.
Hunting dermatitis (Ventral Trunk Mud Fever)
Hunt horses or those working/ competing in wet and muddy conditions through the winter months, such as team-chasers, point to pointers and National Hunt racehorses, are most commonly affected by ventral trunk mud fever.
This bacterial skin condition affects the ventral abdomen (belly) and inside of fore and hind legs. Clinical signs are likely to appear quickly (i.e. the evening of a hunting day) and veterinary consultation may be needed if the horse is very sore. If a mild case, careful owner management can be successful. Mild antiseptic shampoo in warm water should be used to remove mud, drying the area in a hygienic manner through the use of clean towels and ensure that the bedding is clean.
With a mild case, the horse is likely to be off work for a number of days and hard (concentrate) feed should be reduced accordingly. The horse should be effectively sick nursed.
Veterinary treatment must be sought for severe cases or mild cases which fail to respond to owner management or quickly resolve. Veterinary treatment will involve oral antibiotic therapy.
As with all other Dermatophilosis conditions, all treatments should be continued until all of the affected skin is healed, with close attention to husbandry and hygiene maintained throughout to minimise the risk of re-infection and further complication.
Sudden Acute Lameness
In wet and muddy conditions small cuts and wounds on the lower limbs can easily be missed and pathogens can gain entry, resulting in minor infections. Any incidence of unexplained sudden lameness should initially be treated through careful inspection of the limbs and foot. Veterinary consultation is recommended and is likely to involve trimming away surrounding hair before careful cleansing of the affected area with warm antiseptic solution and cotton wool swabs. If the wound is away from joint, poulticing may be used to draw out any deep seated infection. If a poultice is applied too close to a joint there is risk of drawing out the lubricating fluid from around the joint; which can have serious consequences.
The horse will most probably require stabling during the treatment period. If the horse is not vaccinated against tetanus, the veterinarian will give an anti-tetanus injection, as the pathogen causing tetanus ( Clostidium tetani) is a soil-borne organism and may have gained entry into the body via the wound. Ideally ALL horses should be routinely vaccinated against tetanus.
If the horse has unexplained sudden lameness and a wound cannot be found; the injury may be a puncture wound. This type of wound can be quite common if hedges surrounding the field have thorns. The affected area will be quite painful, inflamed and hot; all of which will worsen if untreated. Veterinarian assistance should be sought as these infections can become quite nasty. Oral antibiotics may be given if the Vet is unable to remove the thorn and the area should be poulticed.
Finally, the condition pus in the foot may occur during the muddy winter months when the risk of bacterial infection tracking into any small puncture wound is heightened. Pus in the foot is well recognised as a common form of lameness in the horse and is caused by a bacterial infection of the vascular layer of the solar corium (internal to hoof wall), via a penetrating foreign object.
The condition may be sudden in onset or gradual and is identified by the following clinical signs:
- Pain- either lameness or on use of hoof testers
- Inflammation – detected as heat in the foot
If not treated, lameness will progressively worsen and may even result in a systemic infection (i.e. one which affects the whole of the body and is not isolated to one localised area). Treatment requires the application of a warm poultice to draw out the infection. This is now most commonly achieved through the use of an Animalintex™ poultice but can also be done using the more laborious technique of tubbing. Tubbing requires the animal to stand with the affected foot submerged in a bucket of saline solution for approximately 10 minutes twice daily (a technique which is often not easy achieved).
Many of these conditions can be avoided with the application of good husbandry and a watchful eye. Equally, if they are encountered careful management can help to resolve the problem quickly. However, conditions which are serious, do not respond to management/ treatment or quickly improve should always be seen by the Vet; as should all problems for which the owner is uncertain.
Alison Pyatt BSc (Hons) PgD, PGCE, BHS IT, is a Lecturer in Animal Science at Harper Adams University College specialising in large animal health and disease. She also owns and runs a small livery and training yard, Glebe Farm Equestrian, which based in South Shropshire. Glebe Farm Equestrian specialise in breaking and schooling and the retraining of racehorses.