What is Mud Fever in Horses
It is not really a fever, and has several different names: greasy heel, scratches, pastern dermatitis or dermatophilosis infection. It is actually a skin infection caused by Dermatophilus congolensis, a micro-organism that is best described as a cross between a bacteria and a fungus. The organism is a normal inhabitant of the skin of horses. For an infection to occur, two predisposing factors must be present: persistent moisture on the skin, damage to the skin.
It is usually found low on the legs of a horse, especially around the heels and back of the pasterns, from there it can spread up the leg. Un-pigmented skin (white socks) are more susceptible to mud fever because of the damaging effect of solar dermatitis. To read more about the negative effects of sun on your horse read our article ‘Effects of Sun on Equine Skin’. The often bare skin in the area under the back of the fetlock above the heel is quite pink and this is very susceptible especially if it had any reaction to sun during the summer months. Typically in winter the legs are often covered in wet mud, the moisture causes the skin to break down and open small cracks. It is this opening of the cause that allows the already present bug – Dermatophilus to enter through the skin which then reacts to form a scab. The constant presence of wet mud on top forms a seal which is the ideal environment for the bug to work away. Rain Scald is another name given to an infection by the same organism where the lesions are distributed over the body, neck and head, often on the back even if the horse has a cover on. The moisture from wet covers, or sweat, which is then kept covered is an ideal breeding ground for the bug.
What are the Symptoms of Equine Mud Fever
The infection is characterized by crust (scab) formation with or without swelling of the surrounding area. The crusts characteristically adhere to clumps of hair so when they are removed, the matted hairs come with them. Often the skin below is inflamed and oozes serum. There is usually a swelling of the pastern and it feels warm. The horse may or may not appear lame. Many horses move stiffly and reluctantly due to the discomfort of the sores in the skin. In severe cases where there has been no remedial action, the infection may spread up the leg causing swelling above the fetlock. At this stage a veterinarian should be called as the horse may need antibiotics and or corticosteroids.
How can Mud Fever be Prevented
Firstly a healthy horse that is on a well balanced diet, particularly with correct minerals and vitamin E supplementation, will be less susceptible.
Keep using a sun block ( UVA and UVB) to maintain the quality of the skin of white areas. Sun damaged skin will be much more vulnerable to cracking in wet conditions and therefore opening up to the infection of Dermatophilus.
In long wet winters prevention is not easy. Ideally the horse needs to be brought in from the paddock daily, the legs dried and cleaned and a check for any signs of skin deterioration. Washing off the mud, drying the legs thoroughly and using an antibacterial wash, particularly one containing chlorhexidine, will kill any bugs around the area. Covering the legs is not a good idea as the legs will still get wet and then you have created the ideal environment for the bug to develop. Generally, it is better not to clip the legs and leave on the feathers as these offer protection.
However once an infection occurs it may be necessary to clip way the hair so you can get to the scabs and resulting wounds in order treat the area.
Treating Equine Mud Fever
Early detection and action will always produce a better result. Scabs may not always be visible under the hair but you can feel them under your fingers so make sure you run your hands over the pasterns and particularly around the heels and under the fetlock joints, the lumpy scab will be obvious then. The scabs have to be removed and the easiest and kindest way to do this is to use a gentle shampoo, preferably a fungal cleansing shampoo. Work it in to a lather which will soften the scabs. Often a towel is all that is needed to remove them, sometimes you have to pick them off. It is really important to remove all scabs even if the hair is coming off with them.
Clean and dry the legs, look for signs of exudation. Use a chlorhexidine wash or cleanser as this will kill the Dermatophilous congonlensis, which lives under the scabs. The horse may be sensitive to the scab removal so go gently and reassure as if he becomes very uncomfortable he will only get more difficult to treat and then the infection can become serious. You never know when mud fever may occur so time should be spent in training the horse to accept having legs washed and dried regularly.
Once the skin is clean, then basically the sores are treated as wounds and then an antibiotic wound cream is the answer. Equifix-TTO Wound Cream is easy to apply , will not sting and assists rapid healing.
If the infection is casing excessive swelling, or it is above the fetlock, or the horse is clearly lame, then call the veterinarian as use of antibiotic and/or corticosteroids may be needed.
