Mud fever is a common skin disease in horses, especially prevalent in wet conditions. The proper name is pastern dermatitis, and it is caused by an infectious agent called Dermatophilus congolenis.
When the skin at the bottom of the legs is compromised, for example a wound in prolonged saturation (in wet weather), the infection can take hold, causing an acute inflammatory reaction with active infection.
This can be further complicated in horses suffering with infestations of tiny mites.
Generally, these affect heavily feathered horses and this can compromise the skin and allow the dermatophilus to spread. Older horses and ponies, especially ones with cushings, a disease affecting the immune system, may be more prone too.
The signs of mud fever are crusty scabs, moist lesions under the scabs and sometimes white/green discharge between the skin and the scab. As the disease progresses, deep fissures form under the skin with hair loss, leaving the skin looking raw and inflamed. This can progress to swelling of the limbs and lameness.
To treat this common, but nasty infection, it is imperative to keep the skin clean and dry. This often means that the horse needs to be stabled for some time.
The aim is to get the bug, which sits under the scabs, therefore all the scabs need to be lifted, which can be a painful process and require sedation to be done properly. Usually the hair needs to be clipped and the scabs soaked off. Then the area needs to be washed with hibiscrub/chorhexadine and warm water. This needs to be thoroughly washed off and dried, which is the most important part.
Once dry, there are numerous creams which can be used. We make up one at the clinic which contains antibiotics and anti-inflammatries. The horse may require injectable or oral anti-biotics and anti-inflammatries too. This can take some time to resolve.
Preventing mud fever can be difficult in this country as we have such wet weather, but if you have a very susceptible horse, it may be beneficial to stable it at night, brush dried mud off rather than wash it, and potentially use barrier creams.
There are some nutritional supplements which may help as well.
The most important thing is to be vigilant and keep a close eye on your horses’ legs for any signs of mud fever because prompt treatment is best.
By SAMANTHA CASTLE, Vet