Q: What are mud fever and rain scald? Are they the same thing?

Answered by Farryn Day 

Both mud fever and rain scald are caused by a bacteria, which is commonly found in the soil and on the skin. The bacteria only becomes a problem if it gains access to softened or damaged skin. As the bacteria enters softened or damaged skin, it causes inflammation of the skin and symptoms include reddening of the skin, itchiness and irritation, crusty skin and hair loss. A horse’s skin is extremely delicate and when it is waterlogged it becomes more susceptible to damage and infections. Even brushing past a spiky plant or working in a sand arena can cause micro-abrasions, which allow the bacteria to enter the skin.

‘Mud fever’ is the colloquial term for the condition described as ‘pastern dermatitis’ and it occurs, as the name suggests, around the pastern when horses are exposed to muddy or wet conditions for an extended period of time (see the image for this post). It can also occur when a horses legs are washed regularly and not allowed to dry before being put back into their stable. Excessive leg washing can remove the natural oils that act as a barrier, and this results in cracks which can allow the entry of bacteria. Certain bedding can also irritate the skin such as straw, as well as the chemical ammonia found in deep litter bedding systems. Boots and bandages (especially dirty ones!), which are incorrectly used can also damage the skins vital barrier. In extreme cases the pastern will become hot and inflamed, and the infection may travel up the limb, causing swelling of the leg right up to the knee or hock. The horse may ultimately go lame.

‘Rain scald’ is similar to mud fever except that it affects the horse over their back and quarters. It can be identified by the characteristic thin scabs often with hair attached to them, known as ‘paintbrush scabs’. Once the skin has been damaged, it can become vulnerable to infection with other bacteria and the lesions become infected and inflamed. Beware of using dirty saddle pads or numnahs as this can irritate and rub the skin, causing even more damage.

Treatment

• Keeping the area clean and dry is most important.
• Wash the affected area with an anti-bacterial and anti-fungal scrub or shampoo. Be sure to dry the area properly using a clean towel. Use a clean towel each time to prevent re-introducing the bacteria to the area.
• Your vet may prescribe an antibiotic ointment. Alternatively, if it’s not a severe case, Sudocrem can work very well. After you have washed and dried the area, apply the ointment liberally and try to keep the area as clean as possible. This will allow the skin’s natural barrier to heal.

Prevention

• During the rainy season, before turning your horse out, apply Sudocrem or Vaseline as a moisture barrier. It is important that the area is clean and dry before application or the cream will merely trap bacteria on the skin.
• Ensure that all numnahs or saddle pads, boots and bandages are clean and dry before each use.
• Should your horse wear over-reach boots permanently, check that they are not rubbing the sensitive skin of the pastern. While grooming, or tacking up, fold the over-reach boots up to allow the skin underneath to dry out.
• Clean your horse’s legs daily using a soft brush. Check for any cuts or scrapes and treat immediately.
• Should you hose your horse down after exercise, make sure that their legs are at least dry before going back to their stable.