Melting snow and heavy rain can only mean one thing to many equestrians: mud season. Every year during March, April, and May equestrians struggle with flooded paddocks, muddy horses, and all the equine dermatological conditions that come with it. One of the most aptly named and common of these skin issues is mud fever.
Mud fever, also known as pastern dermatitis, occurs when bacteria, fungi, and/or parasites enter through the topmost layer of the skin, leading to inflammation, pus, and even lameness. Continued exposure to mud and moisture causes abrasions that are prime opportunities for these little buggers to burrow past your horse’s natural defenses. On top of this, the waterlogged conditions in your paddock prevent your horse’s skin from drying out, creating the perfect breeding ground for bacteria. Recognizing the symptoms of mud fever is essential to prevention and successful treatment.
Warning: we hope you have a strong stomach!
Mud fever starts out innocently enough. You may find a few small patches of hair loss around your horse’s fetlock, particularly in the heel area, where mud tends to collect. These patches may start as a simple thinning of the coat, nearly unrecognizable as one of the symptoms of mud fever in horses. Who knows? This small bare patch could simply be due to a scrape after roughhousing with other horses.
It’s important to keep a close eye on these patches of hair loss and monitor their growth. Start treating the area immediately if they start to expand. Catching mud fever early is key to successful management.
Soon after the hair loss, scabs will begin to develop on the bare patches of skin. At first, they may appear dirt-like, dark brown, and crusty. However, after some time passes you’ll notice the scabs grow bigger. Over time the scabs will become bright red and follow the path of hair loss around your horse’s pastern and possibly even up the cannon bone. When removed, raw lesions will be exposed that are painful to the touch.
Depending on your horse’s specific case, the scabs may also appear as bumps developing under the horse’s skin and slowly scabbing over.
As the mud fever progresses, new symptoms emerge. Look for a clear serum-like substance oozing from underneath the lesions or various bald patches on your horse's leg. This serum is what gave mud fever the nickname “greasy heel,” as it’s slippery to the touch.
If you notice your horse’s heels developing a wet, greasy look on top of bare patches, act now. If you wait longer, the mud fever could begin to develop into a bacteria-harboring pus underneath the scabs.
Underneath the bright red scabs, white or yellow pus will start to develop. This pus can harbor a mud fever-causing bacteria, like Dermatophilus congolensis or Staphylococcal spp. This bacteria is known to live benignly on your horse’s skin in minimal to moderate quantities. However, given the right conditions, it breeds rapidly, spreading and causing an inflammatory response from your horse’s immune system.
It’s important to clean any pus carefully and thoroughly. If it is allowed to rest on uninfected areas of skin, the bacteria will quickly colonize the new areas and the mud fever will spread. The condition can be pretty painful at this point, so use caution while cleaning and be gentle!
Now, your horse’s immune system will be in hyper drive. Your horse’s pasterns have become a battlefield. The immune system is flooding the area with white blood cells in an attempt to overcome the infection. As the symptoms of mud fever progress, the legs may start to swell and become hot to the touch.
An easy way to find out if your horse’s legs are swollen is to look for signs of edema. For example, press a thumb with slight pressure into your horse’s skin. If a thumbprint is briefly left behind, then you’ve got edema. It’s time to call the vet! They may prescribe antibiotics to give your horse’s immune system a boost.
Mud fever can be a frightening and exasperating condition to deal with, particularly if you don’t recognize its symptoms and catch it too late. Keeping the area clean and protected by using a high-quality barrier cream is crucial to preventing its progress. While it’s always important to work with your vet, there is a management protocol you can start right away.
Cleaning the infected areas with povidone iodine solution or chlorhexidine kills the bacteria and stops the infection from spreading. However, don’t overbathe your horse’s legs! Bathing too
frequently keeps the skin wet for longer and benefits the infection more than the treatment. Focus on creating a clean environment that supports your horse’s skin health.
Many veterinarians and horse owners alike have had great success using Zarasyl to manage mud fever. In the case study pictured below, one horse showed a complete recovery in as little as 14 days. Learn more about Zarasyl and how it can be a significant part of your mud fever prevention and management plan here.