Mud fever and Pastern Dermatitis

Lymphology and pastern dermatitis

Mud fever/pastern dermatitis/greasy heel.

Of course these have bacterial and fungal causes and wet, muddy conditions don’t help. But did you know that they are also often caused by lymphatic insufficiency?

When horses are stabled (or movement reduced such as when traveling for long periods) the lymphatic drainage in their distal limbs doesn’t function. You will probably know this familiarly as “stable fill” or “stocking up” – when the legs become puffy. This is actually pitting oedema, the longer term result of which is immuno-compromised skin. These horses who are stabled regularly develop higher risk of secondary infection… or mud fever/pastern dermatitis. They may also develop quite dry skin.

Arguably the most common form of exudative pastern dermatitis affecting all types of horses, mud fever is so called because it’s associated with wet, muddy turnout conditions which damage the skin and let bacteria in, causing infection. But the root cause of this can be lymphatic insufficiency from standing still for long periods of time.

Mud fever is commonly associated with but NOT limited to non-pigmented areas of pasterns. Skin scrape and targeted treatments to avoid it developing into cellulitis. Common bacterial causes are Streptococcus spp., dermatophilus congolensis, but may also be fungal.

The distal limbs are most affected because (unlike the rest of the body) they have no smooth muscle fibres to squeeze the lymph fluid back up the leg. It’s the flexion of the hoof and fetlock that does the job instead. To reduce movement is to reduce lymphatic drainage.

Over time you might see hyperkeratosis develop too, this again is a result of the lymphatic insufficiency but is easily managed with a simple healthcare emollient such as Diprobase or Cetraben.

So what can you do?

1. Increase movement. Turn the horse out 24/7 if you have the facilities to do so

2. Heal the legs. Flamazine, emollient, etc. Get the vet to swab to pinpoint whether it is bacterial or fungal (otherwise you could just be chucking money down the drain on the wrong products)

3. Encourage the horse to move around more in their stable when they’re not asleep by using enrichment

4. Learn about the products and therapies that are contraindicated (not to be used) for lymphatic problems. You may accidentally be making things worse because of how certain products are marketed

5. Ride that horse! Get them moving and be careful to do a good warm up and cool down. If they are non-ridden, groundwork can be helpful, particularly long lining and lunging. Make sure the horse is fit and sound enough for the work you are asking from them.

6. Check if your horse has pitting lymphoedema after stabling by using the Press & Stretch Tests, then check again after they have been turned out or exercised to see if the oedema has dissipated.

7. Mud protection – as much as we feel like “waterproofing” the legs will help, healthy skin requires the air to allow it to function properly. So choose breathable mud protection products in a cream form (eg NAF Mudguard). Fully water-/air-proofing the leg, especially if there are already wounds/sores present, runs a high risk of maceration. Macerated skin and wound beds will appear yellow, soft and may also have a bad odour.

Be aware that the terms “pastern dermatitis/mud fever/greasy heel” do not actually tell you what the problem is. Leg infections should be treated promptly and proactively because of the increased risk of cellulitis and secondary lymphoedema (especially in warmbloods and horses with CPL).

You can learn more about conditions affecting the legs here: https://chronicprogressivelymphoedema.com/pastern-dermatitis-and-other-lymphatic-diseases-of-the-legs/