Rain rot, technically known as dermatophilosis, is often mistakenly believed to be caused by a fungus. However, this condition is actually caused by the bacteria, Dermatophilus congolensis. Interestingly enough, the same bacteria are also responsible for heel dermatitis (also known as Scratches or Mud Fever).
According to Merck Veterinary Manual, this bacteria lives dormant within the horse’s skin until the skin becomes compromised in some way. This can happen when there’s prolonged wetness, high humidity, high temperatures, or even attacks from biting insects. However, rain rot is most often seen in horses with compromised immune systems (from improper nutrition, old age, or Cushing’s disease). In some cases, it may also be spread from horse to horse by biting insects, shared saddle pads, or shared grooming supplies.
Rain rot is fairly easy to identify because of the peeling skin lesions which scab over, often leaving bald spots once they come off. But a veterinarian can confirm the diagnosis by examining a skin scraping under the microscope and/or having it cultured.
Treating Rain Rot
Rain rot may clear up on its own, but you can hasten your horse’s recovery by using an iodine-based, medicated, or herbal shampoo and/or topical treatment. In the early stages, a tea tree oil-based shampoo may help, but according to Horse Journal, Absorbine Medicated Shampoo and Spray is a better option for moderate cases. Horse Journal also recommends the tea tree oil-based sheath cleaner, Excalibur by Farnam for use on areas with thick scabbing. Vetricyn spray is another topical option.
Preventing Rain Rot
Since rain rot is associated with a compromised immune system, supporting your horse with nutrition is one of the best ways to prevent the condition. Trace minerals, especially copper and sulfur should not be neglected. (Feeding MSM is one way to add supplementary sulfur.)
Helpful herbs to feed include:
- Chickweed;
- Nettle;
- Red Clover;
- Licorice;
- Echinacea;
- Fenugreek, and
- Dandelion.
Since biting flies can also aid in the initial infection as well as the spread of rain rot, using fly sheets and mesh leg covering may be helpful, especially for older or compromised horses. Additionally, if any of your horses do experience rain rot, it’s important to disinfect grooming supplies and not share tack between horses.
Have you ever had a horse with rain rot? Feel free to share how you treated the condition in the comments!
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