Equine Rain Rot
Overview: ‘Rain rot’ is a common diagnosis in Ohio based on our humid environment. ‘Rain rot’ is also known as Mud fever, scratches, or Dermatophilis and is caused by a bacterial infection. Dermatophilus congolensis, the bacterium found to cause this infection, is present on most horses and does not cause a problem until the outer barrier of the skin is compromised. The skin can be compromised from prolonged wetness, high humidity, high temperature, or attacks by biting insects.
Diagnosis: A diagnosis of ‘rain rot’ can usually be made by visualization. However, if more in-depth diagnostics are needed, a skin scrape or culture can be done. Clinical signs include paintbrush lesions (raised, matted tufts of hair) in horses with long, winter hair coats. Light-skinned areas are usually more severely affected. As the lesions get larger and join together, they will progress to a crust or scab formation that when removed will expose yellow-green pus between the necrotic and living skin layers. Common sites of ‘rain rot’ include neck, withers, back, croup and lower legs.
Treatment: Many cases can be treated by bathing the horse with an antimicrobial. Betadine or a betadine based shampoo is often the first line of treatment and is typically very effective. The scrub should be applied daily and allowed to sit for 10-15 minutes prior to being rinsed. The haircoat should be dried thoroughly. This is done until the infection is healed. If betadine is not effective, other topical antimicrobials are available through the practice. Advanced cases may also need oral or injectable antibiotics. Some severe or prolonged cases may require multiple or more aggressive treatments.
Prevention: The chances of ‘rain rot’ can be reduced through good hygiene. Groom your horse daily with clean brushes and clean your tack regularly. If you have a horse with suspected ‘rain rot,’ use separate grooming supplies and tack until the lesions are healed. Make sure you remove blankets in warm weather- sweating under a blanket creates a perfect environment for rain rot to start. Provide dry paddocks/ turn out, remove areas of standing water and mud. After bathing allow the horse to dry thoroughly, especially before applying a blanket or leg wrap.
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