With the recent large amounts of rain here in the Mid-South, several moisture-loving bacterial and fungal ailments are making themselves known throughout the equine population: thrush, white line disease, and rain rot to name a few. Combined with the already hot and humid conditions summer brings, the extended rainfall creates the perfect conditions for opportunistic organisms to thrive.
Rain rot, also known as rain scald, or dermatophilosis, is a skin condition in horses caused by the bacterium, dermatophilus congolensis. Acting as more of a fungus than bacteria, this microorganism creates a skin infection in your equine, causing painful scabs, lesions, and bald spots over your horse’s face, neck, chest, and topline. Dermatophilus congolensis is a common bacterium found on the skin of numerous mammals under normal conditions. However, it may become irritated when the equine’s skin remains wet for an extended period of time or goes through wet-dry-wet periods under rainy weather conditions. Consistently damp skin cannot maintain the natural barrier it normally provides under dry conditions.
Rain rot is not something horse owners or caregivers need to worry about if the horse is simply left to air dry after a bath or has been rained on. The risk for this condition is associated with prolonged saturation of the skin combined with a route for the dermatophilus congolensis bacteria to enter the body. This can be via an open wound, scratch, or insect bite. Once the bacteria has entered the horse’s system, infection can set up.
If you suspect your horse has rain rot, contact your veterinarian if warranted, and give your horse a bath with an antimicrobial soap, such as those containing chlorhexidine, povidone-iodine, or benzoyl peroxide, as a good place to start. Lather up, shampoo, let your horse soak for about 10 minutes, then rinse. Remember to wear gloves; rain rot is zoonotic, meaning it can be transmitted from animals to humans. Gently remove loose scabs, as this will expose the infected skin, therefore, allowing direct exposure to treatment. Address any open insect bites, minor abrasions, or lacerations with an antibacterial spray or ointment. Healing the bacteria’s points of entry will prevent further complications. Povidone-iodine ointment should also be applied to adherent scabs in order to soften them for future removal. Veterinarian prescribed antibiotics may be required in equines with severe rain rot who are not getting better with topical treatments.
It is important to note horses affected by rain rot should be isolated and any equipment (halters, lead ropes, feed buckets, water troughs, etc.) that has come in contact with them should be thoroughly disinfected. Any scabs or crusts removed from the equine’s body should be disposed of properly and not just thrown on the floor of the stall, barn, or in the pasture in order to prevent a source of reinfection. Prevention tactics include keeping your horse dry by providing shelter to get out of the rain if the horse chooses and removing any wet summer fly or stable sheets, thus allowing the horse to dry quickly after a rain. Of course, wash your hands thoroughly after handling or treating an infected horse.