Rain Rot

Posted by John Brand on

Although it hasn't been the wettest winter we've experienced, there has been some rain. With wet weather can come a plethoras of equine health conditions, one of which being rain rot. Some will tell you that this winter that they can feel small lumps on their horse’s skin under their coat. Could it be rain rot? How can you tell?

Dermatophilosis, otherwise known as rain rot or rain scald, is one of the most common skin infections seen in horses. It is caused by a bacterial infection and can often be mistaken for a fungal disease. The bacterial organism acts like both bacteria and fungus. It lives in the outer layer of the skin and causes large and small crusty scabs and matted tufts of hair.  There are usually dozens of tiny scabs that have hair attached and easily come out.  Sometimes after removing the scabs, the skin is pink with pus but becomes gray and dry as it heals. This condition is not life-threatening.

Rain rot usually appears first on the horse's back and rump, it can also be on the back of the fetlock, front of the cannon bone, tips of the horse's ears and around the eyes and muzzle. Typically, it is not painful to the horse. The scabs do not seem to cause an itchy feeling either. Removing the scabs may be painful to the horse.  Remove the scabs slowly and gently.  Many of the scabs may be brushed out when the coat is dry and sometimes wetting the area may be helpful in removing them. 

A horse can become infected by sharing equipment, blankets, leg wraps and brushes with other infected horses. The best way to prevent rain rot transmission between horses, is to use a disinfectant on any shared equipment after each use. Check with your veterinarian to see what disinfectant he/she recommends for use on your tack. 

 In order to thrive, the organism needs a warm, moist environment.  A secondary bacterial infection may occur. It is very important to treat rain rot immediately.  Any secondary infection may be quite resistant and more difficult to treat.

Rain rot can sometimes resolve without treatment.  Some horses can get rid of it as they shed out their winter hair coat. However, it is not advisable to let the condition continue, don’t wait to see if it will just go away.  Begin treatment as soon as you realize your horse has the condition, preventing it from getting any worse!

Dermatophilus congolensis, the bacterial culprit, grows better with a lack of oxygen. Since it doesn't like oxygen, you'll have to eliminate the heavy hair coat, and remove any scabs that hold the organism to the horse's skin.  It is not a good idea to use ointments, since they hold moisture and moisture needs to be removed for the condition to resolve. The best treatment is to wash the horse with veterinarian recommended antimicrobial and antibacterial shampoos and rinses, or even a Betadine scrub bath, as these medications help to kill the organism.

As always, we encourage you to keep your tack, grooming supplies and horses clean, and hopefully this helps avoid certain conditions.

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