Horse Health...

Resisting Rain Rot

While it's snowing in much of the country, winter often means lots of raining days, too - and an opportunity for your horse to get "rain rot."  Rain rot is one of the most common skin infections seen in horses. It is also referred to as "rain scald" or "streptothricosis". 

The skin usually has a cut or scrape for the organism to be able to enter the system though the skin.  A horse can become infected by shared saddle blankets, leg wraps and brushes with other infected horses  In addition, any equipment that may rub (i.e. polo wraps or boots) can irritate the infected skin.

The organism dermatophilus congolensis causes rain rot. It is not a fungus, but anactinomycetes that behaves like both bacteria and fungi. Most people believe that the organism is present in soil, although this has not been proven. The organism is carried on the horse in his skin; however a horse that has this organism in his skin may or may not be affected.  

Rain rot can appear as large crust-like scabs or small 1/4 inch matted tufts of hair usually on the horse's back and rump, along with the back of the fetlock and front of the cannon bone. It may also appear on the tips of the horse's ears and around the eyes and muzzle. When rain rot appears on the lower limbs (behind the fetlock), it is most commonly referred to as "dew poisoning". In the early stages, you will be able to feel small lumps on the horses' skin or hair by running your hand over your horse's coat. There is usually dozens of tiny scabs that have embedded hair and can be easily scraped off. Underneath the scabs, the skin is usually (but not always) pink with puss when the scabs are first removed, then it becomes gray and dry as it heals.

Rain rot is not life threatening.  In fact, if left untreated some horses will naturally get rid of the organism as they shed out their winter hair coat.  But this is not recommended.  It is best to treat start treating the disease as soon as possible, especially to keep it from spreading. It can also develop a secondary bacterial infection, such as staphylococcus (staph) or streptococcus (strep), making it more resistant and difficult to treat.  

The best treatment is to wash the horse once a day for a week with antimicrobial and antibacterial shampoos and rinses like Betadine, help to kill the dermatophilus congolensis organism.  If your horse has a heavy coat, clip him first.  Keep the horse in a dry, clean area that is very well ventilated. Separate the horses with rain rot from those without it.   When treating this condition, you must also keep all equipment used on the horse disinfected to keep from him becoming reinfected.  You can use a solution of 2 tablespoons or bleach to 1 gallon of water to wash any of the horse's blankets, saddle pads, leg wraps, etc.

In severe cases, your veterinarian may recommend a course of penicillin or other antibiotic to help get rid of the organism.  Contact your veterinarian if you do not see improvement of the condition.

Originally published by Classic Equine Equipment December 2015 Newsletter