Oct 15 2011
Many horse owners assume that rain rot (dermatophilosis) is caused by a fungus.
However this is incorrect as dermatophilus congolensis shares characteristics with both fungus’s and bacterias. It is an actinomycetes, which behaves like both bacteria and fungi.
Many people believe that the organism is present in soil, however, this has not been proven. The organism is carried on the horse, who has it in his skin. A horse who has this organism in his skin may or may not be affected.
In horses the dermatophilus congolensis works by entering the follicle of the horses hair shaft. Once it’s in the horse’s hair shaft it can be seen in the form of a large hive. When these hives are removed from the skin horse owners can easily see several (literally dozens and dozens) of hairs embedded in each large lump. Because the dermatophilus congolensis damages the hair root removing these hives does not seem to bother or pain the horse in any way. Once the scabs/hives are removed owners can see that the skin under the hives is generally a pink color and oozing a yellow pus.
Dermatophilosis is a condition commonly referred to as rain rot, rain scald, and streptothricosis. Dermatophilosis that appears on the horses lower leg is often called dew poisoning. Although Dermatophilosis can be seen throughout the country it is most common in the southeastern portion of the United States where the weather condition is frequently wet, warm, and humid. It appears that the younger the horse the more likely it is to contract Dermatophilosis.
One of the factors that encourages the development of Dermatophilosis is that constant rain washes out the protective skin oils, softens the horse’s skin and allows the organism a chance to invade the skin.
Horse owners that have dealt with cases of Dermatophilosis say that their horses had scabs or hive like bumps on that measured approximately one fourth of an inch across, these hives are typically easy to peel or rub off. Although these lesions were most commonly seen covering the horses haunch area it is not uncommon to see the horse’s entire body affected by Dermatophilosis.
In the early stages, you’ll be able to feel small lumps on the horses’ skin or hair by running your hand over your horse’s coat.
Fortunately horses affected by Dermatophilosis do not seem to be in pain nor do they appear to be embarrassed by their condition. The only time the condition appears to be painful is if the area affected is a covered with a saddle. Owners who have a horse who has signs of Dermatophilosis on their spine should refrain from riding until the condition has cleared.
Video: Shows extreme rain rot (dermatophilosis)
Treating Rain Rot (dermatophilosis)
Typically, veterinarians recommend that the treatment of Dermatophilosis, when discovered early, is that the horse’s skin be dried and gently groomed to stimulate the body’s natural defense mechanism. However, if the condition is more advanced, it needs a more rigorous treatment. This is done by clipping away the hair surrounding the crusts and shampooing the skin with a medicated wash, such as Betadine or Chlorhexidine to remove the crusts. The uncovered sores will need an antibiotic ointment such as penicillin, amoxicillin and erythromycin. The application of the ointment will need to be repeated until the Dermatophilosis is clear up.
Contrary to the treatment I’ve just described is that you shouldn’t be using any ointments to treat Dermatophilosis because the ointments simply add moisture to the affected areas of skin. One old time method for treating Dermatophilosis is swabbing the affected are with used motor oil (for some reason fresh motor oil doesn’t have the same affect!). I must admit that this is a treatment I wouldn’t my use on my horse!!!.
When the Dermatophilosis has cleared up most owners like to bath their horses with antibacterial shampoos.
Dermatophilosis is contagious.
If you have a horse that has been affected by Dermatophilosis try to separate it from its pasture mates. Make sure that you keep its grooming supplies separated from those used on other horses. Don’t use leg wraps, saddle blankets, splint boots, and halters on any other horses. If you have to use equipment on other horses make sure you completely disinfect all the equipment before it touches their hide. Keeping equipment such as leg wraps and blankets dry will help prevent a second outbreak of Dermatophilosis.
Because the skin that has been affected with Dermatophilosis is hairless it is prone to sunburn. Rather than swab the bald patches with sunscreen which adds moisture to the skin, horse owners that keep their horses outside should use a fly sheet to protect their horse from UV rays. The blanket should be washed on a regular basis to kill the Dermatophilosis.
Finally, it’s usually hard to differentiate rain rot (Dermatophilosis) from other similar skin conditions, so if you are unsure, call your veterinarian.
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