Rain scald (also known as ‘rain rot’) is a skin disease more commonly seen during the winter months, due to the frequent periods of rain or snow when the horses’ coat can remain wet for long periods of time.
The disease usually results from the bacterium Dermatophilus congolensis. During dry weather, the bacteria remains dormant, but can be spread from horse to horse by direct contact, contaminated tack and grooming equipment, or external parasites. Some horses can be chronically affected with the bacteria, but do not show any symptoms or develop the skin disease, these horses are called ‘carriers’.
For horses to develop this skin condition they must acquire the bacterium from a carrier, have breaks in their skin (ie from insect bites or minor wounds) and be exposed to moisture. Longer winter coats aid the development of the disease by protecting the bacteria from sunlight and maintaining the moisture required for the bacteria to reproduce and spread.
An affected horse will usually have numerous clumps of matter hair and the most commonly affected areas include the croup, loins, saddle area and neck. In severe cases this can extend to lower portions of the body and abdomen, following the path of water as it runs off the horses back. It is also possible for horses grazing in wet pasture to develop the disease on their lower legs, resulting in lameness, swelling of the fetlock and heavy scabbing of the skin, this is more commonly known as Mud Fever. Areas of white hair (ie socks, stockings, blaze, etc) are more sensitive to infection and might look red and inflamed.
In the early stages of the disease, rough, raised bumps often can be felt before they can be seen. These develop into painful, crusty scabs, which form under the hair clumps. Grooming is required to remove these scabs and hair clumps containing the bacteria and will uncover a moist, reddish ulcer in the skin. In some cases it may be necessary to soak these scabs with medicated shampoo in order to soften them and aid in removal, in severe cases this could be required over a period of several days. Once removed the area should be treated to kill any remaining bacteria and the scabs and hair clumps should be disposed of carefully so that they are not allowed to infect other horses.
During this recovery time it is necessary to remove any other factors which may add to the cause of the disease, such as wet coats, insect bites, etc and it may be necessary to stable your horse during periods of frequent rain. Treatment should continue per your veterinarian’s advice, using antiseptic shampoos, until signs of the disease have cleared up. In severe cases a course of antibiotics may also be required.
The bacteria can persist in the environment or on equipment for as long as four months, so in order to prevent re-occurrence it is essential that any tack or equipment used on the infected horse are cleaned and disinfected thoroughly. If a stable was used this should also be cleaned and disinfected as much as is practical. Remember, prevention is better than cure and good hygiene is the best safeguard against this disease.
Taken From Horse Connections