I have recently come into contact with a ring worm infection in my young colt. Ringworm has nothing to do with worms, and sometimes it has nothing to do with rings. Ringworm is actually a type of fungal infection of the skin.
Ringworm in horses is often caused by the Microsporum and Trichophyton species of the fungus. These species can also infect humans, cattle, cats, dogs, and other animal species, so it is highly recommended to wash your hands and change your clothes after coming into contact with an infected animal.
Ringworm in horses can start out as a raised plaque of hair anywhere on the animal. At first, I had thought that they were bug bites. There were about 5-10 raised bumps on my horses back that were about centimeter in diameter. After one week the hair had started to fall off leaving little hairless circles. Ringworm can also be very itchy. In some spots I could see that my horse had itched, so instead of a hairless patch, my horse had a bloody welt in some places.
Ringworm spores can exist in the outside environment, but it is often transmitted through fomites like contaminated tack, blankets, or barns in general. In addition, it can also be transmitted from horse to horse, or from animal to animal. As with most illnesses, young and old animals are more susceptible to infection which is why my colt (who is not yet a year old) got infected.
A veterinarian will diagnose ringworm through just looking at the lesion. Sometimes the veterinarian or technician will also take a skin scraping of the lesion to examine under the microscope. Ring worm spores can be easily seen under a microscope if the spore burden is high. If not, a sample from the skin scraping can also be cultured and grown in an incubator for more definitive results.
There are two main treatments for ringworm in horses. One is a topical antifungal treatment that is applied a couple times directly on the cleaned skin of a lesion. The other treatment, used in more severe cases, is an oral treatment of griseofulvin which is generally prescribed for two weeks. Sometimes a combination of treatment is recommended.
In all cases, it is recommended to call the vet over to take a look at the infection and they will decide on the appropriate treatment and will confirm if it is indeed ringworm.
Overall, ringworm can cause an itchy, contagious, mess. But, quick observation of the infection and quick action for treatment will yield the best results for your horse.