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Medical Index
First Posted Sept 5, 2008
Dec 10, 2010

Ringworm and Horses

by Debora Johnson

See also my Lameness article

I have researched and written this article for my dear friend, Colleen. We are good buddies and use to trail ride together. She has now moved to Colorado so we talk on the phone and e-mail all the time. Distance cannot keep horse pals apart! She asked me about ringworm and said a horse at her barn had it and the horse had been isolated.

The following quote if from the Merck Vet Manuel.

"Trichophyton equinum and T mentagrophytes are the primary causes of ringworm in horses, although Microsporum gypseum, M canis, and T verrucosum have also been isolated. Clinical signs consist of one or more patches of alopecia and erythema, scaling, and crusting, which are present to varying degrees. Early lesions may resemble papular urticaria but progress with crusting and hair loss within a few days. Diagnosis is confirmed by culture. Differential diagnoses include dermatophilosis, pemphigus foliaceus, and bacterial folliculitis. Transmission is by direct contact or by grooming implements and tack. Most lesions are seen in the saddle and girth areas ("girth itch"). Treatment is generally topical because systemic therapy is expensive and of unproven efficacy. Whole-body rinses as described above for cattle may be recommended, and individual lesions treated with clotrimazole or miconazole preparations. Grooming implements and tack should be disinfected, and affected horses should be isolated."

Ringworm is not a worm but a fungal infection or fungal dermatitis (Dermatophytosis). In some ways it is similar to rain rot. An interesting fact is that a horse can actually carry ringworm without showing any signs, and infect other animals. Ringworm is NOT host (specific). In other words, ringworm on horses can be spread to other animals such as humans, dogs, cats, pigs, sheep, etc.

Identifying Ringworm

Ringworm sort of looks like a large hive on a horse, but with the other rim raised and the inner circle devoid of hair. It is most often circular, but can present in other ways. There can be scales and ooze present as well. Ringworm is really itchy. Your horse will rub and try to scratch it which can cause secondary bacterial infections. Dampness is ringworm's friend! It does not like sunlight and air. It is spread by spores--little devils that contaminate the stall, bedding, blankets, sheets, any tack, etc. They hang out and wait for their chance to invade. They may invade a cut or irritated skin; however, this is not always the case. The spores can live up to a year in the stall, paddock, tack, blankets, etc., nasty! Ringworm contamination can even be spread from a fence that an infected horse has rubbed. It is opportunistic, in that it usually begins in an area of skin that has been compromised in some way or invades a horse that may be immune system compromised. Horses 3 years of age and under are particularly prone to ringworm because they have not yet built up sufficient immunity. Also, horses who are older and may have nutritional, and other issues, are more at risk. However, any horse can get ringworm, if exposed to the spores, and the conditions are right.

What Do You Do?

  • Don't panic!
  • Call your vet to get a correct diagnosis.
  • Ask your vet for a med that can treat ringworm. Usually an anti-fungal. (Clotrimazole or miconazole preparations)
  • Ask your vet how to treat--what precautions to take, etc.
  • Decontaminate tack that you use on your horse. Lysol works and so does bleach. Ask your vet, first.
  • Isolate your horse from other companions to reduce the spread.
  • Protect yourself from becoming infected.
  • Clean out all exposed bedding from the stall.
  • Disinfect the stall, if at all possible.


  • Follow your vet's instructions, but the following are also some tips!
  • Put on throwaway plastic gloves to protect yourself. Ringworm is contagious! Do not reuse the gloves.
  • Clean the area and remove the hair around the ringworm. (Ringworm does not like air. It also feeds on hair, "keratin." Keratin is composed of protein.)
  • Shampoo your horse, all over, with an anti-fungal shampoo.
  • For cleaning preparations using an over-the-counter Betadine scrub or prescription Nolvasan works well. (Nolvasan is a staple in my first aid kit!)
  • Clotrimazole or miconazole preparations are prescriptions and are used for fungal infections.
  • Be vigilant. It takes time to get rid of fungal infections.

The prognosis, outcome, is excellent. Treatment and careful hygiene are key. generally ringworm is not an emergency, but it is really important to stop it in its tracks to prevent the spread. There you have it.

Medical Index