Disclaimer: The following is only general information. If you believe that your horse has a problem please call your veterinarian as soon as possible.
This is a highly contagious disease, which can quickly infect the other horses on your property or your boarding stables, as well as you and your other pets. It is not caused by a worm, it’s actually caused by ‘skin loving’ fungi (dermatophyte) and the two fungi species that cause Ringworm in horses are Microsporum and Trichophyton.
Younger horses are more likely to be affected than older ones, although very old and debilitated animals are also susceptible.
Infection produces an immunity which is quite long-lasting.
Ringworm spores in chains in a horse’s hair as seen under a microscope.
Lesions begin as circular areas of raised hair about 1 – 3cm in diameter. The hair becomes brittle and falls out about 10 days after infection. You can also pluck the hair out leaving a moist, circular, hairless lesion, which may be dotted with spots of blood.
The most common sites of infection are the head, girth and shoulders, however if left untreated or spread by grooming gear they can become a more generalized, extensive infection.
Sometimes the lesions are sore and itchy, while in other cases they don't appear to cause discomfort. Also the lesions can, at times, be confused with other skin conditions such as Rainscald or Folliculitis.
Your veterinarian may take a skin scraping of skin cells, debris and hair to confirm the diagnosis.
Ringworm is highly contagious, therefore it can be spread by:
Contaminated equipment – girths, boots, rugs and grooming gear
Direct contact with an infected horse (commonly a new horse introduces the fungi to a property)
Indirect contact where an infected horse rubs against a post or tree and leaves behind fungi in the loose hair, another horse can then come and rub on the same spot (the fungi can remain in the environment for a long time)
Flies, mosquitoes and other biting insects can also spread Ringworm
Horses with Ringworm are considered contagious for at least 3 weeks from the time of infection.
Isolate the infected horse from all non-infected horses
Thoroughly wash the horse daily with an iodine scrub or other anti-fungal wash (follow your vet’s advice with regards medications, dilutions and applications)
Gently lift the scabs or crust while you are washing (you can not kill the fungi if you leave the scabs on)
After your horse has dried off, dab each of the hairless lesions with a tincture of iodine or anti-fungal ointment
Collect scabs and loose hair, bag and burn it
Disinfect by wiping down your horse tack and soaking your grooming gear with 0.3% chlorine based solution (Halamid is one but there are several others – ask your veterinarian)
If hairless areas are increasing in size and number, contact your veterinarian immediately. Your vet may wish to grow (culture) the fungi in a laboratory to determine the type of fungi involved – this may help to determine the best treatment. Unfortunately, fungi are harder to grow than bacteria, and the process can take several weeks to get a result. In the meantime your vet may just choose to use alternative treatments.
For generalised infections, or where more than one horse is involved, your vet may prescribe an anti-fungal powder to put in your horse's feed. Unfortunately, this treatment can take up to 6 weeks to be effective so it is usually used in conjunction with a topical anti-fungal ointment.
As with most contagious diseases, a horse can have a disease for some time before any clinical signs appear. With Ringworm, the fungi can remain on the skin for up to three weeks before lesions appear, so one of the most important preventative measures for Ringworm as well as other diseases is to quarantine all new horses for two to three weeks.
While all new horses are in isolation, you should be monitoring their health by taking their temperature every day as well as looking for skin problems and discharge from their nose and eyes. If you see any clinical signs of ill health contact your vet immediately.
If an existing horse shows signs of infection put them into quarantine/isolation immediately and call your vet as soon as possible.
At this point you should start your bio-security plan: restrict human contact, collect all infected rubbish (scabs, hair, disposable towels) and destroy it, disinfect all tack and gear that the horse has come into contact with. Always attend to quarantined horses after you have finished with non-infected horses.
Do not share tack, rugs and grooming gear between horses.
Note: Use disposable gloves when you treat your horse and wash your hands with soap and water after you have finished. Keep your other pets (dogs and cats) away from the infected horse and the quarantine area.
Ringworm in Horses