Ringworm (also known as dermatophytosis) may sound like a worm or parasite but it is actually a fungus which lives on keratin (found in skin, hair and nails). Three species of ringworm are commonly found to infect felines. These are Microsporum canis (this is by far the most common cause of feline ringworm), Trichophyton mentagrophytes (usually contracted through contact with rodents), and Microsporum gypseum/fulvum (these are usually contracted from contact with spores in the soil).

Ringworm is spread through contact with another infected animal or through contact with the actual fungal spores (called arthrospores). When an animal is infected with ringworm sheaths of arthrospores are produced and can be found around the infected areas (hair strands, skin, or nails). These spores then scatter throughout the environment, and can be found in carpeting, furniture, cat bedding and even in your air filters. The spores are also very resistant and can live in the environment for up to 18 months. This is why treatment for ringworm must also include a thorough house cleaning to rid the home of any spores that could reinfect you or your cat. This can be done by disinfecting your home using a dilute chlorine (.5%) bleach solution (this must include all furniture, carpeting etc.). Remove and replace all used air filters in the home. Thorough vacuuming of the carpeting and subsequent removal of the vacuum bags can also assist in ridding the home of spores. And if you can, throw away any pet bedding, toys etc. that may be contaminated. If you can not dispose of such items make sure to clean them very carefully with the disinfectant solution mentioned above.

As well as being fairly contagious to other cats (and dogs although dogs get it less frequently than cats), ringworm is the most common zoonotic disease, meaning that it can be transferred from animals to humans, and its rate of infection is rising. So if your pet has ringworm you must take certain precautions to protect yourself, such as using gloves to handle your pet, and wearing an apron or clothing that you wash subsequent to handling the pet.

Cats can be asymptomatic carriers so if you have multiple cats, or other pets and one pet has ringworm but the other seems symptom free… you may want to have him/her tested as well just to be cautious.

Ringworm is generally seen in kittens before their immune system is fully developed or in adults who have been immuno-compromised by stress, disease or disorder.

Symptoms to look for:

  • Loss of hair in circular patterns
  • Hair loss in irregular patterns
  • Scaly skin
  • Redness or itchiness
  • Deformed nails and claws


Ringworm is often a self-limiting disease meaning that it can clear up on its own in a few months. However this is not always the case (especially if your cat does not have a healthy immune system) and thus medication is given to help the body heal faster and to help to stop spread of the fungus.

If you suspect that your cat has ringworm take him/her to the vet immediately. Your vet may use a Woods Lamp test, in which a bit of infected hairs/skin/nails is placed under the lamp. Areas infected with M. canis will ‘glow’ (this is not foolproof, as only M. canis glows under the lamp). Your veterinarian can also directly examine hair or skin under a microscope. This is a rapid and easy way to determine if your cat has ringworm, however it does require a bit of expertise on the examiner’s side as the fungal elements are small and sometimes difficult to distinguish. The most reliable way to be positive that your cat has ringworm is to take a skin scraping and perform a fungal culture on it. This is usually done by sending the sample to an outside diagnostic lab.

Treatment is usually given through applying topical antifungal solutions or giving oral medications. Current findings show that oral medications, no matter what the severity of the case, work best at treating and stopping the spread of ringworm. Medicated baths, dips, sprays or shampoos may also be given. Be patient if your cat has ringworm, successful treatment can take weeks to months to fully rid your pet of ringworm. And the only way to be certain that your cat is fungus free is to have him/her retested by your vet. Finally, as stated earlier, you must be aware of the risk of infection to you and other pets in your home, as well as the steps you must take to clean your home of any spores that may be present and which could cause reinfection.

Precautionary measures:

The best prevention is keeping your cat in a clean environment and away from other cats or animals which may have ringworm. Also if your cat does have ringworm make sure to thoroughly clean your home and have all other animals in your home tested/treated to prevent reinfection.