“Your pet has ringworm.” Those are words that conjure images of grimy living conditions, sores and patches of hair loss springing up on everyone within a 200 mile radius of the affected animal. The most upsetting part of the diagnosis is that ringworm is a zoonotic disease, meaning that it can be spread from animals to people. Fortunately, the reality of ringworm is not quite as dramatic as what is generally imagined.

The “worm” part of ringworm is really a misnomer. Ringworm is a fungal infection of the skin and hair that in people tends to cause red spots that spread outward in a circular pattern leaving a clear spot in the center, thus forming a red ring on the skin. In animals the visual appearance of a ringworm infection can much more variable, ranging from patches of hair loss where the skin may be flaky or scabby to a more diffuse pattern of generalized itchiness. Of course that description would also be accurate for about 300 other skin conditions that are not ringworm, so just because an animal has an itchy or crusty skin condition does not mean that it is ringworm or even likely to be ringworm.

There are a number of ways to separate ringworm from other common skin problems. The first is patient type. In this area ringworm is not very common. Although adults certainly can develop ringworm, we see it much more commonly in very young animals, and it is much more common in cats than it is in dogs or other mammal species. Persian cats in particular seem to have a reduced resistance to ringworm.

When we suspect a patient has ringworm the first diagnostic test is to look at the affected areas under UV light--also known as using the CSI “clue wand”. Some types of ringworm cling to the hair shafts and flouresce brightly when exposed to ultraviolet light. If the quick and easy diagnostic test doesn’t yield results and ringworm is still on the suspect list we will gather some hair samples and start a fungal culture on a special growth medium that turns red in a few days in the presence of the ringworm fungus.

When we get a positive result there are several effective ways to treat ringworm. If it is completely ignored most animals will eventually get their immune systems to wake up and figure out how to kick the ringworm on their own. Unfortunately that may take a few months, and in the meantime they are dropping infected hairs around the house that may serve as sources of infection to other people and animals living there too. Long haired animals, like Persian cats, tend to recover faster and shed less contaminated hair into the environment if they are shaved. This also makes bathing with an anti-fungal shampoo more effective. In animals that don’t respond to topical treatment, or who are likely to send you to the emergency room if you try to bathe them, there are oral medicines that can also be quite effective.

I recently read an article in a veterinary magazine that suggested owners buy a dedicated vacuum cleaner and vacuum the house every day during treatment to remove any contaminated hairs from the environment and then throw the vacuum cleaner away at the end. I don’t know that that sort of extreme is usually necessary, but I suppose if you have a very immunosuppressed individual living in your house it may help. Basic common sense--like not having an affected animal sleep on your pillow, in your bed, or on your face--will usually keep your contact with infected hairs low enough to prevent problems.

Resolution of the ringworm infection is proven by a negative repeat culture rather than just resolution of clinical signs because cats in particular can sometimes be asymptomatic carriers of ringworm. In fact, if a human family member is suddenly developing ringworm spots with no known exposure it may not be a bad idea to check the cats in the household even if they aren’t showing clinical signs themselves.