Ringworm is an extremely frustrating syndrome.
Ringworm is not a worm. It is a fungus. The fungus is ubiquitous. It can spread from pets to people, and vice-versa. It also can be contracted from the environment. It is almost impossible to eliminate ringworm from a contaminated area.
The fungi that cause ringworm often cause a red, circular rash on the skin of infected humans. The rash looks like a worm under the skin. This is the origin of the name. In animals, ringworm may cause hair loss, scabbing, red skin, or itching.
A black light can be used to diagnose some forms of ringworm. Microscopic evaluation of specially prepared hairs is used in other cases. The most reliable method of diagnosis involves plucking several hairs from a suspected lesion and using a special culture plate to isolate the fungus. This process can take up to ten days to yield a diagnosis.
It is not possible to diagnose ringworm through visual evaluation of a suspected lesion.
In my experience, ringworm is overdiagnosed in pets. Children often catch the disease at school (or in the garden), and pets often are wrongly held to blame. In my experience, pets are as likely to contract ringworm from people as the other way around.
That said, it is possible for pets to spread ringworm to humans. Any pet with a suspicious skin lesion should go to the vet for a ringworm culture.
Go to my web site for more information on ringworm:
Photo: Caroldermoid. [Note: I am not convinced the cat in the photo has ringworm. Allergies are more likely.]