Sandra R. Merchant, DVM, Diplomate ACVD
Carol S. Foil, DVM, Diplomate ACVD
Ringworm is a term commonly used for fungal infections of the skin and hair. These infections may occur in both animals and man. Some fungal organisms live only on animals or man, while others live primarily in the soil. Infections can occur following direct contact with infected animals or humans, or with materials that have been in contact with infected animals or digging in soil contaminated with these fungal organisms. In general, younger animals or immune-comprised animals are more susceptible to infection. Cats, however, are usually susceptible.
Ringworm infections are not always circular as suggested by the name. Lesions can assume almost any pattern of hair loss and scaling. Sometimes (especially in cats) hair loss is not prominent but small crusty bumps are felt on the skin. Some animals will be infected with ringworm but not show any changes in the hair or skin. These are "carrier" animals which means they can transmit the fungal infection to other animals without showing any signs themselves.
It is important to remember that ringworm can be transferred from animal to man (and vice-versa). Many times red circular itchy areas will appear on the skin of people who have infected animals. If this occurs, a physician should be consulted.
Diagnosis is made by culturing hair and scales for the fungal organism. Culturing takes from 10-21 days to grow the fungus. Occasionally a tentative diagnosis can be made on the spot with a "Wood's" lamp examination or microscopic examination of plucked hairs.
Small localized infections may only require clipping and/or spot application of a topical medication. More generalized infections may require long-term oral medication and bathing or rinsing with antifungal agents. Rarely total body clipping is required. In cats, fungal infections may take months to clear. Recheck appointments are very important.
Medications that may be chosen for your pet include griseofulvin (Fulvicin®, Gris-PEG®), itraconazole (Sporanox®), or terbinafine (Lamisil®). Most of these have the potential to cause some side effects, so blood tests may be needed for monitoring during treatment.
You should keep your pet isolated from contact with other animals and children and wear gloves when handling your pet. The environment should be thoroughly cleaned and disinfected to prevent reinfection. Thorough vacuuming and cleaning with dilute (1:30) household bleach are helpful. Other pets in the household should be checked for infection.