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Ringworm: A Nuisance for Both Pets and People

Pet Column for the week of June 5, 2006

Related information:

Services - Dermatology
Services - Public Health

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

Ringworm is a highly contagious skin infection that can spread between people and animals, causing itchiness and red circular lesions.

Ringworm is named for the ring-shaped lesions that it leaves on the skin, but the infection is not caused by a worm, but rather by three species of fungi known as dermatophytes.

Dermatophytes may live in the soil or may be carried by cats, dogs, and rodents.

In humans, ringworm lesions appear as red, scaly, ring-shaped sores, and Dr. Karen Campbell, veterinary dermatologist at the University of Illinois Veterinary Teaching Hospital, explains that ringworm usually manifests on pets as circular areas of hair loss.

"You see hair loss first, and then the skin can get crusty with variable amounts of redness, discomfort, and itchiness. The most common site of infection in dogs is on the nose, since dogs usually get the fungus from rooting around in dirt and grass or rubbing up against other animals."

In both dogs and cats, hair loss on the nose or muzzle can spread to rest of face as the animal scratches the skin and spreads the fungal spores.

To diagnose ringworm, a veterinarian can pluck hairs from affected areas and look for fungal spores on the hairs under a microscope. Potentially infected hairs may also be cultured on dermatophyte culture media to allow any spores to grow, so the fungus can be identified.

Treatment of ringworm involves a combination of topical and oral medications. Campbell points out that some antifungal drugs can have harsh side effects on the liver and bone marrow, so a veterinarian may want to perform blood tests while an animal is on antifungal drugs to monitor for side effects. "Also, at end of therapy, we want to re-culture the pet's hairs to make sure the spores are gone and the infection is cleared."

Pets can give ringworm to people and vice versa, and since the infection is highly contagious, owners need to seek proper veterinary care and practice proper household hygiene to limit the spread of the fungus.

As long as lesions are present on either humans or pets, the fungus is contagious. "The most important thing to be aware of is that dermatophyte organisms live on and in the hairs," notes Campbell, "so every hair an infected animal sheds can potentially infect people in the household, or re-infect that pet or another pet."

"Keep in mind that an infected pet is a walking fungus factory, so keep it isolated until the infection has resolved." Infected pets should sleep in a non-carpeted place, such as a bathroom, that can be bleached and disinfected. Owners should wear disposable rubber or plastic gloves when handling infected pets and should wash and disinfect anything that has come in contact with an infected animal.

Cleaning the home to eliminate loose hairs can limit the spread of the fungus. "Owners should thoroughly dust and vacuum carpeting and furniture. Electromagnetic polishes and cloths such as Pledge(c) or a Swiffer(c) on hardwood floors can help trap hairs from corners." Vacuuming does not blow the fungal spores back into the environment since the spores are firmly stuck to the hairs.

The affected areas of a pet's skin should be shaved to remove contagious hairs and contain the infection.

Ringworm infections can be difficult to prevent, but Campbell recommends keeping pets from rooting in soil if possible and keeping them away from other animals with obvious lesions.

Fortunately, ringworm infections stay localized in the skin and do not usually spread to other organ systems. "However, ringworm is definitely a nuisance to both pets and people."

For more information about ringworm infections and your pet, consult your veterinarian.