9539 Liberty Road, Frederick, MD 21701
Phone: 301-898-4009 ~ Fax: 240-668-3664
Gentle, complete veterinary care for the felines in your family
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Ringworm is not a worm, like the name suggests, but a fungus (a dermatophyte) that invades the most superficial layers of the skin. Ringworm is the most common infectious skin disease in cats and can be transmitted to humans. It usually does not cause serious systemic illness but can be quite a nuisance because it survives so well and takes a long time to completely treat.

The fungus is most commonly found on an infected animal, the living environment of these animals, and in the soil outside. The spores of the fungus are very hardy and can live in the environment for 18 months or more. They live and replicate in the hair follicles so it is more common in animals (cats, dogs, horses, etc) than people.


Ringworm is transmitted through direct contact of infected spores to an animal. It is most common in kittens, long haired cats and cats that may have trouble grooming themselves (overweight). This is due to the fact that younger cats and overweight cats have weaker immune systems. Grooming is also very important since the licking removes the spores from the hair. Grooming is particularly hard for heavier cats and long haired cats. Any prior lesions on the skin will add in the rapid germination of the spores. Cats with fleas, lice and mites are very susceptible to infection.


Cats with ringworm usually have small round patches of hairless, dry, scaly skin. These lesions tend to appear on the head, such as the tips of the ears, and on the body, particularly the paws and tail. If left untreated, the lesion(s) will continue to grow. The lesion may or may not be itchy.


The ringworm PCR test usually gives us a diagnosis within 3 days, but if a positive case seems likely, we'll start treatment sooner. This is usually with terbinafine, a medication mixed with wet food. In more severe cases, we will recommend a series of lime dips (baths with a sulfurated lime solution) once a week and perform a culture of the infected area. Regardless of the treatment, the affected area is cultured again just to make sure the fungal infection has cleared up.


Because ringworm spores can survive for such prolonged periods of time in the environment, certain measures should be taken to prevent re-infection and spread of the disease. The spores are associated with cat fur so vacuuming is a great way to minimize the presence of this fungus in your home. Carpets should be steam cleaned and disinfected. Clothes or bedding in contact with infected cats should be laundered. The spores are resistant to most household cleaners, but dilute bleach (1:10 dilution) will kill it. For serious long-standing problems you may need to have ventilation ducts and furnaces professionally cleaned. Furnace filters or any other device that traps fur should be cleaned or replaced.
People should wash their hands and change clothing every time they handle the infected cat and, if dealing with a multi-cat household, the infected cat should be isolated from the healthy ones. Many people that are exposed to ringworm either donā“ get infected or get a mild infection that is treated with a topical ointment, and it is not a disease that causes internal problems. Transmission from people to animals is very uncommon. Animal to person transmission is more common because of the more severe nature of the animal form of the disease.