Ringworm is often seen in cats, even indoor cats. But despite the name, it doesn't involve any worms. Thankfully, this highly contagious and non-life-threatening infection is avoidable and treatable if you know what to do.
What Is Ringworm?
Ringworm is a fungal infection that infects many different species of animals. It's also referred to as dermatophytosis. In cats, about 98 percent of ringworm cases are caused by the fungus Microsporum canis. Cats are often infected with this fungus since it's easily transmitted. Ringworm affects the top layer of the skin and occurs when the fungi or its spores make contact with a cat's skin. It's very similar to other fungal infections, such as athlete's foot.
Signs of Ringworm in Cats
Ringworm lesions create hairless, scaly, red rings on the skin. They're also often quite itchy. These round lesions usually appear on the front legs, ears, or other parts of a cat's head but can pop up anywhere, especially in severe infections. You'll notice ringworm when petting your cat. You'll first see a small patch of hair loss, and then upon further examination, you'll find a red ring in this patch of hairless skin.
Causes of Ringworm
Cats can carry the fungal spores of ringworm and show symptoms of the disease, or not show any symptoms at all. Spores can spread to other cats quite easily, either directly or indirectly. Your cat can get an infection when in direct contact while touching another animal who has ringworm. Your cat can get ringworm indirectly by simply touching the bedding, food and water dishes, toys, and other items that a carrier or infected pet has come in contact with.
Can You Get Ringworm From Your Cat?
Ringworm is a zoonotic disease, which means it can spread from an animal to a human. A ringworm infection in a person typically occurs after a person has pet an infected or carrier cat, but it can also occur after simply handling items that were used by an infected cat. Immune-compromised individuals, such as the elderly and very young, are more prone to contracting ringworm.
How to Diagnose Ringworm
To confirm that a round lesion is ringworm and not another type of hair or skin issue, your vet may perform tests for a diagnosis:
- Wood's lamp: A special black light called a Wood's lamp causes the fungus to glow a yellowish-green color. It's a simple and non-invasive test to perform, but it's not always accurate. The lamp could make other things glow, including dead skin cells, topical ointments, and other fibers, so it's just one test used for evaluation.
- Microsporum: Your vet can look for fungal spores, called Microsporum, under a microscope. A piece of clear tape placed on the lesion picks up cells that can then be stained. A special purple stain causes the ringworm spores, which look like small ellipses with lines in it, to be visible under a microscope. The spores can still be hard to see even with this test.
- Culture: One of the most accurate ways to diagnose ringworm is to take samples of your cat's fur and skin and place them on a special culture medium to see if the fungus will grow. It's a very slow method that takes over a week for results.
- Biopsy: A skin biopsy is the most invasive way to diagnose ringworm, but it's also very accurate. This method involves cutting out a piece of skin and sending it to a lab for microscopic analysis. It can take several days to get results.
- PCR: The newest method to detect ringworm is through a non-invasive polymer chain reaction test, more commonly referred to as a PCR. Like the culture test, the PCR test uses skin and hair but can detect ringworm in only a few days.
These different tests will verify that your cat has ringworm. Your vet will then be able to treat the fungal infection with appropriate medication. Your vet may also ask you if you have any lesions that look similar to your cat's lesions, as another indication of this zoonotic disease.
Ringworm May Mimic Other Diseases
Ringworm lesions can look similar to other issues, which is why it may be necessary for your veterinarian to run more than one test. For example, fleas and mange (both the demodectic and sarcoptic types) can cause hair loss and itching. Some cats will lick their fur off and irritate their skin until it's red due to allergies or stress and anxiety. A misdiagnosis can mean your cat will be given the wrong kind of medication.
How to Treat Ringworm
If your veterinarian has diagnosed your cat with ringworm, they'll likely prescribe an anti-fungal medication to treat the infection. Itraconazole is a medication frequently used medication for pets with ringworm. But due to the size of the capsules, it typically has to be compounded into a liquid solution in order to dose it for a cat.
Sometimes topical ointments are used to treat ringworm in conjunction with oral treatments. By using both oral and topical treatment regimens, you'll kill both the spores on the skin and suppress the infection in the cat systemically.
Finally, if you have a cat with ringworm, you'll need to treat your home environment in order to kill any remaining spores. Use the correct ratio of diluted bleach solutions on surfaces after your general cleaning routine in order to kill the spores of the ringworm fungus. Keep the bleach solution in contact with a surface for a full ten minutes to ensure that the area is disinfected.
How to Prevent Ringworm
Ringworm is highly contagious in cats but it's also preventable if the appropriate steps are taken. Washing your hands before and after handling your pet is the easiest way to decrease the likelihood of you or your cat from becoming infected with ringworm. Aside from that, don't let your cat play with cats that don't live within your household, maintain a sanitary living environment for you and your cat, and if you have ringworm, refrain from touching your cat until your doctor has determined that you're free of the infection.
Ringworm (Dermatophytosis) In Cats. Merck Veterinary Manual, 2020.
Ringworm: A Serious But Readily Treatable Affliction. Cornell University College Of Veterinary Medicine, 2020.
Ringworm In Cats. VCA Animal Hospitals, 2020.