Many years ago, I had my first run-in with ringworm when my German shepherd (age 12 at the time) developed ball patches. A dozen years later, my second personal experience happened when I adopted a stray kitten I named Seren. She had couple of crusty bald spots on her forehead. That’s actually pretty typical. Cat ringworm has nothing to do with normal shedding. Ringworm most commonly affects elderly or young pets.

Ringworm is not a worm, it is a fungal infection of growing hair, dry skin, and sometimes the nails. There are many types, but about 95 percent of feline ringworm cases are caused by Microsporum canis. The condition also affects dogs and people.

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WHAT IS RINGWORM?

The name comes from the ring-like lesions typically seen in human cases. Ringworm is a kind of biological contact dermatitis in which skin inflammation is caused by a substance produced by the fungus. The inflammation makes the skin inhospitable for the fungus, so it moves on to greener pastures. In people, the fungus grows outward away from the initial central inflammation in ever-widening rings, leaving the center to heal.

In cats, sores also grow outward from the infection, but rarely produce the ring pattern found in people. Ringworm in cats can look like a variety of other feline skin diseases, but hair loss is the most usual sign. Bald patches may develop in only one area, several spots, or cover the entire body. Ringworm is the most common cause of hair loss in kittens. It has nothing to do with normal cat licking or overgrooming where cats lick themselves bald through stress.

The fungus, called a dermatophyte, lives only on hairs that are actively growing. Infected hairs eventually break off rather than fall out, leaving a stubby appearance to the coat. Mild to severe scaling or crusty sores typically develop with varying degrees of itchiness.

HOW DO PETS GET RINGWORM?

Cats and dogs are usually infected by coming in contact with infected hair, but ringworm can also be spread by contact with contaminated grooming equipment or from the environment. Contaminated hairs that are shed into the environment can remain infective for months, and provide a reservoir for reinfection of recovering cats.

All cats can get ringworm, and the length of haircoat has nothing to do with the risk. Both longhaired and shorthaired cats are equally affected. However, the most common victims are immune-compromised, young, and debilitated pets. Puppies and kittens are affected most frequently. Some cats carry the organism without showing signs themselves, and spread ringworm to other cats and pets. If one pet in the household is diagnosed, all should be treated whether they are showing signs or not.

DIAGNOSING RINGWORM

Ringworm in cats is diagnosed by identifying the fungus. The veterinarian may use a Wood’s Lamp to screen suspect cases; about half of M. canis cases will “glow” when exposed to its ultraviolet light. More cases are identified using a culture test which grows the ringworm fungus. A sample of debris brushed from the cat’s skin and fur is placed in a special medium designed to grow certain ringworm species. It may take up to three weeks before the test indicates a positive result.

RINGWORM TREATMENT

During treatment, infective animals should be quarantined from those not showing symptoms. Otherwise healthy cats tend to self-cure in nine months to a year, but during that time, can continually expose other animals (and people) to the fungus. People who are immune compromised, very young or very old are at highest risk.

Shaving ringworm-infected cats to aid treatment used to be routinely recommended but today is based more on the individual situation. Shorthair cats with fewer than five areas of infection may be effectively treated without a full body clipping.

Topical preparations of miconazole are helpful, but medicating the lesion before diagnosis may interfere with proper diagnosis. Miconazole alone or in combination with chlorhexidine is effective. Cats typically are bathed twice weekly, ensuring the product remains at least ten minutes on the cat’s fur. Treat only after your veterinarian diagnoses the condition, and follow his or her recommendation.

Drugs that have been shown to be effective include griseofulvin, terbinafine, ketaconazole, and itraconazole. After ingestion, the drug is incorporated into the growing hair where it slows the growth of the fungus. Pills are usually given once daily for four to eight weeks, and should be continued two weeks beyond the time symptoms have disappeared. A vaccine is also available that may reduce the symptoms of the disease, when used in combination with other therapies.

DEALING WITH RINGWORM AT HOME

Ringworm fungus can live in the environment for well over a year, where it can continuously reinfect cats. For that reason, this infected environment must also be treated; however, fungal spores are difficult to eliminate. Studies indicate that common disinfectants like chlorhexidine and water are not effective. Concentrated bleach or one percent formalin (a formaldehyde solution) have been shown to be effective, but neither are very practical in a home environment.

Daily cleaning of all surfaces using a diluted bleach solution (one part bleach to ten parts water), along with thorough vacuuming is the most effective and practical environmental treatment for most cat owners. Dispose of the vacuum bag by sealing in a plastic garbage sack and removing it from the house.

Has your cat (or dog) ever had ringworm? How did you handle it? Do tell! Now, for catteries and shelters, it can be even more of a challenge–any tips for those folks?