Ringworm in cats isn't actually a worm at all. It's a fungus that shows itself on an infected animal (or person) in a distinctive ring shape. Ringworm is also a zoonotic disease, which means it can pass between pets and people.
Cat Ringworm Symptoms
The most common symptom of ringworm is a small, round patch (or ring) of skin that lacks hair. This bare circle usually has a scaly center. These rings are most commonly found on a cat's head, ears or tails. When ringworm infects a cat's face, the bare skin patches aren't usually round, but they spread across the animal's chin, lips or nose and resemble other skin conditions.
Sometimes, a cat's entire body is affected by ringworm, making her coat appear greasy or scaly. In other cases, the first indication that a cat has ringworm is when she sheds excessively or develops misshapen nails.
Ringworm Symptoms in People
The most common symptom of human ringworm is a scaly red ring on the skin that can grow as the infection spreads. If the infection spreads, the center of the red ring will appear to clear while new rings form at the edge of the original infection. Human ringworm infection is treated with antifungal creams that are used as directed by your physician.
Cat Ringworm Diagnosis and Treatment
Your veterinarian may use one of a variety of tests to diagnose your cat's ringworm. One of these is to place the cat under a Wood's lamp and view her skin under a special black light that causes the ringworm fungus to appear fluorescent. This test may or may not detect the presence of ringworm since not all ringworm fungi appear fluorescent under the Wood's lamp.
Another diagnostic test involves removing hairs from the edge of the ring and looking at them under a microscope, but the most reliable test may be to collect a small sample of affected skin and test it for the presence of fungus.
Once a diagnosis has been made, your veterinarian can devise a treatment plan. In mild ringworm cases on shorthaired cats, treatment will probably involve the application of an antifungal cream over the course of a few weeks. In more severe cases, oral medications may supplement the topical creams, along with special lime sulphur dips. If your cat is longhaired, she may need to be shaved for the topical treatments to be fully effective.
When a Cat Is No Longer Contagious
After you've begun treating your cat, she will still be contagious for about three weeks, and the length of time that she's contagious will depend on how strictly you follow the treatment plan prescribed by your veterinarian.
Wash and disinfect your cat's bedding with a bleach-and-water solution, and discard any chew toys or other cloth items that cannot be washed and disinfected. Also clean and disinfect your cat's grooming tools to ensure the fungus isn't spread to other pets in your home.