Ringworm is one of the most common skin disorders of the cat. Cats under one year of age are more often affected than other animals. Ringworm is not a worm but a fungus that invades the most superficial, outer layers of skin, nails, and hair. Ringworm fungi usually do not invade living tissue unless the cat has an allergic reaction to it. In these cases it can produce deep skin infections and even spread to involve other organ systems.
The most common sign of ringworm is characterized by hair loss in a circular area but ringworm can appear in many other ways-scaly patches, irregular hair loss, crusts, and discolored, deformed toenails. Areas of reddened or darken skin or small scabby bumps may also indicate ringworm. A ringworm infection can be present with no evidence of skin disease at all!
Many uncomplicated cases of ringworm heal spontaneously in one to three months, however, you need to remove it from your environment also. The ringworm fungi are attached to the hair follicles, which is why it is thought to be airborne. Care should be taken when cleaning an area that has been exposed to ringworm so as not to spread it further by disturbing the hair follicles or spores.
The first step is to determine if your cat or kitten has ringworm. An ultraviolet light can be used to detect the most common type of ringworm, Microsporum canis, which may fluoresce green. If you suspect ringworm and it does not fluoresce green under an ultraviolet light then microscopic examination of skin scrapings and/or a fungal culture may be necessary. Infected cats should be isolated from other uninfected animals to avoid spreading of the infection.
Topical treatments include bathing with a 2.5% lime sulfur dip every seven days. There are several ringworm shampoos sold at pet stores which also may be used but are not as effective as the lime sulfur. Products containing 2% micanzole nitrate or 1% clotrimazole, which inhibit the growth of ringworm, can be purchased in a drugstore without a prescription and should be applied twice daily.
Other anti-fungal drugs are also available from your veterinarian that can used for the treatment of more serious ringworm cases; they are incorporated into new hair growth to prevent recurrence of the fungus. Vaccines against ringworm can help eliminate signs of infection, but are no substitute for thorough treatment of infected cats.
Clean your house thoroughly and change any air filters. Carpets should be steam cleaned. Wash and disinfect or discard your cat’s bedding, toys, scratching posts, collar, harness, and/or leash, and grooming equipment.
A cleaning solution of one part bleach to 10 parts water is an effective disinfectant that can be mopped or sprayed onto surfaces. Cleaning should be repeated weekly until the cat is fully cured. Untreated ringworm spores may survive in dry environments as long as 2 years.
Almost all shelters have an outbreak of ringworm at one time, as do most rescue volunteers who take in animals, but with extensive cleaning it is not catastrophic unless you are a breeder of long-haired cats.