Cats and Ringworm
by Margaret Schill
Ringworm (Dermatophytosis) is a skin fungus, not any kind of worm. There are several organisms that can cause ringworm infections, all members of the Dermatophyte family, so the disease is also referred to as dermatophytosis.
The most common organism affecting cats is Microsporum canis.
The fungus that causes ringworm of the body lives in humans, animals, and soil. The fungus that causes scalp ringworm lives in humans and animals.
Fungal infections can invade or spread to various other areas of the body, and for humans, are named for the affected body part. Tinea cruris (Jock itch) in humans is a form of ringworm that causes an itchy rash on the skin of the groin area. Tinea pedis (Athlete's foot) in humans is also a form of ringworm, causing peeling, cracking, and scaling on the bottoms of the feet and between the toes, along with itching or burning. Neither tinea cruris nor tinea pedis are caused by the most common organism affecting cats. The fungi that cause ringworm of the foot live only in humans.
Ringworm is contagious. It spreads between people when they have skin-to-skin contact with a person or animal that has it. Likewise, people can give ringworm to cats. It can also spread when people share things like towels, clothing, combs, brushes or sports gear. It can be spread between cats from sharing items in the home where pet hair has been left behind by the infected cat. Cats and dogs can spread ringworm to each other. Ringworm spores can be found in soil, and cats can get ringworm from soil. People can also get ringworm from soil, but that is not very common in humans, since humans don't tend to dig in soil with their bare hands. When gardening, people should wear gloves.
Cats with ringworm will often have patches of missing fur, usually on the head, ears, chest, front paws and legs, and the tail. The skin in the infected area will often look dry and scaly. There may be small pus filled bumps, called pustules. People will have a ring of red, circular thickened skin. The fungi eat hair and dead skin, which is what makes the bald patches. Unlike humans, the infected skin on the cat won't usually look red, nor will it be in the classic ring humans tend to show. Ringworm lesions don't usually itch cats, but sometimes they do. The Mar Vista Animal Center's website, http://www.marvistavet.com/html/ringworm.html, shows photographs of a cat and person with ringworm.
Occasionally, the claws of cats can get infected with ringworm, which then results in the claws becoming rough and pitted, with a scaly base.
Sick and poorly nourished cats are more susceptible to ringworm, and younger cats more so than older cats. In both humans and cats, individuals with weakened or immature immune systems (such as in kittens) are more susceptible. Most healthy adult cats have some natural resistance to ringworm and never develop symptoms from the fungus. Same as with humans. According to Dr. Rebecca Hover of the Centenniel Valley Animal Hospital, PC, adult humans with strong immune systems are fairly resistant to ringworm infection, though a break in the skin can allow infection. See: http://www.cvah.com/article/ringworm.html.
If you suspect your cat might have ringworm, take the cat to a veternarian for a correct diagnoses. To determine if a cat has ringworm, a vet will use a special ultraviolet lamp, called a Wood’s lamp, in a dark room to examine the cat. Ringworm will fluoresce in many cases, but not all. The Wood’s lamp is a screening tool. To verify that ringworm is present, samples of hair and skin are cultured. Ringworm is not the only cause of hair loss in cats, so vet diagnoses is needed. Ringworm cannot be diagnosed by simply looking at a lesion.
Ringworm will self-cure in about 5 months, but treatment is desired until it passes on it's own as the cat can infect other animals and people who touch the cat or it's hairs in the environment.
Treatment for cats consists of oral medications and a topical cream, ointment or shampoo containing an antifungal. A special shampoo named Malaseb, containging Miconazole and chlorhexidine, has been shown to be effective against ringworm. Cats should be bathed twice weekly. For the shampoo to be effective, it is important that there be a contact time of 10 minutes with the cat’s fur. This can be a difficult thing to accomplish, depending upon the cat. The oral medications work by inhibiting fungal reproduction rather than by directly killing the fungus. The topical therapy actually kills the fungus on the pet so that the hairs dropped will not be infectious. So, both oral medications and topical treatments are desired.
Cats receiving treatment for ringworm usually show good improvement within 2 to 4 weeks of therapy. However, treatment should not be discontinued until a fungal culture show the ringworm is gone.
Over the counter topical products for humans include Lamisil (terbinafine) and Lotrimin (clotrimazole). Do not use products for humans on cats without a veterinarian directing you to do so. Some products fine for humans are toxic or irritating to cats.
Warning!! Tee tree oil is sometimes said to help cure ringworm in humans. NEVER use tree tee oil on cats because it is HIGHLY toxic to cats.
Thorough housecleaning is needed to get up as much shed hair and spores as possible. If a cat in the home has ringworm, the infected cat would best be confined to one area of the home to reduce spreading of the spores throughout the entire home. The spores can live for months and can be spread from bedding, toys, grooming implements, etc., so those items need to be cleaned as well. Bleach diluted 1:10 will kill 80% of fungal spores, so any surface that can be bleached, should be bleached. Carpets and stuffed furniture need to be vacuumed and floors mopped frequently. Drapes should be washed or vaccumed. The vacuum cleaner bag should be disposed of promptly. If using a bagless vacuum, be sure to wash the canister with a bleach solution after disposing of the contents. Avoid sweeping with a regular broom and avoid dry dusting with dusting clothes or feather dusters, since that may actually spread spores through the air. Instead, use a Swiffer-type broom and dust cloths. Dust and pet hair sticks to the Swiffer dusting clothes, instead of spreading the dust around.
In consideration of stray cats outdoors, if one does not touch any cats with hair loss with bare hands, one won't contract ringworm from the cats. Bits of fur blowing on your porch, for example, will not spread ringworm to you if you do not touch the fur with your bare hands. And the fur might not be infected anyway.
Links with information about ringworm:
Information regarding ringworm and cats:
http://www.fabcats.org/owners/skin/ringworm.html (has picture of cat with ringworm on the face)
Ringworm information geared towards humans: