Skin Disease in Cats: What is Ringworm?

Ringworm is the most common infectious skin disease in cats. It is caused by a fungus orringworm1 300x207 dermatophyte, not a worm, and is highly contagious to other animals as well as people. The most common dermatophyte isolated is Microsporum canis, followed by Microsporum gypseum and Trichophyton species. Ringworm is diagnosed more frequently in cats obtained from shelters, catteries, or feral cat colonies. Infection occurs after fungal spores are contracted directly from other animals or from contact with contaminated soil, bedding, or grooming tools.  Infection results in patchy hair loss and crusting or scaling of the skin. It rarely causes cats to scratch.

How is Ringworm Skin Disease in Cats Diagnosed?

Ringworm in cats can be diagnosed many ways. Your veterinarian can use a Wood’s lamp where ultraviolet light causes affected hairs to fluoresce bright green. About half of the Ringworm species will fluoresce. Another diagnostic method involves examining hairs under the microscope lens. Spores and hair destruction may be seen this way. The best was to diagnose Ringworm skin disease in cats is to send hair samples to the laboratory and have a fungal culture performed. This will identify the presence of a fungal infection as well as the species of Ringworm present.

Treatment of Ringworm Skin Disease in Cats

Cats with Ringworm can be treated in a variety of ways. Oral medication is the easiest but the most expensive. Sporanox, or Itraconazole, is probably the most commonly used medication. It has minimal side effects which include nausea, vomiting and diarrhea. It can be toxic to the liver so monitoring of liver enzymes is important. Terbinafine is another oral medication used which has the same cost and effectiveness as Sporanox.  Griseofulvin can also be used, but it has more severe side effects including bone marrow suppression and liver toxicity. These side effects are worse in kittens and immunocompromised cats.

Cats with Ringworm can also be treated with topical medication. It is controversial as to whether clipping all of the cats hair is beneficial but if topical treatment is ineffective, this may be recommended. Lime-sulfur dips, performed twice a week, will treat cats with ringworm. This dip has a terrible odor and stains clothing. Trying to apply a dip to a cat twice a week for several weeks may be challenging to a cat owner as well!

Ringworm skin disease in cats may resolve without any treatment in two to three months if the cat is healthy and has a good immune system. The concern with leaving cats untreated is that they can infect other animals and humans in that period of time.

Ringworm Skin Disease in Cats: Concern for People

Ringworm is contagious to other animals as well as people. Children, the elderly, or people who are stressed or have compromised immune systems are susceptible. If an infected kitten or cat lives in a household with a person who falls into one of these groups, every effort must be made to treat the cat as well as the environment. The cat should be isolated to one room in the house. Daily cleaning and vacuuming is required. Dilute bleach solution will kill fungal spores on hard surfaces like floors and window sills. Carpet will require steam-cleaning. Bedding should be washed frequently in hot water. Air filters will need to be changed if there are vents in the room where the cat is being housed.

When is Ringworm Skin Disease in Cats Cured?

Cats with ringworm are considered cured when three fungal cultures, performed every two weeks, are negative. These fungal cultures are begun after the fourth week of treatment, so one can see that treatment of affected cats can take over two months.

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Dr Jill Christofferson

Jill Christofferson, DVM is an experienced veterinary general practitioner. Her professional interests include ophthalmology, dentistry, and reproduction.

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