Also called:
  • Dermatophytosis
  • Fungus
  • Fungus infection
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What is ringworm?

Although the name “ringworm” implies otherwise, this skin condition is actually caused by a fungus. It can occur in cats, dogs, and most other species of animals including humans.

What causes ringworm?

There are several types of fungi that cause ringworm. They like to live on the skin or hair, but also survive in the environment. Each species has a slightly different habitat and “behavior”. The fungus can be spread among animals by direct contact, but also through infected brushes, rugs, or even airborne hairs. Under certain conditions, the fungus is quite hardy and can survive for a long time in hair and skin debris that have fallen off an infected animal. It may be found at high concentrations where many animals congregate together.

Is ringworm contagious to people?

Yes. The fungus can be spread from infected pets to people and vice-versa. The fungus is also transmitted between animals of different species. It is not always spread by direct contact; contacting infected hairs and other materials may be enough to allow transmission.

Ringworm in cats

Ringworm is common in cats. It causes one or several spots of hair loss, without much itching, often on the face. Young cats and certain breeds (e.g. Persians) are most susceptible to the infection. Occasionally, cats can be “carriers” of the infection without showing any signs of hair loss. Because they carry the fungus on their coats, these cats may occasionally infect other animals and people around them.

Ringworm in dogs

Ringworm in dogs does not often cause the classic round hairless patches that we often see in cats, so it may be more difficult to diagnose. It may look more unusual and mimic other skin diseases. Many other skin conditions are mistaken for “ringworm”, so it is important to make the diagnosis as described below.

How is ringworm diagnosed?

Ringworm is best diagnosed by culture, which means by growing the fungus in the laboratory. Only in this way are we able to differentiate among the various fungal species that cause ringworm. Determining the identity of the fungus helps us decide on the course of treatment and sometimes gives us a clue as to the source of the infection. The culture is easy to collect and requires 1 to 3 weeks for the fungus to grow.

Ringworm can also be diagnosed in several other ways. These include the examination of the hair under a black light or microscope (trichography), or skin biopsies (dermatopathology).

How is ringworm treated?

The pet’s immune system may eventually clear the ringworm infection without therapy. Because of the risk of infection to other animals and people, and because the resolution tends to be slow, we usually recommend instituting antifungal therapy for ringworm.

The treatment of ringworm can consist of both oral medications and topical therapy. Because the fungus is quite hardy, therapy may sometimes continue for weeks to months. Mild cases may need only one of these forms of treatment and may be easier to eliminate. In most cases, the skin begins to look normal and the hair starts to regrow before the fungus is actually eliminated. If therapy is discontinued too soon, the condition may return and the pet may remain “infectious” to animals and people around him.

The oral medications given for ringworm can rarely cause serious side-effects that are difficult to detect on physical examination. For early detection we may recommend monitoring your pet’s blood panels at regular intervals during therapy.

Topical medications for ringworm help to kill the fungus in the areas that are difficult for the oral medications to reach and also reduce the possibility of transmission from the hairs that fall out of the skin. We may prescribe shampoos, dips, and creams for your pet. We may also recommend clipping the hair for the same reasons.

What about treating the pet’s environment?

In any case of ringworm, it is a good idea to treat the environment to reduce the chances of reinfection of the pet, and infection of humans in the household. Although the fungus is quite resistant to many household cleaners, vacuuming and mopping floors and other surfaces is helpful in removing infected hairs. The pet’s bedding should be washed frequently during therapy. The pet should not be allowed to sleep in the owner’s bed until the infection has resolved. Pets should be isolated from immunocompromised people as much as possible.

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