Heubner-Ridder Veterinary Hospital

Ringworm, Pets and People

Ringworm, also called dermatophytosis, is a fungal infection that occurs in the skin, hair and nails. The fungi feed on the keratin that is found in the outer layers of these structures.

Ringworm infections can occur in all domesticated species of animals. There are a number of distinct species of dermatophyte fungi and some are capable of spreading from animals to humans.

The common name of ringworm is somewhat misleading, in that it is not an infection caused by a worm, and the infected areas are not always ring-shaped. In people, a ringworm infection usually starts as an itchy patch of skin that will expand outwards in a ring-like pattern. As it expands, the middle of the patch will heal while the edges will be inflamed and red.

In dogs, the infection may sometimes look the same as it presents in humans, but more often it appears as one or more bald spots on the fur. In cats, a ringworm infection may appear as a patch of baldness, but often the only symptom is some flaky dandruff. Some animals and people can be "asymptomatic carriers" of ringworm, meaning that they have the fungus on their body but do not show any symptoms.

Ringworm is contagious, and can be passed between animals or people by direct skin contact or by contact with contaminated objects such as combs, bedding, food bowls, furniture, or other environmental surfaces.

Contact with ringworm does not always mean that an infection will develop. The age of the exposed person or animal (young and old are more susceptible), whether they have other health problems, immune system weakness or skin sensitivities, and the level of exposure (the amount of environmental contamination that is present), are important factors in the development of a ringworm infection.

A ringworm infection is confirmed by culture of the fungus in a laboratory, followed by identification of the specific species of ringworm causing the infection. A positive culture can sometimes be confirmed within a couple of days, but in some cases the ringworm spores may be slow to grow. Therefore, a suspected sample cannot be called negative for at least a month. A special type of ultraviolet lamp called a Wood's lamp may cause some ringworm fungi to fluoresce, but this test is not always accurate; this test is sometimes used as a rapid screening test in multi-animal facilities, and suspect cases can then be confirmed by culture.

Treatment of ringworm in animals is always necessary to avoid spread of the infection to children or other pets. In an individual case, a prescription of antifungal medication will be administered to the pet, combined with clipping or shaving the hair from the infected lesions to minimize further environmental contamination. In some cases, it is necessary to completely shave the animal's fur. In minor cases, an antifungal cream, ointment or shampoo will be prescribed for application to the localized areas of infection for a treatment period of several weeks to months. In the majority of cases, effective treatment requires the use of oral antifungal drugs for a minimum of six weeks. In all cases, the household must be thoroughly cleaned to eliminate any environmental source of re-infection. In a multi-animal environment, treatment can be extremely challenging and costly.

For further or more specific information about ringworm and your pet, please see our handouts on ringworm in the Pet Health Section of our website, or call the clinic during business hours to speak with one of our health care team.