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Ringworm and Zoonotic Diseases

Ringworm is a common skin infection of dogs and cats. It is actually a fungus not a worm. This fungus also fits under the category of zoonotic disease because humans can become infected with the fungus from their pets (as well as contaminated environments). Pets get infected from other animals or contaminated environments. There are several types of fungal species that fit into the category of dermatophyte. This means that the fungi infect hair shafts, nails and superficial skin layers. This leads to broken hairs as the fungus weakens the hair shafts as well as red, inflamed skin at times. Often, cats and dogs will
have no signs but can spread the infection through contact to other animals or people. The incubation, once contact is made, is usually 1-4 weeks and the fungus can last up to 1 ½ years in a contaminated environment. Wow!

Dermatophyte infections on the skin and hair can look like anything. Sometimes it is itchy, sometimes loss of hair, sometimes scabs, sometimes a brittle, rough hair coat and sometimes nothing at all. Infected animals shed the fungal spores off the coat into the environment to be a source of infection to other animals and people. The very young, the very old, long-haired cats and patients with immune system compromise are the most susceptible. Ringworm is diagnosed with a culture of the fungus on the skin or hair; a small portion of the dermatophyte species will glow under a ultraviolet light. This is called a woods lamp and it can be shined on the coat of a pet that maybe suspected of having a dermatophyte infection to attempt a diagnosis. In some cases, examination of the hair under a microscope may aid in diagnosis.

The treatment is multi-modal with treatment of the infected pet, in addition to contact pets and the environment they live in. Various topical sprays, dips, and oral medications can be used singly or in combination, depending on the case, to treat. The environment must be aggressively cleaned often or the infection can become recurrent in the animals that live in it. Carpets often require a professional cleaning. Discard brushes, blankets, etc. that cannot be disinfected. Dilute bleach is very effective and can be used on items that will not be damaged by the bleach. Replacing furnace filters, cleaning the heat duct plates and cleaning window hangings and blinds are often recommended.

Humans that suspect they are infected are encouraged to seek attention from a physician.

- Ashly LaRoche, DVM

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