American Fancy Rat & Mouse Association

This article is from the WSSF 2005 AFRMA Rat & Mouse Tales news-magazine.


Ringworm on Mice

Charla Hollingsworth, Houston, TX, e-mail
Q I have gotten ringworm. I have 5–6 patches. I have had the first patch for at least a week. I am not sure if I got them from a student or from my mice. My questions have three strands.

  • First, how can I determine if the mice are the cause of the ringworm. I do not have much faith in the small animal vets here locally. What would a ringworm patch look like on a mouse? If the animal has it, how is it treated?
  • Second, while I have the ringworm patches, what can I do/not do with my mice? When I clean the cages, I have my students hold the mice but I still have to touch the housing equipment.
  • Third, with 5–6 patches on me, is it advisable to go to the doctor? I am treating the patches with Lotrimin and taking Benadril for itching. I am worried that if I go to the doctor they will think I’m stupid.

Thank you for your answers in this matter.

Answer from Lorryta Bowker
A In answer to your questions about ringworm, first, it will look the same on your mice as it does on yourself. Since you have the ringworm, you could be spreading it to the mice if they do not have it. If you got ringworm from your mice, it is not good for your students to be handling them as ringworm spreads easily. If the mice have ringworm, your students could get it from them. If you’re not sure, try wearing surgical gloves when handling them or cleaning out their cage. If the students have to handle the mice, have them handle them in the same way just as a precaution until you know for sure whether or not they have ringworm. Throw the gloves away after using them.

You need to determine whether your mice actually have ringworm or not, so you should take them to a local veterinarian.

Answer from Carmen Jane Booth, D.V.M., Ph.D.
A “Ringworm” is the old-fashioned and not really correct name for having a superficial fungal infection of the skin (Dermatomycosis). The most common dermatophyte in mice is Trichophyton mentagrophytes although Microsporum canis and other fungi have been isolated. Fungi are everywhere in the environment. In most cases, it is young animals that are affected where their immune system is not yet developed enough to resist the fungus. In most cases, the fungi cannot infect intact skin and some type of skin abrasion is necessary.

The clinical signs are characterized by hair loss (alopecia), and focal dull yellow crusts on the muzzle, head, ears, face, tail, and extremities. The crusts are composed of skin debris, and fungal elements. Hair invasion has not been observed in mice. The lesions are similar in other species including humans.

For any person suspected of having dermatomycosis, they should see their physician for appropriate diagnosis and treatment.

In mice or humans, the diagnosis is often made by the clinical signs. However, the diagnosis can be confirmed easily by making a cytology slide from one of the lesions and staining the slide with a fungal stain or periodic acid-Shiff stain. Trichophyton can readily be grown on Sabaroud’s agar.

Some species of dermatophyte will appear apple-green when examined by ultraviolet light (UV). My ~16 year-old cat had “ringworm” when she was a kitten and the crusts appeared apple-green under UV light. I also became infected where she had accidently scratched me on my arm.

In severe cases, oral antifungal medication may be indicated. For mild cases, topical therapy is usually sufficient. In rodents, it is important to make sure that the animals do not concurrently have mites. Mites are very pruritic (itchy) and the skin abrasions caused by scratching would be highly susceptible for infection by the high level of fungal spores present in an animal with an active infection. Although fungi are ubiquitous in the environment, the level of spores is high in infected animals. In this case, good husbandry techniques are recommended when handling infected animals or cleaning the cages. *

Updated April 9, 2014