Categories: ringworm

How do cats spread ringworm?

Ringworm (dermatophytosis) is spread by cats in direct contact with each other or with materials that have been contaminated with the skin debris of an infected cat or another animal or indeed a human. Ringworm is zoonotic, which means it can be transmitted between animals and humans. This does not only mean that animals can give it to people, it also means that people can give it to animals. I wonder how many cat owners have given their cats an infection of ringworm without realising it.

Cat with ringworm. Picture in public domain.

The most common species of dermatophytosis which infects cats is Mircosporum canis (M canis). It is the same organism that causes ringworm in dogs. It is believed that the main source of ringworm infections in humans is from their domestic cat companions.

I, myself, have ringworm which I get rid of through UVB light when it shows as a symptom on a small area of either of my legs (2 x approx. 30 second treatments over 2 days – see below). It’s stays away most of the time and is rarely a visible symptom. I have had it for many years. It doesn’t bother me particularly but I got it from a black cat that I lived with. I adopted him from my mother after she passed away as he lived with her.

Ringworm on person’s arm

Photo and words: Michael Broad

Warm, humid conditions, poor sanitation and crowded living areas help to promote ringworm infections. Infection rates are at their highest among kittens younger than three months of age raised at shelters or in a crowded environment.

Spores of M. canis can survive in the environment for more than 12 months. I think that needs to be spelled-out. If a cat in a household has ringworm and they deposit the fungus cells on bedding then it will be present on that bedding for 12 months or more. This may help account for its persistence.

Aasha when she first arrived at In-Sync with exceptionally bad ringworm. Photo: In-Sync Exotics.

One problem is that many cats that have the fungus on their skin never develop symptoms or they develop them months after exposure to the fungus. But the tiger above certainly did through huge neglect. The circular areas of inflammation on the skin (lesions) are caused by the toxic byproducts of the fungus which are parasites of keratin, a major structural protein inherent skin. Inflammation can also be caused by an allergic reaction of the cat. Lesions are normally first seen around the cat’s head, for limbs and/or eyes. In cats the shape of the lesion is not always well defined and circular. In fact it can be quite hard to see what it is. It only seems to be in humans where you see this well-defined circular inflammation of the skin. UV-A light detects it.

Ringworm glows under UV-A light

I’m not going to say much more about ringworm because that would be a matter for veterinarian to discuss with you. It is common and it is a problem in animal shelters. It is hard to get rid of but cats who have it should be quarantined as soon as possible from other cats and they should be carefully handled by their caretakers to avoid transmission to them. All bedding should be washed with a disinfectant solution. Infected skin scales should be vacuumed to remove them from the environment. An effective topical agent for ringworm in dogs and cats is the drug clotrimazole. Like I said, I will leave the rest to a veterinarian.

Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in a many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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