ringworm in pets

Ringworm In Pets | cat at vet looking at ringworm
Posted by Dr. Nina Mantione on Aug 07 2012

Summertime is the height of kitten season, making it one of my favorite times to be a vet. But one thing I see a lot of this time of year is patchy kittens – not the calico multicolored kind (although there are a number of those in the bunch), but kitties who are scruffy and missing clumps of fur.

The first thought that enters my mind when one of these little guys tumbles onto my exam table is – ringworm! Actually, ringworm is not a worm. The term is a misnomer and refers to rash that this fungal infection causes in humans. That’s right, ringworm is another zoonotic disease, meaning two-leggers can catch it from pets.

What is ringworm?

Ringworm, or dermatophytosis, is actually a contagious fungal infection that is very common in cats. It occurs in dogs, but not quite as frequently. Ringworm is very contagious and can easily contaminate the environment that the pet lives in – getting into carpets, furniture, and air vents. For this reason, it should be diagnosed and treated as quickly as possible.

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While pets experience patchy hair loss, in people, ringworm typically causes a small, itchy circular rash with a clear center – the “ring.” It tends to occur on the areas that have been in direct contact with an infected pet, so our necks, faces, and forearms are common locations.


For accurate diagnosis and effective treatment of ringworm, a trip to your veterinarian is definitely in order. The diagnosis is made based on the history, clinical signs, and a few diagnostics tests. I always ask if any humans in the household have a rash too. The first quick diagnostic test I run is the use of a Wood’s lamp. When seen under a Wood’s lamp, which is essentially a black light, ringworm infections give off a green glow along the infected hair shafts. If this test is positive, my diagnosis is made!

If the Wood’ lamp is negative, I move onto the fungal culture, which is a test I can run in my office. Fungal cultures can take up to three weeks to turn positive, so I won’t always have the diagnosis right away.


Treating ringworm depends on the severity of the lesions and the number of pets in the household. In the very mild cases, topical antifungals and bathing animals with antifungal shampoo may do the trick. Severely infected animals require the same topical treatments, plus a long course of oral medications.

I always remind pet owners that their environment needs to be disinfected. When we have a situation where a shelter or home with many infected pets, the entire premises may need to be cleaned, including the air ducts, in order to fully eradicate the infection.

If you suspect your pet has ringworm, bring him to see the vet immediately, to ensure your whole family stays healthy!

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