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Ringworm in cats

August 3, 2020

Ringworm in cats
Patient: Daisy

This is Daisy. She came for a visit to the clinic for hair loss on her nose that was a bit itchy. Daisy’s nose was examined by the vet and then tested under a UV light (woods lamp) for ringworm. A positive ringworm test occurs when the hair follicles turn a bright yellow/apple green colour under the woods lamp. As you can see by the photos, Daisy’s ringworm test was positive.
Ringworm (despite its name) is not caused by a worm. It is caused by a fungus/dermatophyte called Microsporum canis (M canis). The dermatophyte grows in the hair and in the skin, using the superficial layers of the skin for nutrition. The infection is contagious to humans and causes characteristic skin lesions in young children and immunocompromised adults.
The appearance of ringworm can be quite varied. It can cause discrete areas of hair loss that may appear inflamed and scaly, to more severe skin disease.
It is diagnosed by an examination under UV (woods lamp) light. Only 50% of cases of M. canis will show fluorescence with the woodslamp, for this reason, your vet may do a fungal culture to diagnose the suspected infection.
Treatment is always advised because of the zoonotic risk to humans and the risk of infection spread to other animals in the household. Treatment often involves an antifungal tablet and a topical antifungal cream / shampoo.
Preventing spread to humans and other animals can be achieved by decontamination of the environment. This involves physical removal of infected hairs by regular vacuuming and chemical disinfection to kill the fungal spores. All areas should be cleaned as thoroughly as possible and ideally vacuum bags should be burned as this will destroy the spores. Disinfectants effective against dermatophyte spores are those containing hypochlorite or gluteraldehyde solutions.

If you or any of your family members have suspected ringworm lesions, please contact your GP for an appointment.