I recently adopted a kitten and shortly afterwards she developed patchy areas on her coat which I am told could be ringworm. Is this contagious to humans?

“Ringworm” is the common name given to a fungal infection of the superficial layers of the skin, hairs and nails. The name comes from the classical appearance of C-shaped red raised ‘ring’ marking the boundary of inflammatory lesions of the infection in people. The fungi responsible for ringworm belong to a specialized group known as dermatophytes, and these can cause disease in both humans and animals. In cats, one type (species) of dermatophyte called Microsporum canis is responsible for almost all ringworm infections, and this species is infectious to both cats and dogs, and also man.

The lesions of ringworm in cats may be very mild or even undetected. A ‘cigarette ash’ scaling in the depths of the coat may be the only visible indicator.

In other cases there are discrete, circular, thickened plaques with hair loss (alopecia) that occurs due to the increased fragility of infected hairs. The main sites for these lesions are the skin of the head, chest, forelegs and along the ridge of the back to the base of the tail. These lesions are not usually itchy.

Occasionally infection of the claws (onychomycosis) may occur. Claws become rough and pitted with a scaly base. The claw may become deformed. Ringworm may sometimes cause a more generalized disease where a much larger area of the body is affected often with patchy hair loss.

Confirmation of ringworm requires culture of the fungus in a laboratory. For this a sample of hair and skin scrapings are taken. Culture results take up to four weeks but there is usually an indication within a few days if the result is positive.

Because there are a number of causes of hair loss in cats these other causes may have to be ruled out by additional tests.

Two forms of treatment can be used for cats with ringworm - topical therapy (application of creams, ointments or shampoos) and systemic therapy (administration of anti-fungal drugs by mouth). In addition, attention must also be given to cleaning the environment.

The vast majority of cats, if treated appropriately, will recover from ringworm infection within a few weeks. While the appearance of the lesions may not change much during the first week or so of treatment, some improvement should be evident within 2-3 weeks. Occasionally, despite appropriate treatment, the infection persists, and in this situation your veterinarian may have to try alternative anti-fungal drugs.

Ringworm can be transmitted quite readily to humans (particularly children) and it is important to take appropriate steps to minimize exposure to the fungus while the cat is being treated.

If any humans in the house develop skin lesions (small patches of skin thickening and reddening, typically sharply demarcated with raised scaly edges) early medical attention should be sought. Ringworm in humans generally responds very well to treatment.