Ringworm is an infection of the superficial layers of the skin and of the hair fibers by one of a group of fungi, which are called dermatophytes.
How Ringworm Affects Cats
This superficial fungal infection causes few if any traumatic clinical signs in affected animals. However, it needs to be managed carefully because it is extremely contagious. When they do appear, signs of dermatophyte infection in cats include circular regions of hair loss with varying degrees of crusting and scaly skin patches. Cats are less likely to become itchy than are dogs. In some cases, affected cats develop cutaneous bumps and pustules as well. Cats also often develop military dermatitis, chin acne and generalized seborrhea in addition to the classic circular lesions. Dermatophytosis is a zoonotic condition that tends to occur in immunocompromised individuals, especially in high density populations (shelters, boarding facilities) or in patients undergoing chemotherapy, on steroid medication or suffering from poor nutrition or inordinate stress. Ringworm is ubiquitous in the environment but is more prevalent in hot, humid climates.
Causes of Feline Ringworm
In cats, most cases of ringworm are caused by Microsporum canis. Some of the fungi that cause ringworm are obligate parasites of animals; others have the same relationship with people; and some are free-living in the soil and only occasionally invade the skin of animals. All of these fungi thrive in non-living tissues – outer skin layers, hair follicles and toe nails. They are spread through direct physical contact and can also be spread through grooming tools, bedding or furniture which has come into contact with the fungi.
Preventing Ringworm Infection in Cats
The best way to prevent dermatophytosis is to prevent contact between affected and unaffected animals.
While ringworm often resolves on its own, prompt treatment can reduce the spread of infection to other pets and people and can shorten the duration of infection. Treatments for ringworm include topical and oral fungal medications. Anti-fungal drugs can cause severe side effects, especially in cats. The prognosis for cats with dermatophytosis is generally very good, except in immunocompromised individuals such as those with FIV or FeLV. However, it can take weeks to months for the fungus to be completely eliminated; long-haired cats may take over a year to clear the infection. Ringworm is highly zoonotic, and humans are at risk if exposed to an infected animal, whether or not it is showing clinical signs.