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Ringworm (feline dermatophytosis) is one of the most common skin disorders affecting the feline population worldwide. Despite its name, it is a fungal infection that has nothing to do with worms. and the only thing to do with the rings is the circular area of itchy rash that will normally, but not necessarily, appear on the skin of an infected animal.
The fungi responsible for the condition are called dermatophytes, microscopic organisms that originate in soil but can thrive as parasites beyond their home environment. Once entrenched in the host’s body, the fungi thrive by digesting keratin, a protein substance that is the main structural component of hair and nails. As the keratin is consumed, the microscopically small fungi reproduce rapidly, creating millions of single-celled reproductive bodies (spores) that are capable of developing into new microorganisms.
When dermatophytes come into contact with healthy feline tissue, several different phenomena can occur: they can be brushed by a meticulously grooming cat; they may lose out in competition with more robust microorganisms and eventually disappear; they can take up residence on the skin without causing any adverse reaction; or, in the worst case, they can settle en masse on the animal’s skin and cause dermatitis, an inflammatory disease that can manifest itself in a variety of unpleasant ways.
If left untreated, says William Miller Jr., professor of dermatology at Cornell University’s School of Veterinary Medicine, ringworm in an otherwise healthy cat will likely resolve on its own over time. however, he points out, “feline ringworm is not something you want to take lightly. if it disappears without treatment, the process usually takes between nine months and a year, during which time the animal’s hair will continue to fall and its bare skin will be exposed. this can increase the risk of the animal suffering from skin breaks and subsequent infection.”
Also, he points out, ringworm is a zoonotic disease: it can be transmitted from an infected cat to a human who comes into contact with it. therefore, the condition can pose a significant threat to both people and cats.
the clearest and most common clinical signs of feline ringworm include: circular areas of hair loss, broken hair and no beard, scaly or crusted skin, changes in hair or skin color, inflamed areas excessive brushing and scratching, infected claws or nail beds, and dandruff.
If ringworm is suspected, a veterinarian will first try to exclude the presence of other skin conditions that the infection may resemble, such as flea allergies. toward this goal, says dr. miller, the vet can examine the cat’s fur with a wood lamp, an ultraviolet light under which fungus-covered fur will glow a yellowish-green. hairs that fluoresce in this way are examined microscopically for specific spores and other fungal characteristics.
If ringworm is diagnosed, treatment will usually involve applying topical antifungal medications to all infected areas and, in most cases, a systemic medication as well. if lesions are present on many areas of a cat’s skin, a full body rinse or bath may be used. It will take at least six weeks of repeated treatments to completely cure a feline ringworm infection, he notes, “and perhaps much longer in some cases.”
