Ringworm Tests for Cats

Contrary to its name, ringworm has nothing to do with worms but is a fungal infection that grows in the superficial or dead layers of the skin, hair or nails. In affected animals, ringworm causes roughly circular areas of hair loss mainly on the head, ears or paws. Infected skin looks scaly and may also be inflamed while hairs around the infected areas appear to be broken. Veterinarians and laboratory professionals have several options available to them when diagnosing ringworm.

  1. Ultraviolet Wood's Lamp

    • As a preliminary test, an ultraviolet Wood's lamp is shone on the cat's coat in a dark room. If the cat has ringworm, the fur will fluoresce apple-green. The results of this test are not definitive, however, they can help to determine if further examination of the fur is required.

    Microscopic Examination

    • An examination of cat fur under a microscope may provide evidence of fungal elements and spores associated with ringworm. A negative result, however, it not reliable as it could simply indicate that the tested sample was not infected. It should be noted that many veterinarians choose not to use this diagnostic tool because spores are difficult to see.

    Fungal Culture

    • The most reliable method of testing a cat for ringworm is via a fungal culture. Hairs are collected from the cat, placed in a special culture medium and then incubated in laboratory in an attempt to grow ringworm fungi. If the tested hairs are infected, a positive culture will show within 10 days.

    Biopsy

    • It may sometimes be necessary to remove a skin sample from a cat for microscopic review. Fungal spores on these samples are clearly visible and a diagnosis of ringworm is reliable.