Lice are small, flightless insects that live in the hair or feathers of animals and people. Most lice are of the biting or chewing type (order Mallophaga), including the cat louse (Felicola subrostrata). Lice are most often seen on older, longhaired cats that are no longer able to groom themselves.

Lice live within the environment provided by the skin and hair. They move from host to host by direct contact. In temperate regions, lice are most common during the colder months and hard to find in the summer. Most Mallophaga lice have definite preferences as to their hosts: they will often live on only one species or several closely related species.

Lice have claws on their legs that are adapted for clinging to hair. Females glue their eggs, known as nits, to the hairs of the host near the skin. The nits are tightly attached and ordinary shampooing will not dislodge them. It takes about 3 to 4 weeks for most lice to go from nit to adult.

The first signs that your cat may have lice are scratching, biting, and rubbing of infested areas. If the lice are abundant, the hair might also be matted. Usually, diagnosis is made by seeing lice on the infested cat. Parting the hair often reveals the lice. Lice are active and can be seen moving through the hair.

Using a fine-toothed comb to dislodge nits is a tedious process that will not kill lice that have hatched. Cats and other pets are more frequently treated with dips, washes, sprays, or dusts that kill lice. Your veterinarian can recommend an appropriate control product for your pet and provide directions for its use (see Skin Disorders of Dogs: Lice of Dogs).

Lice and nits may be seen when the fur is parted.

The lice that infest cats and other pets are not normally attracted to humans. Therefore, while care in dealing with the lice infesting your pet is recommended, owners should understand that people rarely get lice from their pets.

Last full review/revision July 2011 by Karen A. Moriello, DVM, DACVD; Thomas R. Klei, PhD; David Stiller, MS, PhD; Stephen D. White, DVM, DACVD; Michael W. Dryden, DVM, PhD; Carol S. Foil, DVM, MS, DACVD; Paul Gibbs, BVSc, PhD, FRCVS; John E. Lloyd, BS, PhD; Bernard Mignon, DVM, PhD, DEVPC; Wayne Rosenkrantz, DVM, DACVD; Patricia A. Talcott, MS, DVM, PhD, DABVT; Alice Villalobos, DVM, DPNAP; Patricia D. White, DVM, MS, DACVD