Cat lice, scientifically known as Felicola subrostratus, are small parasitic insects that live exclusively on the body of a cat. These parasites feed by chewing on skin debris and hair rather than sucking blood. An infestation is typically referred to as feline pediculosis and is most often seen in cats that are older, ill, or unable to groom themselves effectively. The primary concern for most pet owners is whether these parasites can transfer to and thrive on a human host.
Why Cat Lice Cannot Infest Humans
The impossibility of cat lice establishing a permanent population on a human is rooted in the concept of host specificity. Lice are highly specialized ectoparasites. Felicola subrostratus requires the unique physiological and environmental conditions provided by the feline host to complete its life cycle.
These cat-specific lice are classified as chewing lice, and their mouthparts are adapted for consuming the keratinous material of hair and skin flakes, not for piercing skin and drawing blood like human or sucking lice. The louse’s triangular head is specifically shaped with a groove that allows it to grasp the cylindrical hair shaft of a cat, a structure that is incompatible with the diameter and cross-sectional shape of human hair. This physical mismatch prevents the louse from moving effectively, feeding, and most importantly, cementing its eggs, or nits, to the hair shaft for reproduction.
The louse’s entire life cycle, which takes approximately three to six weeks, must occur on the host’s body. If separated from the cat, Felicola subrostratus can only survive for a short period before dying. The temperature and humidity requirements of the feline coat are specific to the parasite’s survival, making the human body an unsuitable microenvironment for a sustainable infestation. This biological limitation means that while a louse may temporarily crawl onto a human after close contact, it cannot live, feed, or reproduce, ensuring no genuine infestation will occur.
Recognizing Cat Lice
Adult cat lice are tiny, wingless insects, making them visible to the naked eye. They are yellowish to tan in color with dark markings and are dorso-ventrally flattened, allowing them to move through the dense coat.
The eggs, known as nits, are pale, translucent, and oval-shaped, cemented by the female louse to the base of the cat’s hair shafts near the skin. Unlike dandruff, which flakes off easily, nits are glued in place and are difficult to dislodge. The lice and their eggs are most commonly concentrated in areas the cat struggles to groom, such as around the head, neck, and the base of the tail. Infested cats often exhibit signs like a rough, poorly groomed coat, excessive scratching, and rubbing, which can lead to hair loss in the affected areas.
What to Do After Exposure
Although cat lice cannot infest humans, temporary transfer may occur. For humans who have been in contact with an infested cat, simple hygiene measures are sufficient to ensure no stray parasites remain.
Washing any exposed skin and hair with soap and shampoo is adequate to remove any transient lice. All bedding, clothing, and towels that have been in contact with the cat or the exposed person should be laundered using hot water and dried on a high heat setting. Vacuum carpets, furniture, and any other areas where the cat spends a significant amount of time to remove any shed eggs or adults.
A veterinarian should be consulted for proper diagnosis and to recommend an appropriate treatment plan. Treatment typically involves using veterinary-approved topical products, such as spot-ons containing active ingredients like fipronil or selamectin, which are effective against Felicola subrostratus. Since these products do not kill the nits, a second treatment is required two to three weeks later to eliminate newly hatched nymphs and break the life cycle. Treating all other cats in the household is necessary to prevent reinfestation.