Pediculus

Pediculus is a genus of parasitic lice in the family Pediculidae, order Phthiraptera. Members are obligate ectoparasites that feed on the blood of mammals. The best known species affecting humans is Pediculus humanus, which comprises two subspecies: Pediculus humanus capitis (head louse) and Pediculus humanus humanus (body louse). A related louse on other primates is also classified within this genus.

Physical description and life cycle: Pediculus species are small, wingless, dorsoventrally flattened insects about 2–3 mm long. They attach to hair and skin using strong claws, and lay eggs (nits) glued to hair shafts close to the scalp. Females lay numerous eggs that hatch after about 6–9 days into nymphs, which molt three times before becoming adults. Adults typically live on the host for about 2–4 weeks, feeding daily on blood.

Transmission and ecology: Head lice spread mainly through direct head-to-head contact, particularly among children. Body lice are transmitted through shared clothing or bedding and are associated with crowded or unsanitary conditions. Both forms are more prevalent in areas with close person-to-person contact.

Medical importance: Head lice cause itching and discomfort but are not typically disease vectors. Body lice historically served as vectors for diseases such as epidemic typhus, relapsing fever, and trench fever, though such transmissions are less common in modern settings.

Diagnosis and treatment: Diagnosis is usually by visual inspection or fine-tooth combing to detect lice or nits. Treatments include topical pediculicides (for example, permethrin or malathion) and thorough combing. Environmental decontamination involves washing clothing and bed linens and cleaning personal items; resistance to some treatments can occur, sometimes requiring alternative medications or repeated dosing.

Etymology and taxonomy: The name Pediculus derives from Latin for “little louse.” Taxonomically, Pediculus is a genus within Phthiraptera, the sucking lice.