Pediculosis is a dermal infestation caused by a parasitic insect (lice). Lice are sucking insects belonging to the family Pediculidae. Infestations in various body regions (e.g., head, thorax, and groin) are caused by the head louse (Pediculus humanus capitis), the body louse (Pediculus humanus corporis), and the crab louse (Phthirus pubis). There are three stages in the life cycle of the louse: the nit, the nymph, and the adult. Nits are louse eggs found firmly attached to hair shafts and take about 1 week to hatch. Nymphs mature to adults in 7 days and survive by feeding on human blood. Adult lice are about the size of a sesame seed and can live up to 30 days on an infested individual. Adult forms also feed on blood and may survive up to 2 days on inanimate objects.
Lice are transmitted by direct contact with infected individuals or common use of infected bedding, clothing, or combs, brushes, or headgear. Worldwide, as many as 6 to 12 million people are infected each year. Preschool- and elementary school-age children and their household contacts are infested most often. Prevention of occupational exposures in health care providers includes use of standard and contact precautions.
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