The head louse, Pediculus capitis, infests 10-12 million people each year in the United States. Pediculosis or “lousiness” is one of the most prevalent communicable conditions in this country. Lice are primarily transferred from person to person by direct head-to-head contact or by several people using the same combs, brushes, hats, costumes, athletic equipment, towels, or bedding. Head lice are not found on animals or household pets and are not transmitted from pets to humans. Because of children’s play activity and close contact, head louse infestations are usually found on children, but can also be spread to adults. The head louse is not considered to be a serious vector of disease in the United States although severe infestations may cause irritation, scratching, and subsequent invasion of secondary infection from germs and lice feces. Itching from large numbers of bites may make the infested individual feel tired, irritable, and feverish, thus the term “feeling lousy”.
Lice have three pairs of legs which makes them true insects. Lice do not have wings or powerful jumping legs so they move about by clinging to hairs with claw-like legs.
The eggs of lice are called nits. They are oval white cylinders (1/16 inch long). The eggs of head lice are glued to hairs of the head near the scalp. To protect the eggs from extremes in light and temperature, the female will commonly glue the eggs behind the ears and along the nape of the neck. Under normal conditions, the eggs will hatch in 7-10 days. The young lice which escape from the egg must feed within a few hours or they will die. Newly hatched lice will periodically take blood meals and molt three times before becoming sexually mature adults. A young louse will develop in 10-12 days to an adult (1/8 inch in length). Depending on climate and color of the host’s hair, adult lice range in color from white to brown to dark gray.
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