Pediculosis
Pediculosis is caused by parasitic forms of lice: Pediculus humanus var. capitis causes pediculosis capitis (head lice), Pediculus humanus var. corporis causes pediculosis corporis (body lice), and Phthirus pubis causes pediculosis pubis
(crab lice). These lice feed on human blood and lay their eggs (nits) in body hairs or clothing fibers.
(crab lice). These lice feed on human blood and lay their eggs (nits) in body hairs or clothing fibers.
After the nits hatch, the lice must feed within 24 hours or die; they mature in 2 to 3 weeks. When a louse bites, it injects a toxin into the skin that produces mild irritation and a purpuric spot. Repeated bites cause sensitization to the toxin, leading to more serious inflammation. Treatment can effectively eliminate lice.
Causes
P. humanus var. capitis (the most common species) feeds on the scalp and, rarely, in the eyebrows, eyelashes, and beard. This form of pediculosis is caused by overcrowded conditions and poor personal hygiene and commonly affects children, especially girls. It spreads through shared clothing, hats, combs, and hairbrushes.
P. humanus var. corporis lives in the seams of clothing, next to the skin, leaving only to feed on blood. Common causes of this type of pediculosis include prolonged wearing of the same clothing (which might occur in cold climates), overcrowding, and poor personal hygiene. It spreads through shared clothing and bedsheets.
P. pubis is primarily found in pubic hairs, but this species may extend to the eyebrows, eyelashes, and axillary or body hair. Pediculosis pubis is transmitted through sexual intercourse or by contact with clothes, bedsheets, or towels harboring lice.
Signs and symptoms
Clinical features vary with the cause.
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