Head Lice: An Under-Recognized Tropical Problem


Head lice, caused by infestation with Pediculus humanus capitis, is an extremely common problem in tropical countries. Pediculus humanus capitis is an obligate human ectoparasite. Morphologically, head lice are indistinguishable from Pediculus humanus corporis, the human body louse, although they are slightly smaller. Unlike body lice, head lice have not clearly been proven to be vectors for infectious agents. Adult head lice develop through three nymphal stages (Figure 1) and feed on blood from the scalp two to six times a day causing discomfort and pruritus. On examination, the eggs (nits) are more commonly identified than adult lice (Figure 2). The complete life cycle takes 15-20 days, and adults survive up to 1 month. Adults mate once, and a fertilized female then produces 3 to 4 eggs per day (Figure 3) for the remainder of their lives. Nymphs must feed immediately on hatching, and therefore, nits located …

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