Occurrence, morphology, and biology. The crab louse occurs with some regularity in central Europe. Infestations are more frequent in adults than in children and in men more frequently than in women. This louse species can be readily differentiated from the head or body louse: small, length 1.3-1.6 mm, with trapezoid or crablike body form (Fig. 11.1d). The parasites are most often found on hair of the pubic and perianal region, more rarely on hairy areas of the abdominal region, hairs around the nipples, beard hairs, eyelashes, and eyebrows. The life cycle takes three to four weeks. Deprived of a host, crab lice die at room temperature within two days.
Epidemiology. Transmission of crab lice is almost solely by way of close body contact (sexual intercourse in adults or parent-child contact). Indirect transmission on commonly used beds, clothes, etc. is possible, but is not a major factor.
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