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Phthirus pubis

Common name. pubic louse, crab louse

Disease. phthiriasis, pediculosis pubis

Life cycle. Almost exclusively a parasite of man. Infestation is usually through sexual intercourse, but it can arise from infested clothing or bedding. P. pubis dwell primarily in the pubic region, but it may also be found in the axilla, beard, mustache, eyebrows, eyelashes, and chest. The life cycle, from egg laying to formation of the adult, is about 17-25 days. The female lay about 30 eggs during her life. The eggs (nits) are cemented to hair, and hatch within 6 to 8 days. The nymph undergoes three molts within two weeks. The life span of the adult is about 1 month.

Morphology. The lice are 1.5-2.0 mm in length and nearly as broad as long. The adult has a crab-shaped body, a rectangular head, and three pairs of legs. The front pair of leg is much more slender and has smaller claws than the other two pairs. The characteristic large claws are located on the middle and hind-legs.

Pathology and clinical symptoms. There may be either no symptoms, or there may be itch due to allergic reactions to the injected saliva. The skin may become thickened and shows spots of hyperpigmentation in the chronic case.

Diagnosis. Definitive diagnosis can be made easily with naked eyes by finding the adult or eggs.

Prevention. Close contact or sexual intercourse with infected person should be avoided.

Comments. Current sexual partners should be examined and treated also.

Yun-Kyu Park

Pubic louse(Phthirus pubis) female (dorsal view of slide-mounted specimen), belonging to Phthiridae, Anoplura.

Tai Soon Yong

Phthirus pubis.

Sung-Jong Hong