Phthirus pubis has a ectoparasitic relationship with humans (Mimouni, et al. 2002)  The crab louse most commonly infests the pubic hair due to the proper spacing conditions it provides.  Crab louse may also be located on abdomen and thigh hairs, and occasionally axillary hairs and eyelashes of children.  After a human host is found, Phthirus pubis anchors its mouthpiece to the skin of its human host to suck blood at frequent intervals.  It feeds virtually at all times, which may explain its short lifespan when it is not attached to its human host.  When the crab louse is not attached to its host its lifespan is less than 20 hours; however, its lifespan increases to about a month when on its human host (Fisher and Morton 1970).  This parasitic crab louse causes discomfort to its host via burning or itching (Puri, et al. 2009).


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