Pediculus humanus and Phthirus pubis body and pubic [crab] lice

Lice are cosmopolitan parasites of humans, occurring in all areas of the world and in all socio-economic classes.  The body louse will serve as the vector for epidemic typhus (caused by Rickettsia prowazekii), trench fever (caused by Rochalimaea quintana, a rickettsia), and relapsing fever (caused by a spirochete, Borrelia recurrentis).  Severe epidemics of these diseases have occurred throughout history, particularly during wars.

Lice are spread from human to human most often by direct contact or contact with contaminated clothing, etc.  Body lice are restricted most often to the human body and head (some authorities believe the head louse is a separate species).  Crab lice are most often restricted to the pubic region, but may spread to the armpits, facial hair (beard, etc.), eyebrows, and eyelashes.  Infestations with lice are not a serious problem (as long as the lice are not infected with a disease), but they can cause a number of uncomfortable symptoms, including skin irritations and intense itching.

Pediculus humanus, the human body louse (approximate length = 2 mm).

A crab louse attached to a hair. 

A "nit" or egg of Pediculus humanus.