Of the 200 or so species of sucking lice, only three infest man: the body louse, Pediculus humanus, the head louse, P. capitis and the pubic louse, Pthirus pubis (also known as the crab louse). Only the body louse is a vector of disease. In Europe, infestations by body lice have, until recently, been uncommon for some time; head lice infestations on the other hand are extremely common, mainly among children, while infestations by pubic lice appear to be increasing to the extent that they may be considered a marker for sexually transmitted diseases. Head lice infestations are found virtually only on the hairs of the head; body lice attach to garments where they feed on the skin and attach their eggs to clothes, most frequently along the seams of clothing. Pubic lice, as indicated by their name, are generally found only in the pubic areas though many infestations of eyelids and eyebrows have been reported.

Louse-borne rickettsial diseases

Epidemic or louse-borne typhus

Epidemic typhus or louse-borne typhus due to Rickettsia prowazekii is transmitted by the human body louse, Pediculus humanus. The infective agent is transmitted from person to person through contaminated faeces of the human body louse which is the only known vector. Until World War II, the disease was periodically responsible for an enormous number of cases and a great many deaths especially among armies, refugees and inmates of camps of all types.