Pediculosis capitis (head lice infestation) (synonyms: head lice infestation, pediculosis due to Pediculus humanus capitis; ICD-10 B85.0: pediculosis due to Pediculus humanus capitis) refers to infestation of the scalp with the head louse (Pediculus humanus capitis). It belongs to the order Anoplura (lice).
Head lice are lice about two to three millimeters in size that have claw-like appendages on their legs. They use their stiletto-like extensions of the head to scratch the top layer of skin and suck up the blood. They appear whitish-greyish in populations with poor skin pigmentation and more brownish in populations with darker skin. After sucking blood, the louse appears reddish. The head lice belong to the ectoparasites that are parasites that live on the surface of the body.
Pediculosis capitis is the most common childhood parasitosis in Germany and the second most common contagious disease after the common cold.
Humans currently represent the only relevant pathogen reservoir.
Occurrence: The infection occurs worldwide.
The disease occurs throughout the year. Small epidemics of head lice in a family, kindergarten or school class are typical.
Transmission of the pathogen (infection route) occurs through direct hair-to-hair contact. Note: Shared headgear and bedding do not play a role in transmission.
In case of initial infection (first infestation with the parasite), symptoms appear on the scalp after 4-6 weeks; in case of reinfestation after 24-48 hours.
Sex ratio: girls are affected significantly more often than boys; males and females are equally affected.
Peak incidence: The peak incidence of head louse infestation is in childhood, due to attendance at communal facilities.
Course and prognosis: The course of head louse infestation depends on how quickly topical therapy is started. In order to capture all larvae, the therapy with the “lice remedy” must be repeated after 7 to 10 days according to the usual recommendations so far. This recommendation has to be revised, because in a study it could be proven that even 13 days after the local treatment or later, live lice were still found on the head of the patients, although the treatments had been repeated after 7 to 10 days as recommended. Therefore, a third local treatment is recommended to kill the last hatched lice before the female lice start laying eggs again.
According to the Infection Protection Act, parents must inform the school or kindergarten of a head lice infestation in their children.
