What are human lice? - briefly
Human lice are small, wingless insects that live on the human body and feed on blood. The three species that affect people are the head louse, the body louse, and the pubic louse.
What are human lice? - in detail
Human lice are obligate ectoparasites that live on the skin and hair of people. Three species regularly infest humans: Pediculus humanus capitis (head louse), Pediculus humanus corporis (body louse), and Pthirus pubis (pubic louse). Each species has a distinct ecological niche, morphology, and pattern of transmission.
The adult head louse measures 2–3 mm, is wingless, and clings to hair shafts near the scalp. It feeds on blood several times a day, causing itching and potential secondary infection. The body louse inhabits clothing seams and moves to the skin to feed; it can transmit bacterial pathogens such as Rickettsia prowazekii and Borrelia recurrentis. The pubic louse, also 2–3 mm, prefers coarse hair in the genital region and feeds similarly, producing intense pruritus.
The life cycle consists of egg (nit), three nymphal stages, and adult. Eggs are cemented to hair shafts and hatch in 7–10 days. Each nymph matures into an adult after three molts over 9–12 days. Under optimal conditions, an adult female lays 5–10 eggs per day, allowing a population to expand rapidly.
Transmission occurs through direct head-to-head contact for head lice, sharing of clothing, bedding, or towels for body lice, and sexual contact or close personal contact for pubic lice. Crowded living conditions, limited access to hygiene facilities, and infrequent laundering increase infestation risk.
Clinical signs include persistent itching, visible lice or nits attached to hair shafts, and excoriated skin lesions. Diagnosis relies on visual inspection using a fine-toothed comb or magnification to locate live insects and eggs.
Effective management combines mechanical removal and chemical treatment. Wet combing with a fine-toothed comb eliminates lice and nits without insecticides. Approved topical pediculicides (e.g., permethrin 1 % or dimethicone) are applied to the scalp or affected area, following manufacturer instructions and repeating after 7–10 days to target newly hatched lice. For body lice, washing clothing and bedding at temperatures ≥ 60 °C eradicates the parasite. Pubic lice respond to the same topical agents used for head lice.
Prevention strategies include regular hair inspection, avoiding head-to-head contact in settings such as schools, maintaining personal hygiene, laundering clothing and bedding regularly, and limiting sharing of personal items. Public health measures focus on education, prompt treatment of cases, and environmental decontamination when infestations are widespread.
Epidemiologically, head lice affect millions of school-aged children worldwide, with prevalence peaks in densely populated regions. Body lice are associated with homelessness, refugee camps, and situations of poor sanitation. Pubic lice prevalence varies by age group and sexual behavior patterns. Monitoring and reporting of infestations assist health authorities in allocating resources and evaluating control programs.