What is a common louse? - briefly
A common louse is a tiny, wingless ectoparasite that feeds on human blood and resides in scalp or body hair. It belongs to the species Pediculus humanus, encompassing both head and body lice.
What is a common louse? - in detail
The common human louse is an obligate ectoparasite that feeds exclusively on blood from the scalp or body surface of its host. It belongs to the order Phthiraptera, family Pediculidae, and the species most frequently encountered is Pediculus humanus capitis for head infestations and Pediculus humanus corporis for body (clothing) infestations.
Adult lice measure 2–4 mm in length, have a dorsally flattened body, six legs with clawed tarsi for grasping hair shafts, and lack wings. Their mandibles are adapted for piercing skin and sucking blood. Color varies from pale gray to brown, darkening after a blood meal.
The life cycle comprises three stages: egg (nit), nymph, and adult. Eggs are cemented to hair shafts near the scalp and hatch in 7–10 days. Nymphs undergo three molts over 9–12 days before reaching maturity. An adult lives for 30–40 days, during which a female produces 5–10 eggs per day.
Infestation symptoms include itching caused by an allergic reaction to saliva, visible nits attached to hair, and the presence of live lice. Heavy loads may lead to secondary bacterial infections from scratching.
Control measures rely on mechanical removal and chemical treatment:
- Mechanical: Wet combing with a fine-toothed louse comb, repeated every 2–3 days for two weeks.
- Chemical: Topical pediculicides (permethrin 1 %, pyrethrins with piperonyl‑butoxide, dimethicone) applied according to label instructions. Resistance to pyrethroids has been documented; alternative agents should be considered when treatment fails.
- Environmental: Washing bedding and clothing in hot water (≥ 60 °C) or sealing items in plastic bags for two weeks to kill surviving stages.
Prevention emphasizes regular head inspection, especially in school settings, and avoidance of sharing personal items such as combs, hats, or headphones. Early detection and prompt treatment interrupt transmission cycles and limit outbreaks.