"Louse" - what is it, definition of the term
“Louse” denotes a small, wingless, obligate ectoparasite of mammals and birds, classified in the order Phthiraptera; it feeds on blood or skin debris, possesses a flattened body adapted for movement through hair or feathers, deposits eggs (nits) directly on the host, and can serve as a vector for pathogenic microorganisms.
Detailed information
The parasitic insect Pediculus species, commonly referred to as head and body lice, belongs to the order Phthiraptera. It is a wingless ectoparasite adapted to human hosts, exhibiting a flattened body that facilitates movement through hair shafts and clothing fibers.
Morphologically, the adult measures 2–4 mm in length, possesses six legs with clawed tarsi, and lacks functional wings. The head is equipped with sensory palps, while the abdomen contains a simple digestive tract and reproductive organs. Color varies from pale to dark brown, reflecting recent blood meals.
The developmental cycle comprises three stages: egg (nit), nymph, and adult. Eggs are cemented to hair shafts for 7–10 days before hatching. Nymphs undergo three molts over 9–12 days, reaching maturity in approximately two weeks. Under optimal conditions, a single female can produce up to 30 eggs per day, leading to rapid population expansion.
Host specificity is high; humans serve as the primary reservoir. Transmission occurs through direct head-to-head contact or via contaminated personal items such as combs, hats, and bedding. Body-dwelling forms may spread through shared clothing or linens. Infestation prevalence peaks in crowded or low‑hygiene environments.
Medical consequences include pruritic lesions from repeated biting, secondary bacterial infection, and, in severe cases, anemia due to chronic blood loss. Body-dwelling variants can transmit pathogens such as Rickettsia prowazekii (epidemic typhus) and Bartonella quintana (trench fever).
Control strategies focus on eradication of the parasite and prevention of reinfestation:
- Apply a topical insecticide (e.g., permethrin 1 %) to the scalp or body surface, following label instructions.
- Remove viable eggs with a fine‑toothed comb, repeating the process every 2–3 days for two weeks.
- Wash clothing, bedding, and personal items in hot water (> 60 °C) and dry on high heat for at least 30 minutes.
- Vacuum carpets and upholstered furniture to eliminate fallen nits.
- Educate affected individuals about avoiding head‑to‑head contact and maintaining personal hygiene.
These measures, when implemented consistently, reduce infestation rates and limit disease transmission associated with the parasite.