What is a louse and how is it treated? - briefly
A louse is a tiny, wingless ectoparasite that feeds on human blood and inhabits hair or clothing. Effective treatment involves applying a pediculicide (e.g., permethrin or ivermectin) and meticulously combing out nits with a fine-tooth comb.
What is a louse and how is it treated? - in detail
Lice are obligate ectoparasites belonging to the order Phthiraptera. Three species commonly affect humans: Pediculus humanus capitis (head louse), Pediculus humanus corporis (body louse), and Pthirus pubis (pubic louse). Adult insects measure 2–4 mm, possess clawed legs adapted for gripping hair shafts, and feed exclusively on blood. Their life cycle comprises egg (nit), nymph, and adult stages; development from egg to adult requires 7–10 days under optimal temperature and humidity. Eggs are cemented to hair shafts and hatch after 7–10 days; nymphs undergo three molts before reaching maturity.
Infestation manifests as itching, irritation, and secondary bacterial infection from scratching. Diagnosis relies on visual identification of live lice or viable nits within 1 cm of the scalp. Nits attached firmly to the hair shaft and close to the scalp indicate active infestation, whereas detached or older nits may be residual.
Effective management combines chemical, mechanical, and environmental measures:
- Topical pediculicides: Permethrin 1 % lotion, pyrethrin‑based products, and malathion 0.5 % are applied to dry hair, left for the recommended duration, then rinsed. Resistance to pyrethroids is documented; confirm product efficacy before use.
- Mechanical removal: Fine‑toothed nit combs, used on wet hair with conditioner, remove live insects and eggs. Repetition every 2–3 days for two weeks eliminates residual stages.
- Oral agents: Ivermectin 200 µg/kg single dose, repeated after 7 days, treats resistant cases. Spinosad oral formulation is an alternative for pediatric patients.
- Environmental control: Wash bedding, clothing, and personal items in hot water (≥60 °C) or seal in airtight bags for 2 weeks. Non‑washable items may be frozen at –20 °C for 48 hours.
Follow‑up examination 7–10 days after initial treatment confirms eradication; persistent lice require a second line of therapy, often a different class of pediculicide or combined oral and topical regimen. Education on avoiding head-to-head contact and regular inspection of hair in close‑contact settings reduces recurrence.