How do lice appear and how are they transmitted? - briefly
Lice develop from eggs (nits) deposited by adult females on hair shafts; the eggs hatch into nymphs that mature into reproducing adults. Transmission occurs mainly via direct head‑to‑head contact or by sharing combs, hats, or other personal items that have touched an infested scalp.
How do lice appear and how are they transmitted? - in detail
Lice infestations begin when viable eggs, commonly called nits, are deposited on hair shafts close to the scalp. The female adult lays 6‑10 eggs per day, cementing them with a proteinaceous glue that resists removal. Eggs hatch after 7‑10 days, releasing nymphs that resemble miniature adults but lack fully developed reproductive organs. Nymphs undergo three molts over 9‑12 days, each stage lasting about 2‑3 days, before reaching sexual maturity. Adult lice live 30‑40 days on the host, feeding exclusively on blood several times daily; they die within 1‑2 days when removed from the host environment.
Transmission occurs primarily through direct, sustained head‑to‑head contact, which provides the necessary proximity for lice to crawl onto a new host. Secondary pathways include:
- Sharing personal items such as combs, brushes, hats, helmets, or hair accessories that have recent contact with an infested scalp.
- Contact with contaminated bedding, towels, or clothing, especially when these items remain moist and retain viable nymphs or eggs.
- Use of communal facilities (e.g., schools, camps, shelters) where close contact and shared objects are frequent.
Body lice, which inhabit clothing seams rather than hair, spread mainly via contaminated garments that are not regularly laundered at temperatures above 130 °F (54 °C). Pubic lice transmit through sexual contact or sharing of intimate garments and towels.
Environmental factors that favor infestation include warm, humid conditions that accelerate egg development and prolong adult survival. Regular laundering of clothing and bedding at high temperatures, combined with avoidance of head‑to‑head contact, disrupts the life cycle and prevents spread.