What are lice and where do they come from? - briefly
Lice are small, wing‑less parasitic insects that inhabit the hair or feathers of mammals and birds, feeding on blood or skin debris. They emerge from eggs deposited by adult females and are transmitted through direct contact or shared items such as clothing, combs, or bedding.
What are lice and where do they come from? - in detail
Lice are obligate ectoparasites of mammals, belonging to the order Phthiraptera. Three species commonly infest humans: Pediculus humanus capitis (head lice), Pediculus humanus corporis (body lice), and Pthirus pubis (pubic lice). All possess flattened bodies, clawed legs for gripping hair or clothing fibers, and mouthparts adapted for piercing skin and sucking blood.
The life cycle consists of egg (nit), three nymphal instars, and adult. Eggs are cemented to hair shafts or fabric and hatch in 7–10 days. Each nymph matures to adulthood in another 7–10 days, after which females lay 5–10 eggs per day for several weeks. The entire cycle can be completed in 2–3 weeks under optimal temperature (30–32 °C) and humidity.
Transmission occurs primarily through direct head‑to‑head contact for head and pubic lice, and via contaminated clothing, bedding, or personal items for body lice. Body lice thrive in environments where clothing is not changed or washed regularly, linking infestations to crowded or unhygienic conditions. Human migration, communal living, and shared grooming tools also facilitate spread.
Key reservoirs include:
- Infested individuals (the only hosts for head and pubic lice)
- Clothing and linens infested with body lice
- Crowded shelters, prisons, or refugee camps where hygiene standards are compromised
Risk factors comprise close personal contact, inadequate laundering of garments, and limited access to clean water. Infestations are more prevalent among school‑age children for head lice and among homeless populations for body lice.
Control strategies focus on:
- Mechanical removal of eggs and insects using fine‑toothed combs or manual extraction.
- Application of pediculicidal agents (e.g., permethrin, ivermectin) following label instructions.
- Laundering clothing and bedding at ≥ 60 °C or sealing items in airtight bags for two weeks to kill dormant lice and eggs.
- Treating all close contacts simultaneously to prevent reinfestation.
- Improving personal hygiene and environmental sanitation in high‑risk settings.
Understanding the biology, transmission pathways, and environmental conditions that support lice populations enables effective prevention and eradication measures.