What are lice and what do they do? - briefly
Lice are tiny, wingless parasitic insects that inhabit the hair, scalp, or feathers of mammals and birds, feeding on blood or skin debris. Their feeding activity provokes itching, irritation, and can facilitate the spread of disease.
What are lice and what do they do? - in detail
Lice are obligate ectoparasites that live on the skin, hair, or feathers of mammals and birds. They belong to the order Phthiraptera and are wingless insects with three distinct morphological groups: head lice (Pediculus humanus capitis), body lice (Pediculus humanus corporis), and pubic lice (Pthirus pubis). Each group has adaptations for clinging to specific host regions, such as clawed legs that grasp hair shafts or feathers.
The life cycle consists of three stages: egg (nit), nymph, and adult. Females embed eggs within the host’s hair or feathers; incubation lasts 6–10 days depending on temperature. Nymphs emerge, undergo three molts over 7–12 days, and reach reproductive maturity. Adults survive up to 30 days on a host, feeding several times daily on blood. Between meals they remain motionless, attached by their claws.
Feeding behavior involves piercing the epidermis with specialized mouthparts to ingest blood. This activity can cause itching, inflammation, and secondary bacterial infection when the host scratches. In heavy infestations, blood loss may become significant, especially in vulnerable populations such as children, the elderly, or individuals with compromised immunity.
Transmission occurs through direct contact with an infested host or indirect contact via personal items (combs, clothing, bedding). Head lice spread primarily by head-to-head contact; body lice move between clothing and skin; pubic lice are transmitted mainly through sexual contact.
Control measures include:
- Mechanical removal: fine-tooth combs for head lice, careful washing of clothing and bedding at ≥60 °C for body lice.
- Chemical treatment: topical pediculicides (e.g., permethrin 1 % lotion) applied according to manufacturer instructions.
- Environmental decontamination: laundering infested fabrics, vacuuming furniture, and isolating personal items for at least two weeks.
- Monitoring: regular inspection of hair and body hair to detect reinfestation early.
Resistance to common pediculicides has been documented, prompting the use of alternative agents such as ivermectin or dimethicone formulations. Integrated approaches that combine mechanical, chemical, and environmental strategies achieve the highest success rates.