What types of lice are there? - briefly
The main human lice are head lice (Pediculus capitis), body lice (Pediculus humanus corpus), and pubic lice (Pthirus pubis). Other lice species parasitize mammals, birds, and various animals, each specialized for the host’s hair or feathers.
What types of lice are there? - in detail
Lice are obligate ectoparasites that belong to the order Phthiraptera. Three species infest humans, each adapted to a specific region of the body and exhibiting distinct morphology and behavior.
The head‑infesting species, Pediculus humanus capitis, measures 2–4 mm, has a rounded body, and clings to hair shafts with clawed legs. It spreads primarily through direct head‑to‑head contact and, less frequently, via shared combs or hats. Eggs (nits) are attached to the hair shaft near the scalp, and the nymphal stages develop over 7–10 days before reaching adulthood.
The body‑infesting form, Pediculus humanus corporis, is slightly larger, 3–5 mm, and prefers clothing seams for shelter. It moves to the skin only to feed, laying eggs on fabric fibers. Transmission occurs through contaminated clothing, bedding, or close personal contact, especially in crowded or unhygienic settings. The life cycle mirrors that of the head louse but may extend to 12 days due to cooler environments.
The pubic or crab louse, Pthirus pubis, is 1.5–2 mm long, with a broad, crab‑shaped body and robust claws that grasp coarse hair. It inhabits the genital region, perianal area, and occasionally facial hair. Transmission is mainly sexual, though sharing towels or clothing can also spread the parasite. Eggs are attached close to the skin surface, and development completes in about 10 days.
Less common lice affect non‑human hosts but occasionally bite humans. These include:
- Rodent lice (Polyplax spp.) – infest mice and rats; can transmit pathogens to humans handling infested rodents.
- Bird lice (Menacanthus, Philopterus spp.) – live on feathers; human contact occurs in poultry farms or pet bird care.
- Cattle and sheep lice (Bovicola, Linognathus spp.) – primarily veterinary concerns, but occupational exposure can cause transient infestations.
All lice undergo a hemimetabolous development: egg → three nymphal instars → adult. Feeding involves piercing the host’s skin and ingesting blood, which can cause irritation, secondary infection, and, in severe cases, anemia. Effective control requires mechanical removal of nits, topical insecticides approved for the specific species, and hygiene measures to eliminate fomites for body lice.