How do pubic lice differ from head lice? - briefly
Pubic lice (Pthirus pubis) are broader, crab‑shaped insects that cling to coarse hair of the genital region and are primarily transmitted through sexual contact, whereas head lice (Pediculus humanus capitis) are smaller, elongated parasites that inhabit scalp hair and spread by direct head‑to‑head contact. The species differ in morphology, preferred habitat, and typical transmission routes.
How do pubic lice differ from head lice? - in detail
Pubic lice (Pthirus pubis) and head lice (Pediculus humanus capitis) are distinct ectoparasites that infest humans. Both belong to the order Phthiraptera, yet they differ markedly in anatomy, preferred habitat, transmission, life cycle, clinical manifestations, and management.
Morphology
- Size: pubic lice measure 1–2 mm; head lice are slightly larger, 2–4 mm.
- Body shape: pubic lice have a broader, crab‑like abdomen; head lice possess a more elongated form.
- Legs: pubic lice bear short, stout legs with clawed tarsi adapted for grasping coarse hair; head lice have longer legs with finer claws suited for fine scalp hair.
- Color: pubic lice appear gray‑brown; head lice range from light to dark brown, often changing after a blood meal.
Habitat and host preference
- Pubic lice colonize the pubic region, perianal area, and occasionally coarse body hair such as axillary, facial, or chest hair.
- Head lice reside exclusively on the scalp, attaching to hair shafts near the scalp surface.
Transmission pathways
- Pubic lice spread primarily through intimate sexual contact; secondary routes include sharing towels, clothing, or bedding.
- Head lice transmit via prolonged head‑to‑head contact; sharing combs, hats, or pillows also facilitates spread.
Life cycle characteristics
- Egg (nit) attachment: pubic lice deposit nits on coarse hair shafts close to the skin; head lice attach nits to the side of scalp hairs.
- Incubation: pubic lice eggs hatch in 6–10 days; head lice eggs hatch in 7–10 days.
- Development: both progress through three nymphal stages, reaching adulthood in approximately 2–3 weeks. Adult lifespan averages 30 days for pubic lice and 30 days for head lice under optimal conditions.
Symptoms and clinical presentation
- Itching: pubic lice cause intense pruritus in the genital area, often intensified after bathing; head lice produce scalp itching, typically worsening 4–6 weeks after infestation.
- Lesions: pubic lice may generate small erythematous papules and excoriations; head lice can cause superficial scalp irritation, crusting, and occasional secondary bacterial infection.
- Visibility: pubic lice and their nits are observable on coarse hair; head lice and nits are seen on scalp hair, especially behind the ears and at the nape.
Management strategies
- Pubic lice: topical pediculicides (permethrin 1 % cream rinse, pyrethrins with piperonyl butoxide), oral ivermectin, and thorough washing of clothing and bedding at ≥ 60 °C.
- Head lice: over‑the‑counter shampoos containing dimethicone, permethrin 1 % lotion, or malathion 0.5 %; manual removal of nits with fine‑toothed combs; repeated treatment after 7–10 days to target newly hatched lice.
- Environmental control: laundering infested items, vacuuming furniture, and avoiding sharing personal items reduce reinfestation risk.
These distinctions guide accurate diagnosis and appropriate therapeutic interventions for each ectoparasitic infestation.