Dermatology, Venereology and Leprosy
Pediculosis
Pediculosis for MBBS and NEET-PG: head, body and pubic lice, nits, the crab louse, body lice as typhus vectors, permethrin and hygiene measures, mapped to NMC codes DR6.
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Pediculosis
Pediculosis for MBBS and NEET-PG: head, body and pubic lice, nits, the crab louse, body lice as typhus vectors, permethrin and hygiene measures, mapped to NMC codes DR6.
Pediculosis covers the three louse infestations that examiners contrast: head, body and pubic lice. This chapter describes their distinct organisms and habitats, the recognition of nits and the crab louse, the role of body lice as disease vectors, and treatment that ranges from permethrin to laundering clothing.
High-yield: Pediculosis
- Pediculosis is infestation by lice, with three clinical forms: head lice, body lice and pubic lice.
- Head lice are caused by Pediculus humanus capitis and are common in schoolchildren, spreading by head-to-head contact.
- The diagnosis of head lice rests on finding live lice or viable nits firmly attached to hair shafts, most often behind the ears and at the nape.
- Nits are egg cases cemented to the hair shaft and, unlike scale or dandruff, cannot be easily flicked off.
- Body lice, Pediculus humanus corporis, live and lay eggs in the seams of clothing rather than on the body and are linked to overcrowding and poor hygiene.
- Body lice are important vectors of epidemic typhus, trench fever and relapsing fever.
- Pubic lice, Phthirus pubis or the crab louse, infest coarse hair of the pubic region and are usually sexually transmitted.
- Pubic lice may also involve the eyelashes, and eyelash involvement in a child should raise concern for sexual abuse.
- Intense itching from a hypersensitivity reaction is the main symptom of all forms, often with secondary bacterial infection from scratching.
- Maculae ceruleae, bluish-grey macules, are a clue to pubic louse infestation.
- Topical permethrin is the mainstay for head and pubic lice, with wet combing as an adjunct for head lice.
- Body lice are treated primarily by laundering or discarding infested clothing and improving hygiene rather than treating the skin.
- Eyelash pubic lice are treated with white soft paraffin rather than an insecticide.
- Because a person diagnosed with pubic lice may have another sexually transmitted infection, screening and partner treatment are advised.
Three forms of pediculosis
- **Head lice:** Pediculus capitis, nits on scalp hair, schoolchildren; permethrin and wet combing.
- **Body lice:** Pediculus corporis, live in clothing seams; vector of typhus. Launder clothing.
- **Pubic lice:** Phthirus pubis (crab louse), sexually transmitted; permethrin, screen for STIs.
- **Eyelash lice:** Pubic lice on lashes; treat with soft paraffin, consider abuse in a child.
NMC competencies in this chapter
- **DR6.1:** Aetiology and clinical features of pediculosis
- **DR6.2:** Identifying and differentiating pediculosis from other skin lesions in adults
Frequently Asked Questions
How do you diagnose head lice?
By finding live lice or viable eggs (nits) firmly cemented to hair shafts, most often behind the ears and at the nape of the neck. Nits, unlike dandruff, do not brush off easily.
Why are body lice medically important?
Body lice live in the seams of clothing and act as vectors for epidemic typhus, trench fever and louse-borne relapsing fever, so they matter beyond the itch they cause.
How are pubic lice managed?
Topical permethrin to affected areas, treatment of sexual partners and screening for other sexually transmitted infections. Eyelash involvement is treated with soft paraffin, not an insecticide.
How is body louse infestation treated?
Mainly by washing at high temperature or discarding infested clothing and improving hygiene, because the lice live in clothing rather than on the skin.
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