Pediculus humanus capitis
From IDWiki
Background
- Human head louse
- Greyish-white insect
- Eggs (nits) are cemented on hair shaft, and hatch in about 8 days
- Moult three times before becoming sexually mature over 8 to 9 days
Epidemiology
- Transmitted by close contact
- Fomite transmission is uncommon, but can happen with hair brushes, combs, clothing, headphones, towels, or bedding
Clinical Manifestations
- Often asymptomatic
- Pruritis can occur due to delayed type IV hypersensitivity reaction to louse saliva
- Initially 2 to 3 weeks to develop, but sooner on repeat infestation
Differential Diagnosis
- White piedra, more common in tropical countries, and surrounds the hair follicle but is much further up on the hair shaft than a nit
- Hair casts from seborrheic dermatitis, which come similar to dandruff but surrounds the follicle, and comes right off unlike a nit
Diagnosis
- Identification of louse in the hair
- May need a louse comb
- One louse is enough for diagnosis
- Found anywhere on the scalp but most commonly nape of the neck and behind the ears
- Nits are laid at the base of the hair follicle, but then moves out as the hair continues to grow
Management
- Permethrin 1% cream rinse
- Wash hair and towel dry
- Saturate hair with permethrin and leave for 10 minutes
- Repeat at 7 to 10 days
- Alternative treatments
- Wet coming using olive oil or hair conditioner, then combing with fine-toothed comb every 3 to 4 days
- Ivermectin
- Head shaving
- Suffocation of lice (not effective)
- Heat treatments (not very effective)
- Electrocution treatments (not very effective)
- Includes vacuum devices
Treatment Failure
- Resistance is rare; much more likely to be:
- Non-adherence to treatment
- Poor application of pediculocide
- Inadequate amount of pediculocide
- Reinfestation
- If treatment failure and was applied properly, can repeat treatment with an alternative agent
Prevention
Infection Prevention and Control
- Treat any infected contacts
- Treat bunkmates empirically
- Wash any clothing and bedding that was used by the infested patient within the past 48 hours
