Lice

FAQs for Health Care Providers

Lice: Risk, Diagnosis, and Treatment in Afghan Evacuees

Have there been confirmed cases in the Afghan evacuees? Yes, head lice

Epidemiology

• In the U.S., the prevalence of head lice is highest between children 3-12 years of age

• Prevalence is higher in resource limited settings, with low socioeconomic status and in crowded conditions such as being experienced by Afghan evacuees

When should I consider pediculosis?

Clinical Presentation

Head louse infestation presents with scalp itching, and sometimes posterior cervical lymphadenopathy. The lice and nits can be seen by combing through hair.

Body louse infestation can present as a generalized itching and dermatitis that can mimic a viral exanthem. Body lice can carry diseases such as louse-borne relapsing fever, trench fever, and epidemic typhus.

Pubic lice, or “crab lice,” are found on hair in the pubic, chest, abdominal, and leg areas. They may also be present on facial hair, including the beard, eyelashes and eyebrows. The typical skin lesion is blue-gray macules on the abdomen and thighs.

Is pediculosis contagious? Yes - Head lice spreads through direct hair-to-hair contact, and the risk is higher with prolonged exposure. It can also spread through fomites such as hats or scarves. Pubic lice can be transmitted during sexual contact. Lice do not jump or fly, and household pets do not transmit human lice.

Are there special infectious disease precautions?

• Standard contact precautions are recommended.

• If close hair-to-hair contact is expected (such as when doing an otoscopic exam), it is reasonable to tie one’s hair back or wear a surgical cap.

• No quarantine or public health reporting is needed although if planning to move into a new household or congregate living, expert consultation should be obtained (if during medical intake/screening examination, please contact infectious diseases on call).

How do I diagnose pediculosis?

• Use a fine-toothed comb to examine the hair (scalp and pubic) for the following:

  • Head lice are 1-4 mm in size and visible to the naked eye with close inspection

  • Actively moving lice (they move quickly and away from light)

  • There is a higher chance of finding lice behind the ears, on the back of the head, or nape of the neck

  • Nits containing live eggs are located on the hair shaft within 1-2 mm of the scalp. They are firmly adherent, unlike dandruff. Nits further from the scalp may not contain viable eggs.

• Body lice can cause a generalized rash

  • Examine the seams of clothing for live lice or nits. Live lice are rarely seen on the skin.

  • Skin lesions may include small red macules, papules, or wheals (hives) with a hemorrhagic central punctum. They may be heavily excoriated and/or impetiginized with bacteria.

• Pubic lice have short bodies resembling crabs; see image

What is the treatment for pediculosis?

• Head lice are increasingly resistant to over-the-counter treatments. Most treatments must be repeated 2-3 times, as they may kill live lice, but may not kill the eggs.

• Shaving all of the infested hair will eliminate scalp and pubic infestation, though this is usually not cosmetically preferred.

• Close contacts of a person diagnosed with active infestation should be checked for head lice and treated if appropriate.

• First line treatment (for ages 6 months to 60 years): Benzyl alcohol 5% lotion

  • Kills live lice, but not eggs

  • Must be applied to dry hair

  • Saturate all hair and leave on for 10 minutes

  • Rinse off in sink to avoid contact with entire body

  • Repeat dose in 7 days

  • Side effects include irritant and allergic contact dermatitis. Exceptionally high topical doses (>99 mg/kg/day) can cause “gasping syndrome” in children due to systemic absorption (CNS depression, irregular respirations, and metabolic acidosis).

  • Alternative regimen (see CDC link below for additional treatments and more information)

  • Permethrin lotion, 1% topical (over the counter)

  • Resistance is widespread

  • Approved for ages 2 months and older

  • Kills live lice but not eggs

  • Repeat treatment on day 9; may require a third treatment

  • Do not use shampoo or conditioner prior to applying permethrin lotion

  • If pubic lice are found, the patient should also be tested for chlamydia and gonorrhea due to high co-occurrence

  • Lice do not survive long once they fall off a human and cannot feed

  • Wash clothing, sheets, headscarves, and hats with hot water and a hot dryer cycle

  • If unable to launder, place items in a sealed plastic bag for 2 weeks

  • Soak combs and brushes in hot water (at least 130 F) for 5-10 minutes

Resources and References

• CDC: general information on Lice

• UpToDate: Pediculosis capitis

• Principles and Practice of Pediatric Infectious Diseases, by Sarah Long. Chapter 257: Ectoparasites (Lice and Scabies)

Contributors

Kristen Bastug, MD

Alexia Knapp, MD

William Stauffer, MD