Lice (Pediculosis)

Lice (Pediculosis): Excerpt from The 5-Minute Pediatric Consult

J. Nadine Gracia, MD

Lice - BASICS

Lice - description

Infestation of the head, body, or anogenital region with 1 of 3 species of lice

Lice - general prevention

Head lice is not preventable.

Lice - epidemiology

• Head lice:
  • Common in day care setting and school-age children
  • Affects all socioeconomic groups
  • Not indicative of poor hygiene
• Body lice:
  • Found on persons with poor hygiene
  • More common in extreme conditions such as crowding, homelessness
• Pubic lice:
  • Most common in adolescents and young adults

Lice - incidence

Estimated 6–12 million cases per year in US

Lice - risk factors

Head lice infestation not influenced by hair length or frequency of shampooing or brushing.

Lice - pathophysiology

• Head lice:
  • Survive for 3–4 weeks on scalp
  • Typical infestation, 12–24 live insects per patient
  • Louse can produce 300 ova in its lifetime
  • Ova (nits) laid close to the scalp; firmly attached to hair shaft by chitinous ring (usually clustered in the parietal and occipital areas); camouflaged to match hair color
  • Ova hatch after 10–14 days, leaving white shell of nit on hair (readily visible to examiner)
  • Transmitted by direct contact with infested hair or much less commonly fomites (e.g., combs, hairbrushes, hats, bed linens, clothing, headsets)
  • Prefer to feed on scalp skin; hook onto scalp, pierce skin to feed on human blood
  • Inject saliva that causes pruritus, dermatitis
  • Survive 1–2 days away from scalp
• Body lice:
  • 10–20% larger than head lice
  • Prefer to live on clothing, visiting human only to feed
  • Lay eggs along seams of clothing, which hatch when warmed by wear
  • Incubation period 6–10 days
  • Transmitted through contact with infested clothing or bedding
  • Survive off human host up to 10 days
• Pubic lice:
  • Crablike appearance with predilection for pubic hair
  • May also infest axillary hair, perineal area, eyelashes, eyebrows, and rarely scalp
  • Transmitted almost exclusively by sexual contact
  • Uncommonly spread by fomites (e.g., towels, bedding)
  • May infest eyebrows/lashes (pediculosis palpebrarum) in young children (associated with maternal infestation, but must consider possible sexual abuse)

Lice - etiology

3 species of ectoparasites (6-legged, wingless, 1–4-mm insects that live on humans, feeding on human blood): Note: Lice do not fly or hop, but crawl to move around.

• Pediculus humanus capitis: Head louse
• Pediculus humanus corporis: Body louse
• Phthirus pubis: Pubic or crab louse

Lice - associated conditions

• Head lice: Do not transmit disease; rarely scalp impetigo, cervical and occipital lymphadenopathy may develop.
• Body lice: Can transmit disease (e.g., endemic typhus, trench fever, relapsing fever) or secondary bacterial skin infections due to pruritis.
• Pubic lice: Up to 50% of patients have another STD, particularly gonorrhea or syphilis.

Lice - DIAGNOSIS

Lice - signs & symptoms

Lice - history

• Pruritus: Itching is the most common symptom; however, some patients are asymptomatic.
• Intense nighttime pruritis common with body lice.
• Secondary skin lesion (from scratching): May be chief complaint
• Special questions:
  • Ask about possible infested contacts (home, school, or sexual).
  • Ask about special living circumstances such as crowding or institutionalization.

Lice - physical exam

• Lice (difficult to find) on the scalp, in the pubic hair, or in the seams of clothing: Gold standard for diagnosis.
• Nits:
  • Clustered in parietal and occipital regions, in the perianal region, or in the seams of clothing
  • Difficult to flick away (unlike dandruff, hair casts, or debris); need to be pulled along entire length of hair shaft to remove
• Primary skin lesion:
  • Pinpoint, erythematous macule, papule, or urticarial wheel
  • Can be obliterated by scratching
• Other findings:
  • Secondary skin lesions (e.g., impetigo, excoriation); dermatitis of the neck, shoulder area
  • Examine eyelashes, eyebrows for secondary infestation.
  • Cervical or occipital lymphadenopathy with head lice
  • Postinflammatory hyperpigmentation with body lice
  • Maculae cerulae (sign of heavy pubic infestation): Bluish/slate macules, 0.5–1-mm diameter

Lice - tests

• Tests rarely necessary. Can examine louse or nit using hand lens or under microscope. Dandruff is a false-positive finding.
• Home testing: Parents can be instructed how to examine all family members by using a fine-tooth plastic comb from the scalp to the end of the hair looking for lice and/or nits.
• School testing: Schools can perform examinations during epidemics. Routine school screening is not recommended.

Lice - differencial diagnosis

• Seborrheic dermatitis
• Contact dermatitis
• Eczema
• Impetigo
• Scabies

Lice - TREATMENT

Lice - general measures

• Head lice:
  • Wash hair with nonconditioning shampoo and towel dry
  • Apply pediculicide to dry hair
  • If nit removal desired, soak hair with white vinegar for 30 minutes, followed by combing with a fine-tooth nit comb.
  • Examine household members and treat those who are infested.
  • Prophylactically treat bed mates.
  • Environmental cleaning: This is controversial and may not be necessary:
    • Wash bedding, clothes, and cloth toys in hot water (>128°F).
    • Treat combs and hairbrushes by washing in hot water and soaking in pediculicide.
    • Seal anything not washable in plastic bags for 14 days.
    • Nit removal not necessary, especially if pediculicide reapplied 1 week later
    • Environmental insecticide is not helpful in the control of head lice.
    • Floors and furniture can be vacuumed if desired.
• Body lice:
  • Pediculicide not necessary (insects live in clothing)
  • Improve hygiene.
  • Wash clothing and bedding in hot water at least weekly.
  • Dry cleaning is effective, as is hot ironing (particularly along seams of clothing).
• Pubic lice:
  • Apply pediculicide and retreat 7–10 days later with pediculicide
  • Treat sexual contact to prevent reinfestation.
  • Removal of nits from pubic hair with fine-tooth comb helpful
• Pediculosis palpebrarum
• Petrolatum ointment applied to lashes 2–4 per day for 8–10 days
• Remove nits by hand from the eyelashes.

Duration: The pediculicide kills the lice shortly after application; therefore, living lice after treatment is indicative of incorrect use of the pediculicide, very heavy infestation, reinfestation, or resistance to therapy. Retreatment with a second pediculicide with reapplication 7–10 days later is recommended.

Lice - activity

• School attendance: “No-nit” school policies do not control head lice transmission and are not recommended. Children who have been treated with appropriate pediculicide should be allowed to return to school.
• No data to determine whether suffocation of lice by application of petroleum jelly, olive oil, or mayonnaise is effective.
• Nonchemical treatment currently under study: 30-minute application of hot air to scalp (via blow-dryer or custom-built machine) effectively eradicates head lice infestation.

Lice - medication

Head and pubic lice:

• Permethrin (Nix) 1% cream rinse:
  • Acts on nerve cell membranes, causing paralysis/death of louse
  • Generally used as first-line therapy
  • 10-minute application, followed by 2nd application 7–10 days later
  • Resistance documented in US but prevalence unknown
  • High cure rate; prevalence to resistance in the US is unknown.
  • OTC preparation, low toxicity
• Pyrethrins (Rid, A-200):
  • Neurotoxin also, low ovicidal activity
  • Resistance documented in the US
  • 10-minute shampoo application, 2nd application 7–10 days later
  • OTC preparation
  • Contraindicated in persons allergic to chrysanthemums or ragweed
• Malathion (Ovide) 0.5%:
  • Better ovicidal activity, highly effective
  • Probably most effective treatment available but safety concerns; minimal resistance
  • Requires 8–12-hour application; 2nd application 7–10 days later only if live lice present
  • Less toxicity than lindane and pyrethrins
  • Safety concerns: Flammability (alcohol base) and respiratory distress if ingested
• Lindane (Kwell) 1% lotion:
  • Should no longer be used owing to neurotoxicity, lack of efficacy
• Other treatments:
  • Sulfamethoxazole–trimethoprim (Bactrim) with permethrin 1% has slightly improved cure rate. 10-day course reserved for treatment failures. Not FDA approved as pediculicide.
  • Ivermectin: Oral single dose 200 mcg/kg followed by 2nd dose 7–10 days later may be effective for heavy infestations, but it is not FDA approved for this. Do not use in patients <15 kg because it blocks neural transmission if it crosses blood–brain barrier (younger children at higher risk).
  • Albendazole: 2003 study demonstrating effectiveness of albendazole against head lice but not FDA approved for this use. No synergistic effect between albendazole and 1% permethrin.
• Other considerations:
  • Topical corticosteroids and oral antihistamines for pruritis and inflammation
  • Antibiotics for impetiginized lesions

Pediculosis palpebrarum:

• Pediculicides are oculotoxic and must be avoided.

Lice - FOLLOW UP

When to expect improvement:

• Risk of transmission is promptly reduced after single application, so child should be allowed to return to school or day care.
• Removal of nits is not necessary to reduce spread nor to return to day care/school.
• Pruritus may persist for 2 weeks after therapy.

Lice - prognosis

Excellent

Lice - patient monitoring

Signs to watch for: Recurrence of symptoms represents improper use of the treating agent, reinfestation, resistance, failure to recognize and treat other sites of infestation, such as perianal hair, axillary hair, or sexual contacts: Pediculosis pubis.

Lice - bibliography

1. Akisu C, Delibas SB, Aksoy U. Albendazole: Single or combination therapy with permethrin against pediculosis capitis. Pediatr Dermatol. 2006;23:179–182.
2. American Academy of Pediatrics. Head lice: Clinical Report. Pediatrics. 2002;110:638–643.
3. Dirk E. Drug-resistant lice. Arch Dermatol. 2003;139:1061–1064.
4. Goates BM, Atkin JS, et al. An effective nonchemical treatment for head lice: A lot of hot air. Pediatrics. 2006;118:1962–1970.
5. Meinking TL, Clineschmidt CM, Chen C, et al. An observer blinded study of 1% permethrin crème rinse with and without adjunctive combing in patients with head lice. J Pediatr. 2002;141:665–670.
6. Meinking TL, Serrano L, et al. Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States. Arch Dermatol. 2002;138:220–224.
7. Roberts R. Head lice. N Engl J Med. 2002;345:1645–1650.

Lice - CODES

Lice - icd9

• 132.0 Capitis (head louse, any site)
• 132.0 [373.6] Eyelid
• 132.1 Vestimenti
• 132.1 Corporis (body louse, any site)
• 132.2 Vulvae
• 132.2 Pubis (pubic louse, any site)
• 132.9 Pediculosis (infestation)

Lice - FAQ

• Q: Did my child get head lice because my house or my child is not clean enough?
• A: No, head lice is unrelated to personal hygiene. Some experts even believe lice prefer a clean scalp.
• Q: Should I cut my child’s long hair to get the lice out?
• A: No, meticulous application of the pediculicide to the entire scalp and pulling through all hair shafts is adequate treatment. Urgently cutting a child’s hair can be traumatizing to the child. Head lice infestation is not influenced by hair length.
• Q: Can infants become infested with pubic lice (Phthirus pubis)?
• A: Yes. Although the primary mode of transmission of the crab louse is via sexual contact, it can be transmitted through close personal contact with an infested individual. Small children become infested on the eyebrows or lashes with crab lice.
• Q: If children are infested with the head louse, how can items such as stuffed animals or other cloth toys be decontaminated?
• A: Machine washable items can be washed in hot water at temperatures >128°F. An alternative method of decontamination is sealing the items in a plastic bag for 10–14 days.
• Q: Is removal of nits necessary to prevent spread?
• A: No. They can be removed for a cosmetic reasons by using a fine-tooth comb or by soaking the hair in a solution of white vinegar followed by wrapping the head with a towel soaked in the same solution for 30–60 minutes.
• Q: What is appropriate treatment of infestation of the eyelashes?
• A: A petroleum ointment should be applied 2–4 times daily for 8–10 days. Nits should be removed mechanically from the lashes.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Head lice

• Back to disease: Head lice: Introduction
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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