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Pediculus capitis (head louse)

Epidemiology: 1) transmitted directly from person to person & by shared hats & combs or brushes - lice are not able to jump or fly [7] 2) prevalence is greatest in school-aged girls with long hair 3) black children are less frequently affected than other children 4) females firmly cement their eggs to hair 5) nits or eggs generally hatch in 8-9 days 6) see ref [2] for pictures Clinical manifestations: 1) excoriations of pruritic lesions on the scalp, neck & shoulders leading to: a) oozing b) crusting c) matting of hair d) bacterial infections e) regional lymphadenopathy 2) examination: - combing through wet, conditioned hair with a fine-toothed comb (scalp inspection is insufficient) [3] Management: 1) do not treat a child unless live lice or eggs (not just empty nit cases) are present 2) topical permethrin 1% or malathion 0.5% a) kills lice & most eggs, but will not kill newly laid eggs that have not yet developed a nervous system [7] b) apply & leave on overnight, rinse in morning c) combine with nit combing [12] d) up to 2 additional treatments spaced 9 days apart may be needed [7] e) at least 1 additional treatment 9 days later recommended [11] 3) piperonyl butoxide/pyrethrin (4%/0.3%) shampoo [12] - apply to damp hair for 10 minutes, then rinse - repeat in 1 week - combine with nit combing [12] 4) 1% lindane or 5% benzyl alcohol lotion - apply & leave on overnight, rinse in morning - NOT ovicidal & require a 2nd application after 9 days to kill hatching nymphs 5) spinosad (Natroba) FDA-approved Jan 2011 - apply to affected area for 10 minutes, then rinse - repeat in 1 week - nit combing not necessary [12] 6) ivermectin a) 12 mg PO weekly, 3 doses b) 200 ug/kg single dose is effective [4,5] c) topical lotion 0.5% (Sklice) once [10] d) nit combing not necessary [12] 7) diethylcarbamazine, albendazole probably ineffective [4] 8) comb hair after treatment with fine-toothed nit comb to remove nits 9) combs & brushes should be disinfected in hot water at 65 degrees C for 5 minutes or soaked in insecticide for 1 hour 10) in areas with proven resistance, parents may consider manual methods such as wet-combing or using petroleum jelly to suffocate the lice [11] 11) children should miss school because of head lice; odds of transmission are low [11]

Related

lindane (Kwell, Scabene) pediculosis; phthiriasis (lice infestation, vagabond disease) permethrin (Elimite, Nix)

General

Pediculus

Properties

KINGDOM: animal PHYLUM: arthropod ORGANISM-CLASS: INSECTA ORDER: anoplura FAMILY: pediculidae GENUS: Pediculus

References

  1. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 935-36
  2. Roberts RJ. Clinical practice. Head lice. N Engl J Med. 2002 May 23;346(21):1645-50. Review. Picture of louse & of unhatched nit. No abstract available. PMID: 12023998
  3. Jahnke C et al Accuracy of Diagnosis of Pediculosis Capitis: Visual Inspection vs Wet Combing Arch Dermatol 2009 145(3) March 2009 PMID: 19289764 http://archderm.ama-assn.org/cgi/content/short/145/3/309
  4. Munirathinam A et al. Impact of ivermectin drug combinations on Pediculus humanus capitis infestation in primary schoolchildren of south Indian rural villages. Int J Dermatol 2009 Nov; 48:1201. PMID: 20064176
  5. Chosidow O et al. Oral ivermectin versus malathion lotion for difficult-to- treat head lice. N Engl J Med 2010 Mar 11; 362:896 PMID: 20220184
  6. Prescriber's Letter 17(5): 2010 COMMENTARY: Ivermectin (Stromectol) for Head Lice GUIDELINES: Diagnosis and Treatment of Head Lice (NGC Summary, 2008) PATIENT HANDOUT: Treating Head Lice PATIENT HANDOUT SPANISH VERSION: El Tratamiento de Piojos de la Cabeza Detail-Document#: 260523 (subscription needed) http://www.prescribersletter.com
  7. Prescriber's Letter 17(9): 2010 COMMENTARY: Treatment of Head Lice - An Update PATIENT HANDOUT: Treating Head Lice PATIENT HANDOUT SPANISH VERSION: El Tratamiento de Piojos de la Cabeza GUIDELINES: Head Lice Detail-Document#: 260911 (subscription needed) http://www.prescribersletter.com
  8. Prescriber's Letter 18(9): 2011 Commentary: Natroba (Spinosad) for the Treatment of Head Lice Patient Handout: Treating Head Lice Detail-Document#: 270904 (subscription needed) http://www.prescribersletter.com
  9. Frankowski BL et al, Council on School Health and Committee on Infectious Diseases American Academy of Pediatrics Head Lice Pediatrics 2010 126:392-403 PMID: 20660553 http://pediatrics.aappublications.org/content/126/2/392.full.html
  10. Pariser DM et al Topical 0.5% Ivermectin Lotion for Treatment of Head Lice N Engl J Med 2012; 367:1687-1693 PMID: 23113480 http://www.nejm.org/doi/full/10.1056/NEJMoa1200107 - Chosidow O and Giraudeau B Topical Ivermectin - A Step toward Making Head Lice Dead Lice? N Engl J Med 2012; 367:1750-1752 PMID: 23113487
  11. Devore CD, Schutze GE. COUNCIL ON SCHOOL HEALTH AND COMMITTEE ON INFECTIOUS DISEASES. Head Lice Pediatrics. April 27, 2015 PMID: 25917986 http://pediatrics.aappublications.org/content/early/2015/04/21/peds.2015-0746
  12. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015