Lice

1. Epidemiology
   1. Head and body lice are interchangeable
      1. Head Lice (Pediculus humanus capitis)
         1. Female lays eggs at base of hair
         2. Egg adheres as hair grows
         3. Transmitted by fomites or head to head contact
      2. Body lice (Pediculus humanus corpus)
         1. Live in seams of clothing, leave to feed
         2. Transmitted by contact
         3. May carry typhus
   2. Genital Lice: Crab louse (Phthirus pubis)
      1. Often transmitted as Sexually Transmitted Disease
2. Background
   1. Lice is not a sign of uncleanliness
   2. Lice transmits no disease
   3. Main effect of lice is one of embarrassment
   4. Lice do not jump or fly and are not passed by pets
3. Pathophysiology: Lice Life Cycle
   1. Louse Lifetime: 1 month
   2. Lice feed on blood
      1. Typical feeding every 3-6 hours
      2. Survival 15-20 hours without a blood meal
      3. Survival beyond 48 hours without blood meal is rare
   3. Adult female may lay 150 eggs within 1 month (3-10/day)
      1. Female applies strong glue for nit attachment to hair
   4. Nits incubate
      1. Temperature >82 degrees Fahrenheit
      2. Humidity >70%
      3. Viable Embryo
         1. Shows movement within nit
         2. Eye spots may be seen on Embryo
   5. Nits hatch after 7-14 days of incubation
      1. Attach to Hair Shaft adjacent to scalp
      2. Hair Growth moves nit away from scalp
      3. Nit >0.25 inches from scalp is old nit
         1. Not active infestation
      4. Empty nit left when Embryo departs
         1. Distal nit appears flat (missing operculum)
         2. No movement from within nit and no eye spots seen
   6. Nymphs mature into adults by 3 stages over 12 days
   7. Lice life cycle repeats every 3 weeks
4. Pathophysiology: Transmission
   1. Mechanism of transfer
      1. Close contact person to person transmission
         1. Requires direct head contact
      2. Shared inanimate objects (nits survive <2 days)
         1. Combs
         2. Hats
         3. Brushes
         4. Towels
   2. Risks
      1. Ages affected: 3 to 11 years
      2. Brown or red hair color (more than black or blond)
      3. Fine hair
      4. Clean hair on healthy children
      5. Girls more affected than boys
   3. Less affected groups
      1. African Americans rarely affected
5. Symptoms
   1. General
      1. Pruritus is due to allergy to louse Saliva
      2. Pruritus starts at least 2 weeks after infestation
   2. Head Lice
      1. Pruritus at occiput
   3. Body lice
      1. Pruritus may lead to secondary infection
   4. Genital lice
      1. Mild to severe regional Pruritus
6. Signs
   1. Head Lice
      1. Nits visualized with greater ease than lice
      2. Adult lice are 3-4 mm in size (sesame seed size)
      3. Locations (within 1 cm of scalp)
         1. Around and behind ears
         2. Nape of neck
   2. Body Lice
      1. Signs of secondary infection may occur
   3. Genital Lice
      1. Location
         1. Genital region and lower Abdomen
         2. Occasionally axillae or eyelashes
      2. Characteristics
         1. Maculae ceruleae (gray-blue Macules) may occur
7. Management: Medications
   1. First-line Medications
      1. Permethrin 1% (Nix) - OTC
         1. Shampoo hair (no conditioner) and towel dry
         2. Apply Permethrin cream rinse and rinse in 10 min
         3. Repeat in 7-10 days if lice still present
      2. Pyrethrins with Piperonyl butoxide
         1. Apply Shampoo to dry hair and rinse in 10 minutes
         2. Requires second treatment in 7-10 days
      3. Lindane 1%
         1. Not recommended due to Seizure risk in children
   2. Medications used in resistant cases
      1. FDA approved use for Lice
         1. Permethrin 5% (Elimite) - prescription only
         2. Malathion (Ovide) 0.5%
            1. Apply to hair, air dry, wash off in 8-12 hours
      2. Not FDA approved for Lice
         1. Dry-On Suffocation-based Pediculicide (Nuvo Lotion)
            1. Nuvo-Lotion is identical to Cetaphil (OTC)
            2. Applied to hair and hair blow-dried
            3. Nuvo Protocol Resource
               1. http://nuvoforheadlice.com
         2. Trimethoprim-Sulfamethoxazole (Bactrim)
            1. Lower efficacy compared with other agents
         3. Ivermectin (Stomectol)
            1. Initial Dose: 200 mcg/kg PO for single dose
            2. Repeat: 10 days after prior dose
   3. Other agents with historical use
      1. Gamma benzene hexachloride
      2. Crotamiton
   4. Specific Approaches
      1. Head Lice
         1. See Below
      2. Body lice
         1. Clean body, clothing, and bedding
      3. Pediculosis pubis (genital lice)
         1. Permethrin 1% cream (Wash off in 10 minutes)
         2. Screen for other Sexually Transmitted Diseases
8. Management: Protocol for Head Lice
   1. Identify Lice (See signs above)
   2. Use one of medications listed below
      1. First Line: Permethrin 1% Cream rinse
      2. Second Line: Permethrin 5% Cream
      3. Third Line
         1. Consider re-exposure instead of resistance
         2. Reinforce nit removal (see below)
         3. Option 1: Combination therapy
            1. Trimethoprim-Sulfamethoxazole (Bactrim) x10 days
            2. Permethrin 1% (2 applications, 7-10 days apart)
         4. Option 2: Monotherapy with one of agents below
            1. Malathion 0.5% topically (FDA approved)
            2. Ivermectin (not FDA approved)
   3. Remove nits with fine-toothed comb
      1. Use regular comb or brush first to detangle hair
      2. Consider using hair conditioner first
      3. Vinegar or 8% formic acid
      4. Fine-toothed comb (e.g. Licemeister Comb)
         1. http://www.licemeister.org
   4. Reapply medication and remove nits in 7-10 days
   5. Recheck hair for nits over 72 hours
9. Management: Exposure
   1. Risk of transmission is low with casual contact
      1. Contacts have been exposed >1 month at diagnosis
      2. Children may attend school after treatment
      3. Simply avoid direct head to head contact
   2. Avoid embarrassing child
      1. Notify child's parents immediately
      2. Keep diagnosis confidential
      3. Ensure prompt treatment and avoid missing school
   3. Treatment indications
      1. Check household exposures
         1. Live lice or eggs seen within 1 cm of scalp
         2. Treat family members who share same bed as child
      2. Head Lice screening programs are not recommended
         1. Do not reduce Head Lice Incidence
         2. Not cost effective
10. Management: Environmental care (prudent but not proven)
    1. Machine wash all washables in hot water (104 F)
    2. Dry on hot cycle in dryer
    3. Store exposed un-washables in plastic bags for 2 weeks
    4. Vacuum all affected areas
    5. Soak combs and brushes in hot water (130 F) for 15 min
    6. Not necessary to spray furniture with pediculocides
11. Alternative therapies that do not work well
    1. Mechanical "Bug-busting" (wet combing hair for 2 weeks)
    2. Petroleum jelly, Mayonaise, or kerosene (no evidence)
    3. Head shaving has only brief effect
12. Resources
    1. National Pediculosis Association
       1. http://www.headlice.org
       2. Phone: 888-542-3634
    2. Lice Fighting Center (Commercial site)
       1. http://www.lice.com
13. References
    1. Angel (2000) Pediatr Clin North Am 47(4):921-35
    2. Finders (2004) Am Fam Physician 69(2):341-50
    3. Mumcuoglu (1999) Paediatr Drugs 1(3):211-8
    4. Potts (2001) Postgrad Med 110(1):57-64
    5. Ressel (2003) Am Fam Physician 67(6):1391-2
    6. Roberts (2000) Lancet 356:540-4
    7. Roberts (2002) N Engl J Med 346:1645-50
    8. Roos (2001) Drugs 61(8):1067-88