1. Cooties
All About Head Lice
LT Greg Gorman, MC, USNR
Camp Lejeune, NC

2. Lice is a Big Deal
Infests 6-12 million per year, mostly school-aged kids
Does not carry disease, but carries huge social stigma
Biggest problem: Parental Phobia
School Hysteria

3. Know Your Enemy Pediculus humanus var capitis
A blood-sucking insect whose only environment is the human scalp (warm, vascular)
East a blood meal every 4-6 hours
If not on scalp, lice die within 24 hours

4. Know Your Enemy’s Reproductive Cycle
Egg
Nymph
Adult
This determines treatment, how to interpret findings and how to combat parental/school myths and phobias

5. Lice Eggs “Live” eggs are hard to see close to scalp and translucent
Several embryos in one egg
Incomplete nervous system (not affected by drugs)
Need heat to hatch, so always 1-3 mm from scalp
Glued to hair shaft with chitin
Have an “operculum” at top for air and humidity
“Live” eggs are hard to see
close to scalp and translucent
Empty eggs (“nits”) are easier to see
further from scalp as hair grows
inside of egg is reflective
Hatches after 7-12 days

6. Lice Nymphs Smaller than adults Molts 3 times in 8-9 days
Cannot reproduce
Not easily transmitted

7. Adult Lice Big as a sesame-seed; reddish-brown Cannot fly or hop
Cling to hair shaft with 6 claws
Claws evolved to conform to human scalp hair thickness
Lay eggs 1-2 days after becoming adults
Life-span is 30 days

8. Host Factors Lice claws evolved to fit circumference of human hair
Lice are less common in African-Americans, who have oval hair shaft
Crowded living conditions
Hair length is not a factor
(just easier to see nits in longer hair)
Personal hygiene does not play a role

9. Kids are more susceptible
10% of school children have lice
Have more physical contact with peers
10% of infestations occur at school
Usually close friends transmit lice
Girls > Boys (more close contact)

10. Diagnosis of Lice (What to Do When the School Sends Your Kid Home)
Look for a live louse on the scalp
Hard to See
78% of infested kids had 1-10 lice
0.3% had more than 50 lice
Use a comb with 0.3 mm teeth and use a magnifying glass for 5 minutes

11. What if you Find Nits? Nits by themselves are not signs of infestation
(especially after treatment)
Could be hatched already or filled with dead embryos
If nits are close to the scalp and treatment hasn’t been tried, it’s probably active

12. Other Signs of Infestation
Soiled pillows (from lice feces)
Symptoms not typical
Of 501 infested kids,
44% were asymptomatic
36% had pruritus
Itching usually requires sensitization
thousands of bites (~ 3-8 months after infestations starts)

13. Comparison of Head Lice Treatments

14. Lindane Oldest drug (Kwell) No longer on market
Kills lice by interfering with their CNS
Patients can sometimes feel lice convulsing
Requires prescription since inappropriate use can cause seizures
Slower and less effective than other agents

15. Pyrethrin & Permethrin
Derivatives of a natural insecticide derived from chrysantheums
Disrupt Na-channels in CNS
Very low systemic absorption with OTC preparations, but still classified as neurotoxic
Lasts long time by binding to hair, perhaps contributing to resistance

16. How to Treat (Tricks of the Trade)
Safety: Rinse in sink, not shower
Apply to dry hair: the eggs close their operculum in water
Repeat in 7-12 days
After treatment, rinse with 1:1 vinegar:water mixture to dissolve glue and then remove eggs with 0.3 mm tooth comb with 1 1/2 inch teeth
Inspect scalp 48 hrs after treatment to determine what type of lice, if any, are present
A few large lice (maybe resistant)
Many sizes of lice (ineffective treatment)

17. More Tricks of the Trade
Anti-histamines may be useful if itching is severe
Tell parents that itching may occur after treatment and that it is reaction to dead lice and is not a sign of re-infestation
Cleaning & washing inanimate objects
Probably plays no role in getting rid of lice, but if they must...
Drying clothes for 20 minutes before washing them
Seal clothing in bags for 14 days

18. Questionable Folk Treatments
Kerosene: dangerous, ineffective
Smothering: layers of vaseline, olive oil, mayonnaise, or shower cap overnight. Probably not effective and not ovicidal

19. Can Lice Be Resistant?
Incorrect use accounts for majority of treatment failures !!! However,...
Piperonyl-butoxide was added as an inhibitor of pyrethrin-inactivators
In UK, effective doses of drugs increased dramatically since 1948
Lindane: up 200x (Burgess, Advan Parasit 36, 1995)
Permethrin: up 20x (Maunder, J R Soc Health 111, 1991)
In Israel, clinically significant resistance within 3 yrs of permethrin’s introduction (Mumcuoglu, Med Vet Entomol 9, 1995)
In Czech Republic, effective dose of permethrin rose 500x between 1981 and (Rupes, Cent Eur J Public Health 3, 1995)