- 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 Enemys Reproductive Cycle
- This determines treatment, how to interpret findings and how to
combat parental/school myths and phobias
Egg Nymph Adult 5. Lice Eggs 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
- Molts 3 times in 8-9 days
7. Adult Lice
- Big as a sesame-seed; reddish-brown
- Cling to hair shaft with 6 claws
- Claws evolved to conform to human scalp hair thickness
- Lay eggs 1-2 days after becoming adults
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 isnota factor
- (just easier to see nits in longer hair)
- Personal hygiene doesnotplay 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
- 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 hasnt been tried,
its probably active
12. Other Signs of Infestation
- Soiled pillows (from lice feces)
- Itching usually requires sensitization
- thousands of bites (~ 3-8 months after infestations
starts)
13. Comparison of Head Lice Treatments 14. Lindane
- 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 todryhair: the eggs close their operculum in water
- 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
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- A few large lice(maybe resistant)
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- 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...
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- Drying clothes for 20 minutes before washing them
-
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- 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
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- 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
permethrins introduction(Mumcuoglu, Med Vet Entomol 9, 1995)
- In Czech Republic, effective dose of permethrin rose 500x
between 1981 and 1992(Rupes, Cent Eur J Public Health 3, 1995)