Head lice infestations Flashcards
What is the latin name for head lice?
Pediculus humanus capitis
Head lice are wingless, 2 mm to 4 mm long (as adults), six-legged, bloodsucking insects that live on the human scalp
What age group is particularly at risk for head lice?
School-aged children
How are head lice different than body lice?
Head lice are not a primary health hazard, a sign of poor hygiene or a vector for disease
How many head lice would a child carry during infection?
Usually ess than 20 mature lice and often less than 10
How long can head lice live?
3-4 weeks on the scalp if untreated
How do head lice feed?
Feed every 3-6 hours by sucking blood and injecting saliva simultaneously
What is the life cycle of a the head lice?
- After mating, the adult female louse can produce five or six eggs (nits) per day for 30 days, each ‘glued’ to a hair shaft near the scalp
- The eggs hatch 9 to 10 days later into nymphs that molt several times over the next 9 to 15 days to become adult head lice
- The hatched empty eggshells remain on the hair but are not a source of reinfestation
How long can head lice live away from the scalp?
Nymphs and adult head lice can survive for only 1 to 2 days away from the human host
While eggs can survive away from the host for up to 3 days, they require the higher temperatures found near the scalp to hatch
What is infestation with head lice called?
Pediculosis
Why does itching occur with a head lice infection?
Sensitization to the saliva of the louse (injected as it feeds)
When does itching occur with head lice infection?
Sensitization can take 4-6 weeks however some people may never have symptoms such as itching
How does transmission of head lice occur?
Direct head to head contact. Lice do not fly but can crawl rapidly.
Fomites are thought to have a controversial role in transmission. Pillowcases are thought to present only a small risk.
Pets are not a vector for head lice.
How is the diagnosis of head lice made?
Presence of a living louse
Presence of nits (eggs) represents a previous infection
Usually examination of the head with a fine tooth comb however can be difficult to differentiate live louse from a nit. A viable nit is most likely to be found less than 0.6 cm from the scalp.
What are the two insecticidal treatments for head lice approved for use in Canada?
1) Pyrethrins- R&C Shampoo and Conditioner
2) Permethrin- Kwellada-P, Nix creme- with 1% permethrin
- Neurotoxic to lice; low toxicity for humans
- Soak for 10 minutes; repeat in 7-10 days (7 days for Nix)
- Rare to have allergic reaction* higher risk in those with ragweed allergy for R&C
- No allergy with Nix
- Both may cause burning or itching sensation with application
Approved for those equal or > 2months with confirmed infection
What are non-insecticidal treatments approved for treatment of head lice in Canada?
1) Isopropyl myristate/ ST-cyclomethicone solution (Resultz rinse)
- Dissolves the waxy exoskeleton of lice, leading to dehydration and death
- Key eyes closed through process and let sit for 10 minutes; rinse off; repeat in 7 days. Flush eye if comes into contact!
NOT recommended for children <4 years of age
2) Dimeticone solution
- 2% concentration of silicone oil dimeticone flows into breathing system to suffocate lice, nymphs and egg embryos
- Leave on 30 minutes; comb well into hair
- Repeat in 8-10 days; low risk for eye irritation
NOT recommended for children < 2 years of age
3) Benzyl alcohol lotion 5% (Ulesfia lotion)
Highly effective against live lice but is not ovicidal
-Second treatment 9 days
-Approved for use in individuals 6 months to 60 years of age, and skin irritation is the only common side effect [27]. This product is quite expensive*
Why are pyrethrins and permethrin thought to be safe?
Minimal percutaneous absorption and favourable safety profiles
- Minimize exposure to other parts of body; do not sit in bath to rinse off; protect skin with towels
Why is lidane no longer used to treat head lice?
Potential for neurotoxicity and bone marrow suppression even with correct use
Is there resistance to head lice treatment?
- Increasing reports of resistance
- Should rule out more common possibilities including misdiagnosis or over diagnosis OR reinvestation after treatment
- If after two permethrin treatments 7 days apart do not eradicate lice then treat with a different class
- Remind families that burning and itching with treatment is NOT a sign of reinfestation* must see live lice!
What medication is not approved for treatment of head lice in Canada?
trimethoprim-sulfamethoxazole
Ivermectin- topical is used in US; not approved in Canada
- Can be taken both orally and topically
- Potentially neurotoxic; not recommended for children <15 kg
Is there evidence for alternative remedies for head lice? What are they?
- Include wet combing and vinegar
- Others include: household products, such as mayonnaise, petroleum jelly, olive oil, tub margarine and thick hair gel
- No evidence to support their use or safety
- Small study for Israel found that a product containing coconut, anise and ylang ylang oils, applied to hair three times at 5-day intervals, was as successful as the control pediculicide
- SHOULD NOT use toxic and dangerous substances such as gasoline or kerosine
Should children with head lice be prevent from attending school?
No! Should alert other parents and prevent “head to head” activity but otherwise should go to school
Is there a role for environmental decontamination?
- Not really
Because lice live close to the scalp, nits are unlikely to hatch at room temperature and environmental cleaning is not warranted - At most, washing items in close or prolonged contact with the head (e.g., hats, pillowcases, brushes and combs) may be warranted
- Wash such items in hot water (≥66°C) and dry them in a hot dryer for 15 minutes. Storing any item in a sealed plastic bag for 2 weeks will kill both live lice and nits [3][11].
What is the role of the health care provider in the management of head lice?
- Are uniquely qualified to dispel myths and provide accurate information on diagnosis, misdiagnosis and management strategies
- Emphasis this is a common problem and does not signify poor hygiene
