Head lice infestations

Question 1

What is the latin name for head lice?

Answer 1

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

Question 2

What age group is particularly at risk for head lice?

Answer 2

School-aged children

Question 3

How are head lice different than body lice?

Answer 3

Head lice are not a primary health hazard, a sign of poor hygiene or a vector for disease

Question 4

How many head lice would a child carry during infection?

Answer 4

Usually ess than 20 mature lice and often less than 10

Question 5

How long can head lice live?

Answer 5

3-4 weeks on the scalp if untreated

Question 6

How do head lice feed?

Answer 6

Feed every 3-6 hours by sucking blood and injecting saliva simultaneously

Question 7

What is the life cycle of a the head lice?

Answer 7

• 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

Question 8

How long can head lice live away from the scalp?

Answer 8

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

Question 9

What is infestation with head lice called?

Answer 9

Pediculosis

Question 10

Why does itching occur with a head lice infection?

Answer 10

Sensitization to the saliva of the louse (injected as it feeds)

Question 11

When does itching occur with head lice infection?

Answer 11

Sensitization can take 4-6 weeks however some people may never have symptoms such as itching

Question 12

How does transmission of head lice occur?

Answer 12

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.

Question 13

How is the diagnosis of head lice made?

Answer 13

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.

Question 14

What are the two insecticidal treatments for head lice approved for use in Canada?

Answer 14

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

Question 15

What are non-insecticidal treatments approved for treatment of head lice in Canada?

Answer 15

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*

Question 16

Why are pyrethrins and permethrin thought to be safe?

Answer 16

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

Question 17

Why is lidane no longer used to treat head lice?

Answer 17

Potential for neurotoxicity and bone marrow suppression even with correct use

Question 18

Is there resistance to head lice treatment?

Answer 18

• 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!

Question 19

What medication is not approved for treatment of head lice in Canada?

Answer 19

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

Question 20

Is there evidence for alternative remedies for head lice? What are they?

Answer 20

• 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

Question 21

Should children with head lice be prevent from attending school?

Answer 21

No! Should alert other parents and prevent “head to head” activity but otherwise should go to school

Question 22

Is there a role for environmental decontamination?

Answer 22

• 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].

Question 23

What is the role of the health care provider in the management of head lice?

Answer 23

• 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