Head lice infestations: A clinical update

Question 1

What is head lice?

Answer 1

Pediculus humanus capitis

Question 2

How many nits can be produced per day by an adult female head lice?

Answer 2

5-6 eggs per day for 30d

Question 3

How long does it take for eggs to hatch?

Answer 3

9-10d

Question 4

How long does it take for a hatched nymph to mature into an adult head lice?

Answer 4

9-15d

Question 5

How long does an adult lice live?

Answer 5

3-4 weeks in hair

Question 6

How often do head lice feed?

Answer 6

q3-6h from sucking blood

Question 7

How long can nymph and adult head live survive for only 1-2d away from the human host?

Answer 7

1-2d

Question 8

How long can eggs survive away from the human host?

Answer 8

up to 3d but cannot hatch without being on the scalp

Question 9

What is an infestations with lice?

Answer 9

Pediculosis usu. involves <10 live lice

Question 10

How long does it take for sensitization?

Answer 10

4-6 weeks

due to sensitization to antigenic components in the saliva of louse

Question 11

How is head lice transmitted?

Answer 11

Direct hair to hair contact (cannot hop or fly, crawl 23cm/min)
No transmission by fomites or pets

Question 12

How do you diagnose pediculosis?

Answer 12

Detection of a living louse

Question 13

What are the risks of Lindane?

Answer 13

Neurotoxicity
Bone marrow suppression
Carcinogen?

Question 14

What are side effects of topical insecticides?

Answer 14

Scalp rash, itching or mild burning sensation

Question 15

What are examples of topical insecticides?

Answer 15

Pyrethrins and permethrin 1%
Not available in Canada:
Malathion lotion 0.5%
Crotamiton lotion 10%

Question 16

How does Resultz (isopropyl myristate 50% and ST-cyclomethicone 50%) work?

Answer 16

Dissolves the insect’s waxy exoskeleton causing dehydration and death
Not ovicidal

Question 17

How does NYDA (92% silicone oil dimeticone) work?

Answer 17

Affects the insect’s breathing apparatus and is effective against lice, nymphs, and egg embryos

Question 18

How effective is wet combing?

Answer 18

38%

Question 19

What is the first line therapy for head lice in Canada?

Answer 19

1. Pyrethrin 1% (R&C shampoo) repeat treatment 7-10d later
2. Permethrin 1% (Kwelleda or Nix) repeat 7d later

Question 20

What are the second line therapies for head lice?

Answer 20

1. 50% Isopropyl myristate/ 50% ST-cyclomethicone (Resultz) repeat in 7d
2. 92% silicone oil dimethicone (NYDA) repeat in 8-10d
3. 5% benzyl alcohol lotion (Ulesfia) repeat in 9d

Question 21

At what age can first line therapies be used?

Answer 21

> 2mo

Question 22

At what age can Resultz be used?

Answer 22

> 4yo

Question 23

At what age can NYDA be used?

Answer 23

> 2yo

Question 24

At what age can Ulfesia be used?

Answer 24

6m-60yo

Question 25

What are the recommendations for children in school or child care with lice?

Answer 25

No exclusion from school or child care

Question 26

Who should be informed when a child has active head lice?

Answer 26

Families of children in the same classroom or child care group

Question 27

What are the recommendations regarding environmental cleaning?

Answer 27

Not recommended
Consider washing items in close or prolonged contact with the head in hot water >66degrees or dry them in a hot dryer for 15min
Storing any item in a sealed plastic bag for 2 weeks will kill both live lice and nits

Question 28

What are the recommendations regarding head lice education?

Answer 28

1. Head lice infestations are common in school-children but are not associated with disease spread or poor hygiene.
2. Head lice infestations can be asymptomatic for weeks.
3. Misdiagnosis of head lice infestations is common. Diagnosis requires detection of live head lice. Detecting nits alone does not indicate active infestation.
4. Environmental cleaning or disinfection following the detection of a head lice case is not warranted. Head lice or nits do not survive for long away from the scalp.

Question 29

What are the recommendations regarding lice treatment?

Answer 29

1. Treatment with an approved, properly applied, topical head lice insecticide (two applications seven to 10 days apart) is recommended when a case of active infestation is detected.
2. When there is evidence of treatment failure – detection of live lice – using a full course of topical treatment from a different class of medication is recommended.
3. The scalp may be itchy after applying a topical insecticide but itching does not indicate treatment resistance or a reinfestation.
4. Topical insecticides can be toxic. Take care to avoid unnecessary exposure and, when indicated, minimize skin contact beyond the scalp.
5. Excluding children with nits or live lice from school or child care has no rational medical basis and is not recommended.
6. For children ≥2 months of age, permethrin and pyethrins are acceptable treatments for confirmed cases of head lice. Dimethicone can be used in children ≥2 years of age. Myristate/ST-cyclomethicone can be used in children ≥4 years of age. Benzoyl alcohol lotion is comparatively expensive but can be used in children ≥6 months of age.

Question 30

What are the recommendations regarding school and child care facilities regarding head lice?

Answer 30

Excluding children with nits or live lice from school or child care has no rational medical basis and is not recommended.