Wet combing for head lice: feasibility in mass screening, treatment preference and outcome

Abstract

There is no scientific consensus on the best way to control head louse infestation in schoolchildren. A study was conducted to test the feasibility and acceptability of a screening campaign by wet combing and a community approach to head-louse control with home visits, and to explore parents' treatment preferences and treatment outcomes. A non-controlled intervention (advice on treatment options offered to all positive children) was nested within an epidemiological prevalence study. All children in three primary schools in Ghent, Belgium, were invited to take part in screening by wet combing (n=677, 3-11 years). Positive children were offered structural treatment advice, a home visit on day 7, and a check by wet combing on day 14.

83% of the children were screened. The prevalence of active infestation (living moving lice) was 13.0% in school 1 and 19.5% in school 3. In school 2, prevalence of signs of active and past infestation was 40.7%. A home visit was made to 58% of the positive children. 85% of the positive children were screened again on day 14. Wet combing was the most widely used treatment, followed by chemical treatment and a combination of the two. In school 1 and 3 51% were cured, and in school 2 24% became nit-free. A wet combing screening campaign and a community-oriented approach to head-louse control is feasible though resource-intensive. The prevalence of head lice was high and the cure rate was low, with either topical treatments or wet combing.

INTRODUCTION

Infestation with head lice is a harmless but troublesome condition, mainly affecting children aged 3-11 attending kindergarten and primary school. In Western European countries, prevalence rates are usually something under 10%^{1,2,3,4,5,6,7}. A common reason for visiting a pharmacist is to obtain head lice treatment⁸. Most infested children remain symptom-free and are not bothered by itching⁹. The old method of dry-hair scalp inspection can miss up to 10% of infestations; on the other hand, false criteria for the diagnosis of louse infestation (presence of empty egg cases) in no-nits policies will lead to overdiagnosis and consequent mismanagement^11,12.

Schools have tried different approaches, from ignoring the problem, to educational campaigns, a severe ‘no-nit-policy’ or a frantic ‘oust the louse’ campaign^12,13. There are scant published data to sustain the development of an evidence-based strategy. Research activity with clinical trials has virtually stopped in the last decade. Vital information from certain trials has remained unpublished, despite exposure of publication bias¹⁴. Experts disagree on the interpretation of the little information available^14,15.

The objectives of our study were to measure the prevalence of louse infestation with a wet combing screening campaign, to test the feasibility and acceptability of a structured community-oriented health service approach for the control of head lice epidemics in primary schools, to explore treatment preferences among patients, and to examine the outcomes of the chosen treatments.

The setting for this study was the city of Ghent, an industrialized town of 224 160 citizens, with 9.6% children between the ages of 3 and 11 years. The city is situated in the Dutch speaking part of Belgium. The study was an epidemiological prevalence study with a non-controlled intervention (advice on treatment options given to all positive children).

METHODS

In a convenience sample of three schools in Ghent, all 677 children (aged 3-11 years) were invited to take part in a screening campaign with wet comb testing (combing of lavishly conditioned wet hair in systematic sweeps with a fine-toothed comb). In addition, a coordinated programme was set up between the schools and community organizations, supplemented by a health education campaign and a management protocol for the attendance, treatment, and follow-up of families with infested children; this part of the project was initiated by the social workers and community nurses of three community healthcare centres. Programme design was based on the methodology of ‘community-oriented primary care’¹⁶, characterized by involvement of the community and empowerment of the target population. The programme was aimed at children, parents, school personnel, head teachers, school health departments and health and community care professionals.

One week before the screening, parents received a letter with information about the project, asking them to consent and participate, and to get their children to bring a towel on the day of screening. In schools 2 and 3, parents' permission was assumed in the absence of written refusal. All children present in the schools during the screening period were screened with the wet combing method. In school 3, wet combing screening was preceded by visual inspection of dry hair, as part of a study to evaluate the performance of diagnostic strategies (reported elsewhere¹⁰). In the week of the screening, the children's regular teachers provided a 2-hour lesson on head lice (including rehearsal of a louse song).

The parents of the positive children were informed by letter and were given a pamphlet with treatment options and a louse comb. They were offered structured treatment advice, a home visit on day 7, and a check by wet combing on day 14. A video (including explanation of the wet combing method) was available on request. The stated options for treatment were either a chemical agent (permethrine 1% creme rinse, 10 minutes¹⁴; malathion 0.5% lotion, 12 hours¹⁴; or synergized pyrethrine spray depallethrine 0.66%+piperonyl butoxide 2.64%, 30 minutes)¹⁷ or the wet combing treatment technique (a wet combing session every 4-5 days for two weeks)¹⁸. No recommendation was made on which of these would be best. Parents were invited to screen themselves, other children and family members, and to treat only those with active infestation. Hot washing of clothes, or fumigation of furniture, clothes or carpets, was not recommended^1,7. Box 1 shows the recommended schedules for wet combing and chemical treatment over 14 days.

Box 1.

Timing of wet combing and chemical treatment in a two week cycle of diagnosis, treatment and control

Day	Wet combing	Chemical treatment
0	Screening at school (also first treatment session)	Treatment at home (on the same day or the day after, if product action sensitive to conditioner)
4 or 5	Wet combing session at home
7		Check; reapplication of same substance if positive
9 or 10	Wet combing session at home
14	Wet combing session at school (last of four therapeutic sessions and check); reapplication of wet combing method or shift to chemical treatment if positive	Check; application of another substance or method if positive

Parents of positive children were informed by letter that a home visitor would come to their house the following week (if possible on day 7). These home visitors were selected from local social workers and community nurses, who got permission to participate in the project during working hours. They were called ‘sherpas’ (by analogy with the Nepalese mountain guides) to label them as experienced and empathic emissaries and to distinguish these home visits clearly from inspection activities by persons with potential police authority. On arrival at a child's home, sherpas asked permission to enter. If admitted, they gathered information on past and current experience with head lice control through a structured questionnaire, but they did not check the children or family members for infestation unless explicitly asked. If necessary, treatment procedures were rehearsed.

Two weeks later, on day 14, children originally found positive by screening were offered a check by wet combing at the school. Information on the choice of treatment was gathered, but actual application of the treatment was not checked.

One exception in the standardization of the intervention in the three schools was allowed—so as to enhance the informational value of the study. In schools 1 and 3 ‘positive’ was defined as ‘the presence of active infestation’ (living moving lice); in school 2 ‘positive’ was defined as ‘signs of infestation’ (presence of nits, whether or not with living lice), reflecting a no-nit-policy.

The study was approved by the ethics committee of the Ghent University Hospital.

PROCESS AND RESULTS

The populations of the schools were 239, 177 and 261 and all three had a male/female ratio of 1 and a ratio of ethnic minority children (predominantly of Turkish origin) of 1 in 4. An initial meeting was held with the head teachers, the school health departments, and the community organizations (home care, nursing, child health and social welfare) to present the project strategy and to ensure that 20 volunteers would be available for the screening campaign and 10 for home visits.

The idea of a structured approach met with enthusiasm, albeit with scepticism about specific aspects of the project plan (e.g. the feasibility and effectiveness of wet combing). School health departments' participation in the organization of the wet combing screening campaign, considered crucial by the project team, was assured by personal visits after the meeting. All participating volunteers attended a training session, which lasted more than the scheduled 2 hours because of the lively discussions. Among professionals too, misconceptions and prejudices existed (and were not always corrected in one training session).

Of the 677 children in the three schools, 566 (83.4%) were screened by three teams of 5-7 screeners, over 2 to 3 days per school. Table 1 shows the results of the screening campaign.

Table 1.

Results of a wet combing screening campaign in three primary schools

School	Population	Refusals	Absent	Screened	Positive*
1	239	35	26	178	31
2	177	45	13	160	72
3	261	7	26	228	51
Total	677	87	65	566	145

^*In schools 1 and 3 positive defined as presence of living lice or viable nits; in school 2 as signs of past or present infestation

Population prevalence of active infestation (living moving lice) was 13.0% in school 1 and 19.5% in school 3 (without a louse policy in the past). In school 2, the prevalence of signs of active and past infestation (living lice or nits) was 40.7%. In school 1, prevalence was measured separately for Belgian (14.6%) and ethnic-minority children (9.3%) (difference not significant by chi-square test).

The cost of the permanent equipment (wash tubs, towels, magnifying glasses, etc.) for one team of 5-7 volunteers was 500 euro. One volunteer working day of 5 hours was needed to screen 25 children. The cost of consumables (conditioner, combs, etc.) was 10 euro per 25 children. Appropriate accommodation is needed within the school—a well lit, well heated room of sufficient size with a water-resistant floor, water supply and drainage, a waiting room, and the possibility of privacy if requested.

For the 154 ‘positive’ children, 89 home visits (58%) were performed by the sherpas, mostly on day 7. The reasons for not making a house call were refusal (n=31), inability to contact the parents (not at home, not reachable by phone) and failure to keep the appointment (n=34).

Ten families were detected with a long history of louse infestation and relapse, of which five accepted and successfully applied the wet combing technique (after four weeks' treatment, the family was louse-free for six weeks). On day 14 after the initial screening, 85% of the positive children were screened again at the school. Children (or their parents) were asked what treatment option they had chosen (see Table 2). Wet combing was the chosen treatment in 29%, chemical treatment in 19%, and a combination of both in 15%. An array of alternative treatments were used by 6%. 12% said that no treatment had been given (mostly in school 2, where the presence of nits was the definition of ‘positive’). In 19% the treatment option was unknown.

Table 2.

Treatment options chosen in ‘positive’ cases and cure rates at day 14

Method	School 1			School 2*			School 3
	+ve day 0	Checked day 14	Cured day 14	+ve day 0	Checked day 14	Cured day 14	+ve day 0	Checked day 14	Cured day 14
Wet combing	11	11	6	16	16	3	11	11	9
Chemicals	6	6	2	8	8	4	11	11	8
Combinations	4	4	3	4	4	2	11	11	2
Alternatives	3	3	1	0	0	0	5	5	1
None	2	2	1	11	11	2	2	2	1
Unknown	5	4	2	16	16	2	11	6	3
Total	31	30	15	72	55	13	51	46	24

^*In school 2, positive (+ve) was defined as signs of past and present infestation

In schools 1 and 3, where active infestation was the criterion for diagnosis and treatment, 51% of the children were cured at day 14. The likelihood of success was greatest when a single method was consistently applied (15 cured out of 22 positive children treated with wet combing, and 10 cured out of 17 positive children treated with chemicals).

In school 2, where the presence of nits was used as a criterion for infestation, many children were not treated and 76% remained positive by the same criterion.

DISCUSSION

The prevalence of head louse infestation in our study was high. This may be because we selected motivated schools, and motivation may stem from past and present confrontation with head louse epidemics. The use of wet combing as the screening method may also account for the high measured prevalence¹⁰. Another possibility is that the results reflect a worsening trend caused by resistance to chemical treatment¹⁹ or an uncoordinated approach. There was a 17% dropout in the screening campaign. Parents were informed of the campaign a week in advance, and some may have kept their children away from school on the day or checked/treated them beforehand. The principles of informed consent must be respected; also we must accept that some children or parents prefer to keep a diagnosis hidden, do not want to be screened publicly and insist on the privacy of their home.

Nevertheless, we found it feasible and not grossly expensive to organize a wet combing screening campaign with a 83% uptake, followed by a home visit on day 7 for 58% of the positive cases, and follow-up on day 14 for 85% of the positive children. This was possible only because school efforts were backed up by community efforts. We found that parents and organizations were ready to participate as soon as a credible project was presented. To evaluate the feasibility in other districts, one should keep in mind that this project was set up by community workers functioning within healthcare centres in their districts, with a long tradition of network building with all kinds of organizations; this may well have contributed to the success of the intervention.

Further research is needed to decide whether wet screening is cost-effective and whether logistic demands can be diminished by switching to dry combing. The design of the study does not allow statistical comparison of the effectiveness of the different treatments. However, in this study half of the children remained positive whatever the treatment chosen. Perhaps it is necessary to invest more in educational efforts towards caregivers (with training and assistance in the selection and execution of treatment), to provide supportive psychological interventions (targeted at families with long histories of relapse), and to plan human ecology interventions (aimed at building interactions between individual families, schools and community resources).

In this project we suggested wet combing as an alternative to the use of insecticides. Although this approach is not yet evidence-based²⁰, this was the method most often chosen by the parents. In a recent report comparing malathion with wet combing, Roberts et al. conclude that ‘policies advocating bug-busting as first line treatment are inappropriate’²¹. In our opinion, such a conclusion cannot be drawn from their small trial. It was a pragmatic trial, testing effectiveness and not efficacy, since application of the treatment was left to the parents, after a single instruction session. Randomization was within families and not between families, and blinding of allocation to the investigators must have been affected by divergence in the timing of final assessment. Hence, the risk of bias in this small trial is high. Furthermore, effectiveness testing in normal practice conditions should follow and not precede efficacy testing under optimal conditions.

Our results indicate that both physical and chemical treatments of head lice are of low effectiveness. Further research on this common condition is required.