Do some families act as a reservoir of head lice in the community? Surveys for prevalence and insecticide resistance suggest this is the case.

In response to increasing complaints of head louse infestation in the area of Cambridge, UK, in the mid-1990s, a series of prevalence surveys in selected schools coupled with collection of lice were commissioned by the local health authority. Carers of infested children were provided with advice on treatment by school nurses. Lice collected during these surveys were tested in the laboratory for evidence of resistance to insecticides. These data were used by the health authority to make decisions about recommended insecticide use for control of head infestations. Surveys over 3 years 1995-1997 found increasing prevalence of lice and increasing resistance to pyrethroids and malathion insecticides across the city. In two selected linked schools, the school nurse initiated a series of workshops and demonstrations to encourage families to treat by wet combing with conditioner in line with government recommendations and local general practitioner advice. Surveys conducted before and after the combing initiative found that prevalence increased in one school and was effectively unchanged in the other. Data collected in 1996 and 1997 from two schools showed that some families were continuously infested across 2 years and would act as a reservoir of infestation for the rest of the community.