Head lice predictors and infestation dynamics among primary school children in Norway.
BACKGROUND
Health providers need to know which measures to take and children to prioritize in order to decrease costs associated with head lice infestations.


OBJECTIVE
Our aim was to determine the most important predictors for head lice and identify the major drivers of an infestation outbreak in a low-prevalence area.


METHODS
The study was based on three datasets of head lice prevalence (retrospective, point prevalence and prospective approach) from primary school children (ages 6-12) at 12 schools in Oslo, Norway. The tested predictors were siblings with lice, individual and household characteristics as well as class and school affiliation. Self-reported monthly incidences (prospective approach) of head lice were used to evaluate infestation dynamics.


RESULTS
Infested siblings strongly increased the odds of head lice infestation of school children (odds ratio 36, 26 and 7 in the three datasets) whereas having short hair halved the odds. Household characteristics were of minor importance, and class affiliation proved more important than school affiliation. Having head lice in one school term increased the odds of an infestation in the next, but this effect diminished over time. About 97% of all self-reported infestations were noted in two consecutive months or less.


CONCLUSIONS
With the exception of hair length, we have found that individual and household characteristics are of minor importance to predict head lice infestations in a low-prevalence country and that unnoticed transmissions in school classes and families are likely to be the major driver upon outbreaks.
Department of Ecology and Natural resource management, Norwegian University of Life Sciences, PO Box 5003, NO 1432 ÅS.
Tone
T
Birkemoe
Department of Pest Control, Norwegian Institute of Public Health.
Heidi Heggen
HH
Lindstedt
Department of Pest Control, Norwegian Institute of Public Health.
Preben
P
Ottesen
Department of Pest Control, Norwegian Institute of Public Health.
Arnulf
A
Soleng
Division of Epidemiology, Norwegian Institute of Public Health and Institute of Health and Society, University of Oslo, Oslo, Norway.
Øyvind
Ø
Næss
Department of Pest Control, Norwegian Institute of Public Health, bjorn.arne.rukke@fhi.no.
Bjørn Arne
BA
Rukke
D000818:Animals; D002648:Child; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D015994:Incidence; D010373:Lice Infestations / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D055361:Multilevel Analysis; D009664:Norway / Q000453:epidemiology; D016017:Odds Ratio; D010374:Pediculus; D010379:Peer Group; D015995:Prevalence; D011446:Prospective Studies; D012189:Retrospective Studies; D012307:Risk Factors; D012536:Scalp Dermatoses / Q000453:epidemiology*; D012574:Schools; D035781:Siblings; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires
Multilevel analysis; pediculosis; population dynamics; prevalence; schools; socio-economic factors.