title: 'A bite before bed': exposure to malaria vectors outside the times of net use in the highlands of western Kenya.
abstract: BACKGROUND
  The human population in the highlands of Nyanza Province, western Kenya, is subject to sporadic epidemics of Plasmodium falciparum. Indoor residual spraying (IRS) and long-lasting insecticide treated nets (LLINs) are used widely in this area. These interventions are most effective when Anopheles rest and feed indoors and when biting occurs at times when individuals use LLINs. It is therefore important to test the current assumption of vector feeding preferences, and late night feeding times, in order to estimate the extent to which LLINs protect the inhabitants from vector bites.
  
  
  METHODS
  Mosquito collections were made for six consecutive nights each month between June 2011 and May 2012. CDC light-traps were set next to occupied LLINs inside and outside randomly selected houses and emptied hourly. The net usage of residents, their hours of house entry and exit and times of sleeping were recorded and the individual hourly exposure to vectors indoors and outdoors was calculated. Using these data, the true protective efficacy of nets (P*), for this population was estimated, and compared between genders, age groups and from month to month.
  
  
  RESULTS
  Primary vector species (Anopheles funestus s.l. and Anopheles arabiensis) were more likely to feed indoors but the secondary vector Anopheles coustani demonstrated exophagic behaviour (p < 0.05). A rise in vector biting activity was recorded at 19:30 outdoors and 18:30 indoors. Individuals using LLINs experienced a moderate reduction in their overall exposure to malaria vectors from 1.3 to 0.47 bites per night. The P* for the population over the study period was calculated as 51% and varied significantly with age and season (p < 0.01).
  
  
  CONCLUSIONS
  In the present study, LLINs offered the local population partial protection against malaria vector bites. It is likely that P* would be estimated to be greater if the overall suppression of the local vector population due to widespread community net use could be taken into account. However, the overlap of early biting habit of vectors and human activity in this region indicates that additional methods of vector control are required to limit transmission. Regular surveillance of both vector behaviour and domestic human-behaviour patterns would assist the planning of future control interventions in this region.
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK. cookemk7@gmail.com.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Cooke
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. kahindisamuel@gmail.com.
authors.forename: Sam C
authors.initials: SC
authors.lastname: Kahindi
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. robin.migiro@rocketmail.com.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Oriango
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. cowaga@gmail.com.
authors.forename: Chrispin
authors.initials: C
authors.lastname: Owaga
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. eayoma@kemricdc.org.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ayoma
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. mabukadan@gmail.com.
authors.forename: Danspaid
authors.initials: D
authors.lastname: Mabuka
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. finddenis@yahoo.com.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nyangau
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. lucycayth@gmail.com.
authors.forename: Lucy
authors.initials: L
authors.lastname: Abel
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. lizmalinaelizabeth@yahoo.com.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Atieno
authors.affiliation: Kenya Medical Research Institute Centre for Global Health Research/Centers for Disease Control and Prevention, Kisumu, Kenya. stephenawuor@yahoo.com.
authors.forename: Stephen
authors.initials: S
authors.lastname: Awuor
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK. chris.drakeley@lshtm.ac.uk.
authors.forename: Chris
authors.initials: C
authors.lastname: Drakeley
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK. jonathan.cox@lshtm.ac.uk.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cox
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK. jennyc.stevenson@macharesearch.org.|Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health/Macha Research Trust, Choma, Zambia. jennyc.stevenson@macharesearch.org.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Stevenson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000852:Anopheles / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007299:Insect Bites and Stings / Q000453:epidemiology* / Q000209:etiology; D007303:Insect Vectors / Q000502:physiology*; D057148:Insecticide-Treated Bednets; D007630:Kenya / Q000453:epidemiology; D008288:Malaria / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D008875:Middle Aged; D009032:Mosquito Control / Q000379:methods*; D012621:Seasons; D055815:Young Adult