title: Entomological determinants of insecticide-treated bed net effectiveness in Western Myanmar.
abstract: BACKGROUND
  In a large cluster randomized control trial of insecticide-treated bed nets (ITN) in Western Myanmar the malaria protective effect of ITN was found to be highly variable and, in aggregate, the effect was not statistically significant. A coincident entomological investigation measured malaria vector abundance and biting behaviour and the human population sleeping habits, factors relevant to ITN effectiveness.
  
  
  METHODS
  Entomological surveys were carried out using different catching methods to identify potential malaria vector species and characterise their biting habits. The salivary glands were dissected from all female anophelines caught to identify sporozoites by microscopy.
  
  
  RESULTS
  Between 1995 and 2000 a total of 4,824 female anopheline mosquitoes were caught with various catching methods. A total of 916 person nights yielded 3,009 female anopheline mosquitoes between 6 pm and 6 am. Except for Anopheles annularis, which showed no apparent preference (51% outdoor biting), all major species showed a strong preference for outdoor biting; Anopheles epiroticus (79%), Anopheles subpictus (72%), Anopheles maculatus (92%), Anopheles aconitus (85%) and Anopheles vagus (72%). Most human biting occurred in the early evening with the peak biting time between 6 pm and 7 pm (35%). Overall 51% (1447/2837) of all bites recorded were between 6 pm and 8 pm. A large proportion of children were not sleeping under an ITN during peak biting times. Only one An. annularis mosquito (0.02%) had malaria sporozoites identified in the salivary glands.
  
  
  CONCLUSIONS
  Peak vector biting occurred early in the evening and mainly occurred outdoors. The limited efficacy of ITN in this area of Western Myanmar may be explained by the biting behaviour of the prevalent Anopheles mosquito vectors in this area.
authors.affiliation: Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Faculty of Tropical Medicine, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Rajvithi Rd,, Ratchathewi District, Bangkok 10400, Thailand. nickw@tropmedres.ac.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Smithuis
authors.forename: Moe Kyaw
authors.initials: MK
authors.lastname: Kyaw
authors.forename: U Ohn
authors.initials: UO
authors.lastname: Phe
authors.forename: Ingrid
authors.initials: I
authors.lastname: van der Broek
authors.forename: Nina
authors.initials: N
authors.lastname: Katterman
authors.forename: Colin
authors.initials: C
authors.lastname: Rogers
authors.forename: Patrick
authors.initials: P
authors.lastname: Almeida
authors.forename: Piet A
authors.initials: PA
authors.lastname: Kager
authors.forename: Kasia
authors.initials: K
authors.lastname: Stepniewska
authors.forename: Yoel
authors.initials: Y
authors.lastname: Lubell
authors.forename: Julie A
authors.initials: JA
authors.lastname: Simpson
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: White
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D008288:Malaria / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008853:Microscopy; D009032:Mosquito Control / Q000379:methods*; D002052:Myanmar / Q000453:epidemiology; D010961:Plasmodium / Q000302:isolation & purification; D012469:Salivary Glands / Q000469:parasitology