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document
Entomological determinants of insecticide-treated bed net effectiveness in Western Myanmar . 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 . FINDINGS 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 .
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Intervention_Pharmacological
insecticide-treated bed nets ( ITN )
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Intervention_Pharmacological
ITN
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Intervention_Pharmacological
ITN
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Intervention_Surgical
salivary glands were dissected
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Intervention_Physical
microscopy
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Intervention_Pharmacological
ITN
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Intervention_Pharmacological
ITN
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Outcome_Other
effectiveness
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Outcome_Other
protective effect
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Outcome_Other
malaria vector abundance and biting behaviour
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Outcome_Mental
human population sleeping habits
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Outcome_Other
potential malaria vector species
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Outcome_Other
biting habits .
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Outcome_Other
preference
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Outcome_Physical
outdoor biting
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Outcome_Other
;
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Outcome_Other
human biting
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Outcome_Other
peak biting time
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Outcome_Other
bites recorded
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Outcome_Other
proportion of children
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Outcome_Mental
sleeping
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Outcome_Physical
malaria sporozoites
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Outcome_Physical
Peak vector biting
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Outcome_Other
efficacy
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Participant_Sample-size
4,824
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Participant_Sex
female
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Participant_Sample-size
916 person
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Participant_Age
children