title: Do topical repellents divert mosquitoes within a community? Health equity implications of topical repellents as a mosquito bite prevention tool.
abstract: OBJECTIVE
  Repellents do not kill mosquitoes--they simply reduce human-vector contact. Thus it is possible that individuals who do not use repellents but dwell close to repellent users experience more bites than otherwise. The objective of this study was to measure if diversion occurs from households that use repellents to those that do not use repellents.
  
  
  METHODS
  The study was performed in three Tanzanian villages using 15%-DEET and placebo lotions. All households were given LLINs. Three coverage scenarios were investigated: complete coverage (all households were given 15%-DEET), incomplete coverage (80% of households were given 15%-DEET and 20% placebo) and no coverage (all households were given placebo). A crossover study design was used and coverage scenarios were rotated weekly over a period of ten weeks. The placebo lotion was randomly allocated to households in the incomplete coverage scenario. The level of compliance was reported to be close to 100%. Mosquito densities were measured through aspiration of resting mosquitoes. Data were analysed using negative binomial regression models.
  
  
  RESULTS
  Repellent-users had consistently fewer mosquitoes in their dwellings. In villages where everybody had been given 15%-DEET, resting mosquito densities were fewer than half that of households in the no coverage scenario (Incidence Rate Ratio [IRR]=0.39 (95% confidence interval [CI]: 0.25-0.60); p<0.001). Placebo-users living in a village where 80% of the households used 15%-DEET were likely to have over four-times more mosquitoes (IRR=4.17; 95% CI: 3.08-5.65; p<0.001) resting in their dwellings in comparison to households in a village where nobody uses repellent.
  
  
  CONCLUSIONS
  There is evidence that high coverage of repellent use could significantly reduce man-vector contact but with incomplete coverage evidence suggests that mosquitoes are diverted from households that use repellent to those that do not. Therefore, if repellents are to be considered for vector control, strategies to maximise coverage are required.
authors.affiliation: Swiss Tropical & Public Health Institute, Department of Epidemiology & Public Health, Basel, Switzerland ; University of Basel, Basel, Switzerland ; Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Bagamoyo, Pwani Region, United Republic of Tanzania.
authors.forename: Marta Ferreira
authors.initials: MF
authors.lastname: Maia
authors.affiliation: Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Bagamoyo, Pwani Region, United Republic of Tanzania ; London School of Hygiene & Tropical Medicine, Department of Disease Control, London, England, United Kingdom.
authors.forename: Sangoro Peter
authors.initials: SP
authors.lastname: Onyango
authors.affiliation: Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Bagamoyo, Pwani Region, United Republic of Tanzania.
authors.forename: Max
authors.initials: M
authors.lastname: Thele
authors.affiliation: Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Bagamoyo, Pwani Region, United Republic of Tanzania.
authors.forename: Emmanuel Titus
authors.initials: ET
authors.lastname: Simfukwe
authors.affiliation: Duke University, Department of Biostatistics and Bioinformatics, Durham, North Carolina, United States of America ; Duke University, Duke Global Health Institute, Durham, North Carolina, United States of America.
authors.forename: Elizabeth Louise
authors.initials: EL
authors.lastname: Turner
authors.affiliation: Swiss Tropical & Public Health Institute, Department of Epidemiology & Public Health, Basel, Switzerland ; University of Basel, Basel, Switzerland ; Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Bagamoyo, Pwani Region, United Republic of Tanzania.
authors.forename: Sarah Jane
authors.initials: SJ
authors.lastname: Moore
mesh_terms: D000818:Animals; D009033:Culicidae / Q000187:drug effects* / Q000502:physiology; D003671:DEET; D006801:Humans; D007299:Insect Bites and Stings / Q000453:epidemiology* / Q000517:prevention & control*; D007302:Insect Repellents / Q000009:adverse effects*; D011156:Population Density; D012044:Regression Analysis; D013636:Tanzania / Q000453:epidemiology
chemical_list: D007302:Insect Repellents; D003671:DEET