title: Experimental hut evaluation of linalool spatial repellent agar gel against Anopheles gambiae sensu stricto mosquitoes in a semi-field system in Bagamoyo, Tanzania.
abstract: BACKGROUND
  Malaria vector control is in need of new tools to face its current challenges such as the spread of pyrethroid-resistance and the increase of outdoor feeding mosquitoes. New strategies such as spatial repellents need to be evaluated as supplemental tools to existing control measures such as insecticide treated bed nets and indoor residual spraying. Linalool is a naturally occurring terpene alcohol commonly found in flowers and spices with reportedly repellent properties.
  
  
  METHODS
  Four experimental huts fitted with exit traps and enclosed inside a large screened semi-field system were used for the evaluation. The tested spatial repellent product consisted of an agar gel emanator containing 73% linalool. Two rounds of experiments using a Latin square design were conducted to evaluate the efficacy of the linalool emanators compared to no treatment (negative control) and a transfluthrin coil (positive) against lab-reared disease free Anopheles gambiae s.s.. The emanators were hung inside experimental huts where two volunteers were sleeping unprotected. The outcome measures were repellency, % feeding inhibition, %mortality and post 24 h % mortality.
  
  
  RESULTS
  Unlike the mosquito coil, the linalool emanators did not show any feeding inhibition, repellency or induced mortality compared to the negative control. On the other hand mosquitoes kept for 24 h post exposure were 3 times more likely to die after being exposed to two 73% linalool emanators than the negative control.
  
  
  CONCLUSIONS
  Our results indicate that linalool agar gel emanators are not adequate as a spatial repellent against Anopheles gambiae s.s.. However adding linalool to known repellent formulations could be advantageous, not only because of its pleasant scent but also because of the delayed mortality effect it has on mosquitoes.
authors.affiliation: Ifakara Health Institute, Intervention and Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania. mmohamed@ihi.or.tz.
authors.forename: Mgeni Mohamed
authors.initials: MM
authors.lastname: Tambwe
authors.affiliation: Ifakara Health Institute, Intervention and Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania. embeyela@gmail.com.
authors.forename: Edgar Mtaki
authors.initials: EM
authors.lastname: Mbeyela
authors.affiliation: Ifakara Health Institute, Intervention and Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania. bmassinda@gmail.com.
authors.forename: Brian Migamyo
authors.initials: BM
authors.lastname: Massinda
authors.affiliation: Ifakara Health Institute, Intervention and Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania. smoore@ihi.or.tz.|Swiss Tropical & Public Health Institute, Soccinstraße 57, 4002, Basel, Switzerland. smoore@ihi.or.tz.|University of Basel, Petersplatz 1, 4003, Basel, Switzerland. smoore@ihi.or.tz.
authors.forename: Sarah Jane
authors.initials: SJ
authors.lastname: Moore
authors.affiliation: Ifakara Health Institute, Intervention and Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania. mmaia@ihi.or.tz.|Swiss Tropical & Public Health Institute, Soccinstraße 57, 4002, Basel, Switzerland. mmaia@ihi.or.tz.|University of Basel, Petersplatz 1, 4003, Basel, Switzerland. mmaia@ihi.or.tz.
authors.forename: Marta Ferreira
authors.initials: MF
authors.lastname: Maia
mesh_terms: D000080462:Acyclic Monoterpenes; D000362:Agar; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D003521:Cyclopropanes / Q000737:chemistry / Q000494:pharmacology; D005247:Feeding Behavior; D005260:Female; D005464:Fluorobenzenes / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007302:Insect Repellents / Q000737:chemistry / Q000494:pharmacology*; D008288:Malaria / Q000517:prevention & control / Q000635:transmission; D039821:Monoterpenes / Q000737:chemistry / Q000494:pharmacology*; D013636:Tanzania
chemical_list: D000080462:Acyclic Monoterpenes; D003521:Cyclopropanes; D005464:Fluorobenzenes; D007302:Insect Repellents; D039821:Monoterpenes; D000362:Agar; C018584:linalool; C560613:transfluthrin