title: Transmission blocking activity of Azadirachta indica and Guiera senegalensis extracts on the sporogonic development of Plasmodium falciparum field isolates in Anopheles coluzzii mosquitoes.
abstract: BACKGROUND
  Targeting the stages of the malaria parasites responsible for transmission from the human host to the mosquito vector is a key pharmacological strategy for malaria control. Research efforts to identify compounds that are active against these stages have significantly increased in recent years. However, at present, only two drugs are available, namely primaquine and artesunate, which reportedly act on late stage gametocytes.
  
  
  METHODS
  In this study, we assessed the antiplasmodial effects of 5 extracts obtained from the neem tree Azadirachta indica and Guiera senegalensis against the early vector stages of Plasmodium falciparum, using field isolates. In an ex vivo assay gametocytaemic blood was supplemented with the plant extracts and offered to Anopheles coluzzii females by membrane feeding. Transmission blocking activity was evaluated by assessing oocyst prevalence and density on the mosquito midguts.
  
  
  RESULTS
  Initial screening of the 5 plant extracts at 250 ppm revealed transmission blocking activity in two neem preparations. Up to a concentration of 70 ppm the commercial extract NeemAzal completely blocked transmission and at 60 ppm mosquitoes of 4 out of 5 replicate groups remained uninfected. Mosquitoes fed on the ethyl acetate phase of neem leaves at 250 ppm showed a reduction in oocyst prevalence of 59.0% (CI₉₅ 12.0 - 79.0; p < 10-4) and in oocyst density of 90.5% (CI₉₅ 86.0 - 93.5; p < 10-4 ), while the ethanol extract from the same plant part did not exhibit any activity. No evidence of transmission blocking activity was found using G. senegalensis ethyl acetate extract from stem galls.
  
  
  CONCLUSIONS
  The results of this study highlight the potential of antimalarial plants for the discovery of novel transmission blocking molecules, and open up the potential of developing standardized transmission blocking herbal formulations as malaria control tools to complement currently used antimalarial drugs and combination treatments.
authors.affiliation: Institut de Recherche en Sciences de la Santé, 01 BP545 Bobo Dioulasso, Burkina Faso. yrserge@yahoo.fr.
authors.forename: Rakiswendé S
authors.initials: RS
authors.lastname: Yerbanga
authors.forename: Leonardo
authors.initials: L
authors.lastname: Lucantoni
authors.forename: Robert K
authors.initials: RK
authors.lastname: Ouédraogo
authors.forename: Dari F
authors.initials: DF
authors.lastname: Da
authors.forename: Franck A
authors.initials: FA
authors.lastname: Yao
authors.forename: Koudraogo B
authors.initials: KB
authors.lastname: Yaméogo
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Churcher
authors.forename: Giulio
authors.initials: G
authors.lastname: Lupidi
authors.forename: Orazio
authors.initials: O
authors.lastname: Taglialatela-Scafati
authors.forename: Louis Clément
authors.initials: LC
authors.lastname: Gouagna
authors.forename: Anna
authors.initials: A
authors.lastname: Cohuet
authors.forename: George K
authors.initials: GK
authors.lastname: Christophides
authors.forename: Jean Bosco
authors.initials: JB
authors.lastname: Ouédraogo
authors.forename: Annette
authors.initials: A
authors.lastname: Habluetzel
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology*; D031601:Azadirachta / Q000737:chemistry*; D002675:Child, Preschool; D029764:Combretaceae / Q000737:chemistry*; D005260:Female; D006801:Humans; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D010963:Plasmodium falciparum / Q000187:drug effects*
chemical_list: D010936:Plant Extracts
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