title: Vector competence of Aedes vexans (Meigen), Culex poicilipes (Theobald) and Cx. quinquefasciatus Say from Senegal for West and East African lineages of Rift Valley fever virus.
abstract: BACKGROUND
  Rift Valley fever virus (RVFV; Phlebovirus, Bunyaviridae) is a mosquito-borne, zoonotic pathogen. In Senegal, RVFV was first isolated in 1974 from Aedes dalzieli (Theobald) and thereafter from Ae. fowleri (de Charmoy), Ae. ochraceus Theobald, Ae. vexans (Meigen), Culex poicilipes (Theobald), Mansonia africana (Theobald) and Ma. uniformis (Theobald). However, the vector competence of these local species has never been demonstrated making hypothetical the transmission cycle proposed for West Africa based on serological data and mosquito isolates.
  
  
  METHODS
  Aedes vexans and Cx. poicilipes, two common mosquito species most frequently associated with RVFV in Senegal, and Cx. quinquefasciatus, the most common domestic species, were assessed after oral feeding with three RVFV strains of the West and East/central African lineages. Fully engorged mosquitoes (420 Ae. vexans, 563 Cx. quinquefasciatus and 380 Cx. poicilipes) were maintained at 27 ± 1 °C and 70-80% relative humidity. The saliva, legs/wings and bodies were tested individually for the RVFV genome using real-time RT-PCR at 5, 10, 15 and 20 days post exposure (dpe) to estimate the infection, dissemination, and transmission rates. Genotypic characterisation of the 3 strains used were performed to identify factors underlying the different patterns of transmission.
  
  
  RESULTS
  The infection rates varied between 30.0-85.0% for Ae. vexans, 3.3-27% for Cx. quinquefasciatus and 8.3-46.7% for Cx. poicilipes, and the dissemination rates varied between 10.5-37% for Ae. vexans, 9.5-28.6% for Cx. quinquefasciatus and 3.0-40.9% for Cx. poicilipes. However only the East African lineage was transmitted, with transmission rates varying between 13.3-33.3% in Ae. vexans, 50% in Cx. quinquefasciatus and 11.1% in Cx. poicilipes. Culex mosquitoes were less susceptible to infection than Ae. vexans. Compared to other strains, amino acid variation in the NSs M segment proteins of the East African RVFV lineage human-derived strain SH172805, might explain the differences in transmission potential.
  
  
  CONCLUSIONS
  Our findings revealed that all the species tested were competent for RVFV with a significant more important role of Ae. vexans compared to Culex species and a highest potential of the East African lineage to be transmitted.
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. elndiaye@pasteur.sn.|Université Cheikh Anta Diop de Dakar, Département de Biologie Animale, Faculté des Sciences et Techniques, Dakar, Senegal. elndiaye@pasteur.sn.
authors.forename: El Hadji
authors.initials: el H
authors.lastname: Ndiaye
authors.affiliation: Institut Pasteur de Dakar, Unité des Arbovirus et Virus de Fièvres hémorragiques, Dakar, Senegal. gamou.fall@pasteur.sn.
authors.forename: Gamou
authors.initials: G
authors.lastname: Fall
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. agaye@pasteur.sn.|Université Cheikh Anta Diop de Dakar, Département de Biologie Animale, Faculté des Sciences et Techniques, Dakar, Senegal. agaye@pasteur.sn.
authors.forename: Alioune
authors.initials: A
authors.lastname: Gaye
authors.affiliation: Institut Pasteur de Dakar, Unité des Arbovirus et Virus de Fièvres hémorragiques, Dakar, Senegal. nsbob@pasteur.sn.
authors.forename: Ndeye Sakha
authors.initials: NS
authors.lastname: Bob
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. ctalla@pasteur.sn.
authors.forename: Cheikh
authors.initials: C
authors.lastname: Talla
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. ctdiagne@pasteur.sn.|Université Cheikh Anta Diop de Dakar, Département de Biologie Animale, Faculté des Sciences et Techniques, Dakar, Senegal. ctdiagne@pasteur.sn.
authors.forename: Cheikh Tidiane
authors.initials: CT
authors.lastname: Diagne
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. ddiallo@pasteur.sn.
authors.forename: Diawo
authors.initials: D
authors.lastname: Diallo
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. ba@pasteur.sn.
authors.forename: Yamar
authors.initials: Y
authors.lastname: B A
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. dia@pasteur.sn.
authors.forename: Ibrahima
authors.initials: I
authors.lastname: Dia
authors.affiliation: MRC-University of Glasgow Centre for Virus Research, Glasgow, G61 1QH, Scotland, UK. alain.kohl@glasgow.ac.uk.
authors.forename: Alain
authors.initials: A
authors.lastname: Kohl
authors.affiliation: Institut Pasteur de Dakar, Unité des Arbovirus et Virus de Fièvres hémorragiques, Dakar, Senegal. asall@pasteur.sn.
authors.forename: Amadou Alpha
authors.initials: AA
authors.lastname: Sall
authors.affiliation: Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal. diallo@pasteur.sn.
authors.forename: Mawlouth
authors.initials: M
authors.lastname: Diallo
mesh_terms: D000330:Aedes / Q000821:virology*; D000825:Animal Structures / Q000821:virology; D000818:Animals; D003465:Culex / Q000821:virology*; D007303:Insect Vectors; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012296:Rift Valley fever virus / Q000302:isolation & purification*; D012463:Saliva / Q000821:virology; D012675:Senegal