title: First field evidence for natural vertical transmission of West Nile virus in Culex univittatus complex mosquitoes from Rift Valley province, Kenya.
abstract: West Nile virus is a mosquito borne flavivirus endemic over a large geographic area including Africa, Asia, and the Middle East. Although the virus generally causes a mild, self-limiting febrile illness in humans, it has sporadically caused central nervous system infections during epidemics. An isolate of West Nile virus was obtained from a pool of four male Culex univittatus complex mosquitoes while we were conducting an investigation of Rift Valley fever along the Kenya-Uganda border in February-March 1998. This represents the first field isolation of West Nile virus from male mosquitoes and strongly suggests that vertical transmission of the virus occurs in the primary maintenance mosquito vector in Kenya. A phylogenetic analysis of the complete amino acid sequence of the viral envelope glycoprotein demonstrated a sister relationship with a Culex pipiens mosquito isolate from Romania made in 1996. This unexpected finding probably reflects the role of migratory birds in disseminating West Nile virus between Africa and Europe.
authors.affiliation: Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 80522-2087, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Miller
authors.forename: R S
authors.initials: RS
authors.lastname: Nasci
authors.forename: M S
authors.initials: MS
authors.lastname: Godsey
authors.forename: H M
authors.initials: HM
authors.lastname: Savage
authors.forename: J J
authors.initials: JJ
authors.lastname: Lutwama
authors.forename: R S
authors.initials: RS
authors.lastname: Lanciotti
authors.forename: C J
authors.initials: CJ
authors.lastname: Peters
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D001483:Base Sequence; D002522:Chlorocebus aethiops; D003465:Culex / Q000821:virology*; D017931:DNA Primers / Q000737:chemistry; D004279:DNA, Viral / Q000737:chemistry; D004587:Electrophoresis, Agar Gel; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D018445:Infectious Disease Transmission, Vertical; D007303:Insect Vectors / Q000821:virology*; D007630:Kenya / Q000453:epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012367:RNA, Viral / Q000737:chemistry / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics; D014901:West Nile Fever / Q000453:epidemiology / Q000276:immunology / Q000635:transmission* / Q000821:virology; D014902:West Nile virus / Q000145:classification / Q000235:genetics / Q000276:immunology*
chemical_list: D000956:Antigens, Viral; D017931:DNA Primers; D004279:DNA, Viral; D012367:RNA, Viral; D014759:Viral Envelope Proteins