First field evidence for natural vertical transmission of West Nile virus in Culex univittatus complex mosquitoes from Rift Valley province, Kenya

• Published in: The American journal of tropical medicine and hygiene Vol. 62; no. 2; pp. 240 - 246
• Main Authors: Miller, BR, Nasci, RS, Godsey, MS, Savage, HM, Lutwama, JJ, Lanciotti, RS, Peters, CJ
• Format: Journal Article
• Language: English
• Published: Lawrence, KS ASTMH 01.02.2000; Allen Press
• Subjects: Amino Acid Sequence; Animals; Antigens, Viral - analysis; Arboviral encephalitis; Arboviroses; Base Sequence; Biological and medical sciences; Brackish; Cercopithecus aethiops; Culex - virology; Culex pipiens; Culex univittatus; Culicidae; DNA Primers - chemistry; DNA, Viral - chemistry; Electrophoresis, Agar Gel; Female; Flavivirus; Fluorescent Antibody Technique, Indirect; Freshwater; Fundamental and applied biological sciences. Psychology; Human viral diseases; Humans; Infectious Disease Transmission, Vertical; Infectious diseases; Insect Vectors - virology; Kenya; Kenya - epidemiology; Medical sciences; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Molecular Sequence Data; Phylogeny; Reverse Transcriptase Polymerase Chain Reaction; RNA, Viral - chemistry; RNA, Viral - isolation & purification; Romania; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Tropical medicine; Tropical viral diseases; Vectors. Intermediate hosts; Vero Cells; Viral diseases; Viral Envelope Proteins - chemistry; Viral Envelope Proteins - genetics; West Nile Fever - epidemiology; West Nile Fever - immunology; West Nile Fever - transmission; West Nile Fever - virology; West Nile virus; West Nile virus - classification; West Nile virus - genetics; West Nile virus - immunology; Kenya; Africa; Insecta; Phylogenetic tree; Flavivirus; Virus; Arthropoda; West Nile virus; Culicidae; Vertical transmission; Japanese encephalitis group virus; Flaviviridae; Invertebrata; Vector; Diptera
• ISSN: 0002-9637; 1476-1645
• DOI: 10.4269/ajtmh.2000.62.240

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.