Abstract
BackgroundWest Nile virus (WNV) has a wide geographical distribution and has been associated to cause neurological disease in humans and horses. Mosquitoes are the traditional vectors for WNV; however, the virus has also been isolated from tick species in North Africa and Europe which could be a means of introduction and spread of the virus over long distances through migratory birds. Although WNV has been isolated in mosquitoes in Kenya, paucity of genetic and pathogenicity data exists. We previously reported the isolation of WNV from ticks collected from livestock and wildlife in Ijara District of Kenya, a hotspot for arbovirus activity. Here we report the full genome sequence and phylogenetic investigation of their origin and relation to strains from other regions.MethodsA total of 10,488 ticks were sampled from animal hosts, classified to species and processed in pools of up to eight ticks per pool. Virus screening was performed by cell culture, RT-PCR and sequencing. Phylogenetic analysis was carried out to determine the evolutionary relationships of our isolate.ResultsAmong other viruses, WNV was isolated from a pool of Rhipicephalus pulchellus sampled from cattle, sequenced and submitted to GenBank (Accession number: KC243146). Comparative analysis with 27 different strains revealed that our isolate belongs to lineage 1 and clustered relatively closely to isolates from North Africa and Europe, Russia and the United States. Overall, Bayesian analysis based on nucleotide sequences showed that lineage 1 strains including the Kenyan strain had diverged 200 years ago from lineage 2 strains of southern Africa. Ijara strain collected from a tick sampled on livestock was closest to another Kenyan strain and had diverged 20 years ago from strains detected in Morocco and Europe and 30 years ago from strains identified in the USA.ConclusionTo our knowledge, this is the first characterized WNV strain isolated from R. pulchellus. The epidemiological role of this tick in WNV transmission and dissemination remains equivocal but presents tick verses mosquito virus transmission has been neglected. Genetic data of this strain suggest that lineage 1 strains from Africa could be dispersed through tick vectors by wild migratory birds to Europe and beyond.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-014-0542-2) contains supplementary material, which is available to authorized users.
Highlights
West Nile virus (WNV) has a wide geographical distribution and has been associated to cause neurological disease in humans and horses
WNV screening in ticks collected from various animal hosts in Ijara District, Kenya, resulted in two tick-borne isolates obtained from R. pulchellus sampled from cattle and warthog as described in
These isolates were confirmed to be WNV after being subjected to PCR testing and subsequent sequencing. These WNV isolates were subjected to Sanger sequencing of the non-structural protein 5 (NS5) gene region used for identification and confirmed to be WNV
Summary
West Nile virus (WNV) has a wide geographical distribution and has been associated to cause neurological disease in humans and horses. Vector competence studies performed mainly on soft ticks such as Argas persicus, A. hermanni [17] and Ornithodoros moubata [15] indicate the potential role of ticks in WNV transmission. WNV causes mainly mild febrile illness but can result in meningo-encephalitis, acute paralysis and death in severe cases in humans and horses [7,18,19,20,21,22]. The proportion of elderly patients presenting with severe neurologic illness due to WNV has been reported to be high in the USA [23,24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
