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Zika virus in Gabon (Central Africa)--2007: a new threat from Aedes albopictus? - PubMed

  • ️Wed Jan 01 2014

Zika virus in Gabon (Central Africa)--2007: a new threat from Aedes albopictus?

Gilda Grard et al. PLoS Negl Trop Dis. 2014.

Abstract

Background: Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses.

Methodology/principal findings: Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). The ratio of Aedes albopictus pools positive for ZIKV was similar to that positive for dengue virus during the concomitant dengue outbreak suggesting similar mosquito infection rates and, presumably, underlying a human ZIKV outbreak. ZIKV sequences from the envelope and NS3 genes were amplified from a human serum sample. Phylogenetic analysis placed the Gabonese ZIKV at a basal position in the African lineage, pointing to ancestral genetic diversification and spread.

Conclusions/significance: We provide the first direct evidence of human ZIKV infections in Gabon, and its first occurrence in the Asian tiger mosquito, Aedes albopictus. These data reveal an unusual natural life cycle for this virus, occurring in an urban environment, and potentially representing a new emerging threat due to this novel association with a highly invasive vector whose geographic range is still expanding across the globe.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Geographic distribution of Zika and chikungunya and/or dengue viruses infections in Gabon in 2007.

The left-hand panel indicates Gabonese CHIKV and/or DENV cases in green circles and ZIKV cases in purple circles. The right-hand panel shows the location of Libreville suburbs where ZIKV-positive human sera (H) and mosquito pools (M) were detected.

Figure 2
Figure 2. Phylogenetic relationships between concatenated sequences of the Zika virus envelope and NS3 genes.

The tree was constructed with the maximum likelihood algorithm implemented in PhyML and rooted on midpoint. Bootstrap values are shown at the respective nodes, followed by bootstrap values resulting from NJ analysis and, finally, the posterior probability resulting from Bayesian analysis. The scale bar indicates the number of substitutions per site. The GenBank accession numbers for the 2007 Gabonese ZIKV isolate are KF270886 (envelope) and KF270887 (NS3).

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Grants and funding

This work was supported by CIRMF, which is funded by the Gabonese Government, Total Gabon and the French Foreign Ministry. It was also partially financed by grants from Fondation Christophe et Rodolphe Mérieux, Institut de France, Institut de recherches pour le développement (IRD),and Metabiota. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.