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Population genetics of two key mosquito vectors of Rift Valley Fever virus reveals new insights into the changing disease outbreak patterns in Kenya.

Tchouassi DP, Bastos AD, Sole CL, Diallo M, Lutomiah J, Mutisya J, Mulwa F, Borgemeister C, Sang R, Torto B - PLoS Negl Trop Dis (2014)

Bottom Line: Our data strongly suggest that unlike Ae. mcintoshi, Ae. ochraceus appears to be a relatively recent, single 'introduction' into Kenya.These results, together with increasing isolations from this vector, indicate that Ae. ochraceus will likely be of greater epidemiological importance in future RVF outbreaks in Kenya.Furthermore, the overall vector complexity calls into question the feasibility of mosquito population control approaches reliant on genetic modification.

View Article: PubMed Central - PubMed

Affiliation: International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya; Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.

ABSTRACT
Rift Valley fever (RVF) outbreaks in Kenya have increased in frequency and range to include northeastern Kenya where viruses are increasingly being isolated from known (Aedes mcintoshi) and newly-associated (Ae. ochraceus) vectors. The factors contributing to these changing outbreak patterns are unclear and the population genetic structure of key vectors and/or specific virus-vector associations, in particular, are under-studied. By conducting mitochondrial and nuclear DNA analyses on >220 Kenyan specimens of Ae. mcintoshi and Ae. ochraceus, we uncovered high levels of vector complexity which may partly explain the disease outbreak pattern. Results indicate that Ae. mcintoshi consists of a species complex with one of the member species being unique to the newly-established RVF outbreak-prone northeastern region of Kenya, whereas Ae. ochraceus is a homogeneous population that appears to be undergoing expansion. Characterization of specimens from a RVF-prone site in Senegal, where Ae. ochraceus is a primary vector, revealed direct genetic links between the two Ae. ochraceus populations from both countries. Our data strongly suggest that unlike Ae. mcintoshi, Ae. ochraceus appears to be a relatively recent, single 'introduction' into Kenya. These results, together with increasing isolations from this vector, indicate that Ae. ochraceus will likely be of greater epidemiological importance in future RVF outbreaks in Kenya. Furthermore, the overall vector complexity calls into question the feasibility of mosquito population control approaches reliant on genetic modification.

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Related in: MedlinePlus

Maximum likelihood tree derived for concatenated dataset (COI+ITS) of A). Ae. mcintoshi and B) Ae. ochraceus, from Kenya and Senegal.Bootstrap values and Bayesian support values are shown above and below relevant nodes, respectively. Sequence of Ae. ochraceus indicated as outgroup for Ae. mcintoshi and vice versa. Taxon abbreviations follow those provided in Table 2 with numbers corresponding to specific sequence samples.
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pntd-0003364-g002: Maximum likelihood tree derived for concatenated dataset (COI+ITS) of A). Ae. mcintoshi and B) Ae. ochraceus, from Kenya and Senegal.Bootstrap values and Bayesian support values are shown above and below relevant nodes, respectively. Sequence of Ae. ochraceus indicated as outgroup for Ae. mcintoshi and vice versa. Taxon abbreviations follow those provided in Table 2 with numbers corresponding to specific sequence samples.

Mentions: Individual gene phylogenies for Ae. mcintoshi revealed topological incongruence which was limited to certain poorly supported nodes or clade assignments. However, the concatenated dataset (COI+ITS) recovered four distinct clades (I, II, III, IV) which were well supported by the ML analysis (bootstrap support ≥85; Fig. 2A). The pattern of four well-supported clades was also reflected in the Ae. mcintoshi COI barcode region phylogeny, long stretch of COI and the ITS dataset (Figures S3, S4 and S5). Furthermore, analysis of ITS dataset by ML showed good bootstrap support (BS = 95 and 98, respectively) for two sub-clades within clade IV but this substructure was not supported by the BI (PP = 0.53 and 0.66) (Figure S5).


Population genetics of two key mosquito vectors of Rift Valley Fever virus reveals new insights into the changing disease outbreak patterns in Kenya.

Tchouassi DP, Bastos AD, Sole CL, Diallo M, Lutomiah J, Mutisya J, Mulwa F, Borgemeister C, Sang R, Torto B - PLoS Negl Trop Dis (2014)

Maximum likelihood tree derived for concatenated dataset (COI+ITS) of A). Ae. mcintoshi and B) Ae. ochraceus, from Kenya and Senegal.Bootstrap values and Bayesian support values are shown above and below relevant nodes, respectively. Sequence of Ae. ochraceus indicated as outgroup for Ae. mcintoshi and vice versa. Taxon abbreviations follow those provided in Table 2 with numbers corresponding to specific sequence samples.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256213&req=5

pntd-0003364-g002: Maximum likelihood tree derived for concatenated dataset (COI+ITS) of A). Ae. mcintoshi and B) Ae. ochraceus, from Kenya and Senegal.Bootstrap values and Bayesian support values are shown above and below relevant nodes, respectively. Sequence of Ae. ochraceus indicated as outgroup for Ae. mcintoshi and vice versa. Taxon abbreviations follow those provided in Table 2 with numbers corresponding to specific sequence samples.
Mentions: Individual gene phylogenies for Ae. mcintoshi revealed topological incongruence which was limited to certain poorly supported nodes or clade assignments. However, the concatenated dataset (COI+ITS) recovered four distinct clades (I, II, III, IV) which were well supported by the ML analysis (bootstrap support ≥85; Fig. 2A). The pattern of four well-supported clades was also reflected in the Ae. mcintoshi COI barcode region phylogeny, long stretch of COI and the ITS dataset (Figures S3, S4 and S5). Furthermore, analysis of ITS dataset by ML showed good bootstrap support (BS = 95 and 98, respectively) for two sub-clades within clade IV but this substructure was not supported by the BI (PP = 0.53 and 0.66) (Figure S5).

Bottom Line: Our data strongly suggest that unlike Ae. mcintoshi, Ae. ochraceus appears to be a relatively recent, single 'introduction' into Kenya.These results, together with increasing isolations from this vector, indicate that Ae. ochraceus will likely be of greater epidemiological importance in future RVF outbreaks in Kenya.Furthermore, the overall vector complexity calls into question the feasibility of mosquito population control approaches reliant on genetic modification.

View Article: PubMed Central - PubMed

Affiliation: International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya; Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.

ABSTRACT
Rift Valley fever (RVF) outbreaks in Kenya have increased in frequency and range to include northeastern Kenya where viruses are increasingly being isolated from known (Aedes mcintoshi) and newly-associated (Ae. ochraceus) vectors. The factors contributing to these changing outbreak patterns are unclear and the population genetic structure of key vectors and/or specific virus-vector associations, in particular, are under-studied. By conducting mitochondrial and nuclear DNA analyses on >220 Kenyan specimens of Ae. mcintoshi and Ae. ochraceus, we uncovered high levels of vector complexity which may partly explain the disease outbreak pattern. Results indicate that Ae. mcintoshi consists of a species complex with one of the member species being unique to the newly-established RVF outbreak-prone northeastern region of Kenya, whereas Ae. ochraceus is a homogeneous population that appears to be undergoing expansion. Characterization of specimens from a RVF-prone site in Senegal, where Ae. ochraceus is a primary vector, revealed direct genetic links between the two Ae. ochraceus populations from both countries. Our data strongly suggest that unlike Ae. mcintoshi, Ae. ochraceus appears to be a relatively recent, single 'introduction' into Kenya. These results, together with increasing isolations from this vector, indicate that Ae. ochraceus will likely be of greater epidemiological importance in future RVF outbreaks in Kenya. Furthermore, the overall vector complexity calls into question the feasibility of mosquito population control approaches reliant on genetic modification.

Show MeSH
Related in: MedlinePlus