Environmental factors influence the local establishment of Wolbachia in Aedes aegypti mosquitoes in two small communities in central Vietnam
Nguyễn Trần Hiển, Đặng Đức Anh, Nguyen Hoang Le, Nguyen T. Yen, Trần Vũ Phong, Vũ Sinh Nam, Trần Như Dương, Nguyen B. Nguyen, Duong T.T. Huong, Luu Q. Hung, Chau N.T. Trinh, Nguyễn Viết Hoàng, Vien Q. Mai, Lê Trung Nghĩa, Nguyễn Thành Đông, Le Huu Tho, Simon C. Kutcher, Tim Hurst, Jacqui Montgomery, Megan Woolfit, Edwige Rancès, Le Nguyen, Jack Brown-Kenyon, Angela Caird, Breeanna J. McLean, Iñaki Iturbe‐Ormaetxe, Scott A. Ritchie, Scott L. O’Neill, Peter A. Ryan
Abstract
<ns4:p> <ns4:bold>Background:</ns4:bold> The <ns4:italic>w</ns4:italic> Mel strain of <ns4:italic>Wolbachia</ns4:italic> has been successfully introduced into <ns4:italic>Aedes aegypti</ns4:italic> mosquitoes and subsequently shown to reduce transmission of dengue and other pathogens, under both laboratory and field conditions. Here we describe the entomological outcomes of <ns4:italic>w</ns4:italic> Mel <ns4:italic>Wolbachia</ns4:italic> mosquito releases in two small communities in Nha Trang City in central Vietnam. </ns4:p> <ns4:p> <ns4:bold>Methods:</ns4:bold> The <ns4:italic>w</ns4:italic> Mel strain of <ns4:italic>Wolbachia</ns4:italic> was backcrossed into local <ns4:italic>Aedes aegypti</ns4:italic> genotype and mosquito releases were undertaken by community members or by staff. Field monitoring was undertaken to track <ns4:italic>Wolbachia</ns4:italic> establishment in local <ns4:italic>Ae. aegypti</ns4:italic> mosquito populations. Ecological studies were undertaken to assess relationships between environmental factors and the spatial and temporal variability in <ns4:italic>Wolbachia</ns4:italic> infection prevalence in mosquitoes. </ns4:p> <ns4:p> <ns4:bold>Results:</ns4:bold> Releases of <ns4:italic>w</ns4:italic> Mel <ns4:italic>Wolbachia Ae. aegypti</ns4:italic> mosquitoes in two small communities in Nha Trang City resulted in the initial establishment of <ns4:italic>Wolbachia</ns4:italic> in the local <ns4:italic>Ae. aegypti</ns4:italic> mosquito populations, followed by seasonal fluctuations in <ns4:italic>Wolbachia</ns4:italic> prevalence. There was significant small-scale spatial heterogeneity in <ns4:italic>Wolbachia</ns4:italic> infection prevalence in the Tri Nguyen Village site, resulting in the loss of <ns4:italic>w</ns4:italic> Mel <ns4:italic>Wolbachia</ns4:italic> infection in mosquitoes in north and center areas, despite <ns4:italic>Wolbachia</ns4:italic> prevalence remaining high in mosquitoes in the south area. In the second site, Vinh Luong Ward, <ns4:italic>Wolbachia</ns4:italic> has persisted at a high level in mosquitoes throughout this site despite similar seasonal fluctuations in <ns4:italic>w</ns4:italic> Mel <ns4:italic>Wolbachia</ns4:italic> prevalence. </ns4:p> <ns4:p> <ns4:bold>Conclusion:</ns4:bold> Seasonal variation in <ns4:italic>Wolbachia</ns4:italic> infection prevalence in mosquitoes was associated with elevated temperature conditions, and was possibly due to imperfect maternal transmission of <ns4:italic>Wolbachia</ns4:italic> . Heterogeneity in <ns4:italic>Wolbachia</ns4:italic> infection prevalence was found throughout one site, and indicates additional factors may influence <ns4:italic>Wolbachia</ns4:italic> establishment. </ns4:p>