Population Genetic Structure of Aedes (Stegomyia) aegypti (L.) at a Micro-Spatial Scale in Thailand: Implications for a Dengue Suppression Strategy Phanthip Olanratmanee 1,2 , Pattamaporn Kittayapong 1,2 *, Chitti Chansang 3 , Ary A. Hoffmann 4 , Andrew R. Weeks 4 , Nancy M. Endersby 4 1 Centre of Excellence for Vectors and Vector-Borne Diseases, Faculty of Science, Mahidol University at Salaya, Nakhon Pathom, Thailand, 2 Department of Biology, Faculty of Science, Mahidol University, Bangkok, Thailand, 3 National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand, 4 Pest and Disease Vector Control Group, Bio 21 Institute, Department of Genetics, University of Melbourne, Victoria, Australia Abstract Background: The genetic population structure of Aedes (Stegomyia) aegypti (L.), the main vector of dengue virus, is being investigated in areas where a novel dengue suppression program is to be implemented. The aim of the program is to release and establish mosquito populations with impaired virus transmission capabilities. To model effects of the release and devise protocols for its implementation, information about the genetic structure of populations at a range of spatial scales is required. Methodology/Principal Findings: This study investigates a potential release site in the Hua Sam Rong Subdistrict of Plaeng Yao District, Chachoengsao Province, in eastern Thailand which comprises a complex of five villages within a 10 km radius. Aedes aegypti resting indoors was sampled at four different times of year from houses within the five villages. Genetic markers were used to screen the mosquitoes: two Exon Primed Intron Crossing (EPIC) markers and five microsatellite markers. The raw allele size was determined using several statistical software packages to analyze the population structure of the mosquito. Estimates of effective population size for each village were low, but there was no evidence of genetic isolation by geographic distance. Conclusions: The presence of temporary genetic structure is possibly caused by genetic drift due to large contributions of adults from a few breeding containers. This suggests that the introduction of mosquitoes into an area needs to proceed through multiple releases and targeting of sites where mosquitoes are emerging in large numbers. Citation: Olanratmanee P, Kittayapong P, Chansang C, Hoffmann AA, Weeks AR, et al. (2013) Population Genetic Structure of Aedes (Stegomyia) aegypti (L.) at a Micro-Spatial Scale in Thailand: Implications for a Dengue Suppression Strategy. PLoS Negl Trop Dis 7(1): e1913. doi:10.1371/journal.pntd.0001913 Editor: Kenji Hirayama, Institute of Tropical Medicine (NEKKEN), Japan Received May 1, 2012; Accepted October 4, 2012; Published January 10, 2013 Copyright: ß 2013 Olanratmanee et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The study was funded by Bill and Melinda Gates Foundation through the Foundation for the National Institutes of Health (Grand Challenge in Global Health Program) and the Mahidol University Targeted Research Program Grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: pkittayapong@msn.com Introduction Though Aedes (Stegomyia) aegypti (L.) may have been present in Thailand in the 19 th century, its spread from major urban centers and commercial transport routes to rural villages is thought to have occurred in the last 50 years [1]. Patterns of day to day movement and distances travelled by Ae. aegypti at different spatial scales and at different densities of human settlement determine the nature of spread of dengue virus and are also important in modeling the effects of potential control strategies. Artificial infection of Ae. aegypti with strains of the bacterium, Wolbachia pipientis, has been shown to reduce vector competence of the mosquito for dengue virus [2]. Field releases of Wolbachia- infected Ae. aegypti in northern Queensland, Australia have demonstrated the feasibility of spreading a Wolbachia infection through the wild population in a localised area [3]. Future studies, in countries such as Thailand where dengue is endemic, will look at the effect of Wolbachia on dengue suppression and, if successful, will be adopted as an area-wide dengue control strategy. Detailed knowledge of population genetic structure can be translated into practical information for designing the logistics of a field release of Wolbachia-infected mosquitoes (i.e. how many mosquitoes to release, over what sized area and at what time of year). It is already known that collections of Ae. aegypti taken from four widely spaced samples in Chiang Mai Province in Thailand were highly differentiated (F ST = +0.185, P,10 24 ) when five microsatellite markers were employed [4]. Genetic structure at distances of less than 25 km and also between samples taken more than 100 km apart has also been found in Thailand using variation in a region of the NADH dehydrogenase subunit 4 mitochondrial DNA gene (ND4) [1]. Another study using 13 microsatellite loci to look at population genetics of Ae. aegypti in mainland Southeast Asian countries revealed genetic structure at all spatial scales including those at a distance of less than 500 m PLOS Neglected Tropical Diseases | www.plosntds.org 1 January 2013 | Volume 7 | Issue 1 | e1913