title: Microgeography and molecular epidemiology of malaria at the Thailand-Myanmar border in the malaria pre-elimination phase.
abstract: BACKGROUND
  Endemic malaria in Thailand continues to only exist along international borders. This pattern is frequently attributed to importation of malaria from surrounding nations. A microgeographical approach was used to investigate malaria cases in a study village along the Thailand-Myanmar border.
  
  
  METHODS
  Three mass blood surveys were conducted during the study period (July and December 2011, and May 2012) and were matched to a cohort-based demographic surveillance system. Blood slides and filter papers were taken from each participant. Slides were cross-verified by an expert microscopist and filter papers were analysed using nested PCR. Cases were then mapped to households and analysed using spatial statistics. A risk factor analysis was done using mixed effects logistic regression.
  
  
  RESULTS
  In total, 55 Plasmodium vivax and 20 Plasmodium falciparum cases (out of 547 participants) were detected through PCR, compared to six and two (respectively) cases detected by field microscopy. The single largest risk factor for infection was citizenship. Many study participants were ethnic Karen people with no citizenship in either Thailand or Myanmar. This subpopulation had over eight times the odds of malaria infection when compared to Thai citizens. Cases also appeared to cluster near a major drainage system and year-round water source within the study village.
  
  
  CONCLUSIONS
  This research indicates that many cases of malaria remain undiagnosed in the region. The spatial and demographic clustering of cases in a sub-group of the population indicates either transmission within the Thai village or shared exposure to malaria vectors outside of the village. While it is possible that malaria is imported to Thailand from Myanmar, the existence of undetected infections, coupled with an ecological setting that is conducive to malaria transmission, means that indigenous transmission could also occur on the Thai side of the border. Improved, timely, and active case detection is warranted.
authors.affiliation: Department of Anthropology, The Pennsylvania State University, 409 Carpenter Building, University Park, PA, USA. daniel@shoklo-unit.com.|Population Research Institute, The Pennsylvania State University, 601 Oswald Tower, University Park, PA, USA. daniel@shoklo-unit.com.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Parker
authors.affiliation: Department of Anthropology, The Pennsylvania State University, 409 Carpenter Building, University Park, PA, USA. sxm27@psu.edu.|Population Research Institute, The Pennsylvania State University, 601 Oswald Tower, University Park, PA, USA. sxm27@psu.edu.|Department of Sociology, The Pennsylvania State University, 601 Oswald Tower, University Park, PA, USA. sxm27@psu.edu.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Matthews
authors.affiliation: Program in Public Health, University of California at Irvine, Irvine, CA, USA. guiyuny@uci.edu.
authors.forename: Guiyun
authors.initials: G
authors.lastname: Yan
authors.affiliation: Program in Public Health, University of California at Irvine, Irvine, CA, USA. zhoug@uci.edu.
authors.forename: Guofa
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Program in Public Health, University of California at Irvine, Irvine, CA, USA. mingchil@uci.edu.
authors.forename: Ming-Chieh
authors.initials: MC
authors.lastname: Lee
authors.affiliation: Bureau of Vector Borne Diseases, Pra Phuttabhat, Thailand. grphat@hotmail.com.
authors.forename: Jeeraphat
authors.initials: J
authors.lastname: Sirichaisinthop
authors.affiliation: Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. kirakorn06@gmail.com.
authors.forename: Kirakorn
authors.initials: K
authors.lastname: Kiattibutr
authors.affiliation: Dalian Institute of Biotechnology, Dalian, Liaoning Province, China. fanqi2002@yahoo.com.
authors.forename: Qi
authors.initials: Q
authors.lastname: Fan
authors.affiliation: Dalian Institute of Biotechnology, Dalian, Liaoning Province, China. ppttkx@163.com.
authors.forename: Peipei
authors.initials: P
authors.lastname: Li
authors.affiliation: Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. jetsumon.pra@mahidol.ac.th.
authors.forename: Jetsumon
authors.initials: J
authors.lastname: Sattabongkot
authors.affiliation: Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, PA, USA. luc2@psu.edu.
authors.forename: Liwang
authors.initials: L
authors.lastname: Cui
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000469:parasitology; D016780:Malaria, Vivax / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000235:genetics / Q000502:physiology*; D010966:Plasmodium vivax / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000235:genetics; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology; D055815:Young Adult
chemical_list: D015800:Protozoan Proteins