title: Genetic diversity and population structure of Plasmodium vivax in Central China.
abstract: BACKGROUND
  In Central China the declining incidence of Plasmodium vivax has been interrupted by epidemic expansions and imported cases. The impact of these changes on the local parasite population, and concurrent risks of future resurgence, was assessed.
  
  
  METHODS
  Plasmodium vivax isolates collected from Anhui and Jiangsu provinces, Central China between 2007 and 2010 were genotyped using capillary electrophoresis at seven polymorphic short tandem repeat markers. Spatial and temporal analyses of within-host and population diversity, population structure, and relatedness were conducted on these isolates.
  
  
  RESULTS
  Polyclonal infections were infrequent in the 94 isolates from Anhui (4%) and 25 from Jiangsu (12%), with a trend for increasing frequency from 2008 to 2010 (2 to 19%) when combined. Population diversity was high in both provinces and across the years tested (H(E) = 0.8 - 0.85). Differentiation between Anhui and Jiangsu was modest (F'(ST) = 0.1). Several clusters of isolates with identical multi-locus haplotypes were observed across both Anhui and Jiangsu. Linkage disequilibrium was strong in both populations and in each year tested (I(A)(S) = 0.2 - 0.4), but declined two- to four-fold when identical haplotypes were accounted for, indicative of occasional epidemic transmission dynamics. None of five imported isolates shared identical haplotypes to any of the central Chinese isolates.
  
  
  CONCLUSIONS
  The population genetic structure of P. vivax in Central China highlights unstable transmission, with limited barriers to gene flow between the central provinces. Despite low endemicity, population diversity remained high, but the reservoirs sustaining this diversity remain unclear. The challenge of imported cases and risks of resurgence emphasize the need for continued surveillance to detect early warning signals. Although parasite genotyping has potential to inform the management of outbreaks, further studies are required to identify suitable marker panels for resolving local from imported P. vivax isolates.
authors.forename: Yaobao
authors.initials: Y
authors.lastname: Liu
authors.forename: Sarah
authors.initials: S
authors.lastname: Auburn
authors.forename: Jun
authors.initials: J
authors.lastname: Cao
authors.forename: Hidayat
authors.initials: H
authors.lastname: Trimarsanto
authors.forename: Huayun
authors.initials: H
authors.lastname: Zhou
authors.forename: Karen-Ann
authors.initials: KA
authors.lastname: Gray
authors.forename: Taane G
authors.initials: TG
authors.lastname: Clark
authors.forename: Ric N
authors.initials: RN
authors.lastname: Price
authors.forename: Qin
authors.initials: Q
authors.lastname: Cheng
authors.affiliation: Medical College of Soochow University, Suzhou, Jiangsu, People's Republic of China. hruisdm@163.com.
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.forename: Qi
authors.initials: Q
authors.lastname: Gao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D014644:Genetic Variation; D006801:Humans; D016780:Malaria, Vivax / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D008297:Male; D008875:Middle Aged; D018598:Minisatellite Repeats; D017720:Molecular Epidemiology; D010966:Plasmodium vivax / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D055815:Young Adult