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Open Access Research

Genetic diversity and population structure of Plasmodium vivax in Central China

Yaobao Liu12, Sarah Auburn3, Jun Cao2, Hidayat Trimarsanto4, Huayun Zhou2, Karen-Ann Gray5, Taane G Clark6, Ric N Price37, Qin Cheng5, Rui Huang1* and Qi Gao2*

Author Affiliations

1 Medical College of Soochow University, Suzhou, Jiangsu, People’s Republic of China

2 Jiangsu Institute of Parasitic Diseases, Key Laboratory of Parasitic Disease Control and Prevention (Ministry of Health), Jiangsu Provincial Key Laboratory of Parasite Molecular Biology, Wuxi, Jiangsu, People’s Republic of China

3 Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Northern Territory, Australia

4 Eijkman Institute for Molecular Biology, Jakarta, Indonesia

5 Drug Resistance and Diagnostics, Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, Queensland, Australia

6 Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK

7 Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK

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Malaria Journal 2014, 13:262  doi:10.1186/1475-2875-13-262

Published: 9 July 2014

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 (HE = 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 (IAS = 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.

Keywords:
Plasmodium vivax; China; Anhui; Jiangsu; Population genetics; Population structure; Transmission; Diversity