Abstract
Levels of genetic diversity of the malaria parasites and multiclonal infections are correlated with transmission intensity. In order to monitor the effect of strengthened malaria control efforts in recent years at the China–Myanmar border area, we followed the temporal dynamics of genetic diversity of three polymorphic antigenic markers msp1, msp2, and glurp in the Plasmodium falciparum populations. Despite reduced malaria prevalence in the region, parasite populations exhibited high levels of genetic diversity. Genotyping 258 clinical samples collected in four years detected a total of 22 PCR size alleles. Multiclonal infections were detected in 45.7% of the patient samples, giving a minimum multiplicity of infection of 1.41. The majority of alleles experienced significant temporal fluctuations through the years. Haplotype diversity based on the three-locus genotypes ranged from the lowest in 2009 at 0.33 to the highest in 2010 at 0.80. Sequencing of msp1 fragments from 36 random samples of five allele size groups detected 13 different sequences, revealing an additional layer of genetic complexity. This study suggests that despite reduced prevalence of malaria infections in this region, the parasite population size and transmission intensity remained high enough to allow effective genetic recombination of the parasites and continued maintenance of genetic diversity.
Highlights
Malaria continues to be a major public health problem in the developing world
The extensive polymorphisms in these vaccine candidates are a major impediment for subunit vaccines against the malaria parasites
For msp1, MAD20 was more common than K1 and RO33, similar to other parts of the Greater Mekong Subregion (GMS) such as Yunnan Province, China (Zhu et al, 1999), Laos (Khaminsou et al, 2011), and Thailand (Snounou et al, 1999)
Summary
Malaria continues to be a major public health problem in the developing world. Globally, there are estimated 225 million malaria infections each year, resulting in around a million deaths (WHO, 2011). Within the SE Asian region, the Greater Mekong Subregion (GMS) has been one of the most serious foci of malaria, with immense geographical heterogeneity in disease endemicity, complex vector systems, and the co-existence of Plasmodium falciparum and Plasmodium vivax (Cui et al, 2012a). The GMS is a hotspot of multidrug resistant P. falciparum, and recent detection of artemisinin resistance in this area has raised considerable global concern (Dondorp et al, 2009; Noedl et al, 2008). Another notable feature of malaria epidemiology in the GMS is “border malaria”, with most of the malaria cases concentrated along international borders. Knowledge of accurate malaria epidemiology at both macro and micro scales is needed for targeted malaria control, especially during the elimination phase
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