Differences in genetic population structures of Plasmodium falciparum isolates from patients along Thai-Myanmar border with severe or uncomplicated malaria

Twelve microsatellite DNA loci from P. falciparum were used to assess the population genetic structures of 50 isolates (i.e., 25 isolates from patients with severe malaria and 25 from patients with uncomplicated malaria) collected in the Thai-Myanmar border area between 2002 and 2005.Genetic diversity and effective population sizes were greater in the uncomplicated malaria group than in the severe malaria group. Evidence of genetic bottlenecks was not observed in either group. Strong linkage disequilibrium was observed in the uncomplicated malaria group. The groups demonstrated significant genetic differentiation (P < 0.05), and allele frequencies for 3 of the 12 microsatellite loci differed significantly between the two groups.These findings suggest that the genetic structure of P. falciparum populations in patients with severe malaria differs from that in patients with uncomplicated malaria. The microsatellite loci used in this study were presumably unrelated to antigenic features of the parasites, but, these findings suggest that some loci may influence the clinical outcome of malaria.Plasmodium falciparum is the most pathogenic of the protozoan parasites that cause human malaria. According to the World Health Organization, more than 1 million people die from malaria each year [1]. The clinical manifestations of malaria are quite pleomorphic, ranging from mild or asymptomatic parasitemia to potentially fatal conditions such as coma and multi-organ failure. Although the molecular basis of severe malaria has been well studied in recent years [2], determinants of the clinical outcomes of malaria remain unknown. Several factors, including host and parasite genetic characteristics, are thought to contribute to the clinical outcome of malaria.Several studies have reported evidence of a relationship between parasite genotype and clinical outcome [2-8]. Ariey et al found that certain alleles in the polymorphic microsatellite loci of clinical isolates from French Guyana w