Higher microsatellite diversity in Plasmodium vivax than in sympatric Plasmodium falciparum populations in Pursat, Western Cambodia

Abstract

Previous microsatellite analyses of sympatric populations of Plasmodium vivax and P. falciparum in Brazil revealed higher diversity in the former species. However, it remains unclear whether regional species-specific differences in prevalence and transmission levels might account for these findings. Here, we examine sympatric populations of P. vivax (n = 87) and P. falciparum (n = 164) parasites from Pursat province, western Cambodia, where both species are similarly prevalent. Using 10 genome-wide microsatellites for P. falciparum and 13 for P. vivax, we found that the P. vivax population was more diverse than the sympatric P. falciparum population (average virtual heterozygosity [HE], 0.87 vs. 0.66, P = 0.003), with more multiple-clone infections (89.6% vs. 47.6%) and larger mean number of alleles per marker (16.2 vs. 11.1, P = 0.07). Both populations showed significant multi-locus linkage disequilibrium suggestive of a predominantly clonal mode of parasite reproduction. The higher microsatellite diversity found in P. vivax isolates, compared to sympatric P. falciparum isolates, does not necessarily result from local differences in transmission level and may reflect differences in population history between species or increased mutation rates in P. vivax.

Selective sweep suggests transcriptional regulation may underlie Plasmodium vivax resilience to malaria control measures in Cambodia

“…These peculiarities of the malaria lifecycle may skew the allele-frequency spectrum toward increased singletons, even at neutral sites, leading to quantitatively or even qualitatively inappropriate demographic conclusions (79). However, our demographic conclusions are supported by epidemiologic observation as well as by the results of other population genetic studies (6,13). Because extensive recognized and unrecognized paralogous families in the P. vivax genome present significant mapping and variant-calling challenges, we curated our data carefully, performing extensive tests to determine the best alignment, filtering, and variant-calling approaches.…”

“…Studies of microsatellites and highly variable antigens of sympatric P. vivax and P. falciparum populations in Southeast Asia and the Southwest Pacific have consistently shown P. vivax populations to be more diverse, with a higher effective population size (N eff ), more stable transmission, and increased gene flow between geographic islands, whereas P. falciparum populations tend to be clonal with episodic transmission and structure-by-geography (10)(11)(12)(13)(14)(15). We hypothesized that the species have evolved disparate responses to selective pressures and that genomic studies of sympatric Plasmodium sp.…”

Uncovering the transmission dynamics ofPlasmodium vivaxusing population genetics

“…transmission dynamics) and in order to provide findings useful to control and elimination programmes, it will be important to define parasite population structure by quantifying genetic relationships among the different parasite clones and populations. 8,9 The recognition that P. vivax has distinct patterns of population genetic structure compared to P. falciparum globally 10 and in areas of similar endemicity 11,12 is consistent with higher rates of genetic exchange between P. vivax parasites and populations. A major driver of the patterns observed may therefore be the hypnozoite and its capacity to cause relapsing infections several weeks and even months after the primary infection, resulting in a large proportion of infections containing multiple clones.…”

“…Recent studies comparing the population genetics of P. vivax with P. falciparum suggest that its unique biological characteristics enhance its transmission potential 11,12 (Table 1) and may explain why this parasite can persist in co-endemic areas despite the near elimination of P. falciparum. 2,14 P. vivax is more genetically diverse and has less structured populations compared to P. falciparum.…”

“…2,14 P. vivax is more genetically diverse and has less structured populations compared to P. falciparum. [10][11][12] At high transmission, new infections in addition to relapse would increase the rate of recombination between distinct clones and a breakdown in LD compared to that of P. falciparum, which does not relapse. 11 Furthermore, the carriage of clones as dormant hypnozoites in mobile human populations would increase rates of gene flow thus limiting population structure.…”