Population dynamics of genetically diversePlasmodium falciparumlineages: community-based prospective study in rural Amazonia

Abstract

SUMMARY: Temporal changes in the prevalence of antigenic variants inPlasmodium falciparumpopulations have been interpreted as evidence of immune-mediated frequency-dependent selection, but evolutively neutral processes may generate similar patterns of serotype replacement. Over 4 years, we investigated the population dynamics ofP. falciparumpolymorphisms at the community level by using 11 putatively neutral microsatellite markers.Plasmodium falciparumpopulations were less diverse than sympatricP. vivaxisolates, with less multiple-clone infections, lower number of alleles per locus and lower virtual heterozygosity, but both species showed significant multilocus linkage disequilibrium. Evolutively neutralP. falciparumpolymorphisms showed a high turnover rate, with few lineages persisting for several months in the population. Similar results had previously been obtained, in the same community, for sympatricP. vivaxisolates. In contrast, the prevalence of the 2 dimorphic types of a major antigen, MSP-2, remained remarkably stable throughout the study period. We suggest that the relatively fast turnover of parasite lineages represents the typical population dynamics of neutral polymorphisms in small populations, with clear implications for the detection of frequency-dependent selection of polymorphisms.