Comparison of microsatellite and antigen-coding loci for differentiating recrudescing Plasmodium falciparum infections from reinfections in Kenya.

We have compared the ability of five Plasmodium falciparum microsatellites and three antigen-coding loci to differentiate recrudescence from reinfection. We used 133 pairs of P. falciparum-infected blood samples collected during in vivo drug efficacy trials from three sites in Kenya with different malaria endemicities. There were no significant differences between the marker subsets in their ability to discriminate recrudescences from new infections across the three sites. Overall, microsatellite loci revealed significantly higher expected heterozygosity and multiplicity of infection levels than antigen-coding loci. The mean expected heterozygosity across all loci in the three populations was significantly higher with microsatellites (0.70, 0.78 and 0.79) than antigen-coding loci (0.53, 0.60 and 0.62) for Mwea, Tiwi and Bondo areas, respectively. These observations can be explained by three non-exclusive hypotheses: (i) microsatellites are more polymorphic than antigenic loci; (ii) partially immune hosts remove certain parasites from infections on the basis of their antigenic alleles; and/or (iii) recombination occurs in vitro or in vivo with microsatellites.