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Enhanced understanding of the transmission dynamics and population genetics for Plasmodium vivax is crucial in predicting the emergence and spread of novel parasite phenotypes with major public health implications, such as new relapsing patterns, drug resistance and increased virulence. Suitable molecular markers are required for these population genetic studies. Here, we focus on two groups of molecular markers that are commonly used to analyse natural populations of P. vivax. We use markers under selective pressure, for instance, antigen-coding polymorphic genes, and markers that are not under strong natural selection, such as most minisatellite and microsatellite loci. First, we review data obtained using genes encoding for P. vivax antigens: circumsporozoite protein, merozoite surface proteins 1 and 3α, apical membrane antigen 1 and Duffy binding antigen. We next address neutral or nearly neutral molecular markers, especially microsatellite loci, providing a complete list of markers that have already been used in P. vivax populations studies. We also analyse the microsatellite loci identified in the P. vivax genome project. Finally, we discuss some practical uses for P. vivax genotyping, for example, detecting multiple-clone infections and tracking the geographic origin of isolates.

Complete DNA sequences of the small subunit ribosomal RNA (SSUrRNA) gene and partial sequences of three other loci were obtained from three variant-type and three classic-type Plasmodium ovale isolates from Southeast Asia and compared with GenBank-available data. Three different SSUrRNA sequences (Pov 1-3) were found in each variant-type isolate, and two different SSUrRNA sequences (Poc 1-2) in each classic-type isolate. Pov 1-3 were closer to sequences previously found in the Cameroon and MAL/MAI isolates, whereas Poc 1-2 were closer to sequences previously found in two clones of the Nigerian I/CDC strain. The 3' half of Pov 1-3 was identical to the partial sequence of the SSUrRNA gene from the London School (LS) strain. Results support grouping P. ovale into two groups, the classic type (including the Nigerian I/CDC strain) and the variant type (Cameroon, MAL/MAI, and LS isolates).

Most studies of genetic variability of Plasmodium falciparum have focused on protein antigens and the genes that encode them. The consensus is that populations exhibit high levels of genetic polymorphism, most notably the genes encoding surface proteins of the merozoite (Msp1, Msp2) and the sporozoite (Csp). The age and derivation of this variation is a subject that warrants further careful consideration, as discussed here by Stephen Rich, Marcelo Ferreira and Francisco Ayala.