Global and local genetic diversity at two microsatellite loci in Plasmodium vivax parasites from Asia, Africa and South America

Background: Even though Plasmodium vivax has the widest worldwide distribution of the human malaria species
and imposes a serious impact on global public health, the investigation of genetic diversity in this species has been
limited in comparison to Plasmodium falciparum. Markers of genetic diversity are vital to the evaluation of drug and
vaccine efficacy, tracking of P. vivax outbreaks, and assessing geographical differentiation between parasite
populations.
Methods: The genetic diversity of eight P. vivax populations (n = 543) was investigated by using two microsatellites
(MS), m1501 and m3502, chosen because of their seven and eight base-pair (bp) repeat lengths, respectively. These
were compared with published data of the same loci from six other P. vivax populations.
Results: In total, 1,440 P. vivax samples from 14 countries on three continents were compared. There was highest
heterozygosity within Asian populations, where expected heterozygosity (He) was 0.92-0.98, and alleles with a high
repeat number were more common. Pairwise FST revealed significant differentiation between most P. vivax
populations, with the highest divergence found between Asian and South American populations, yet the majority
of the diversity (~89%) was found to exist within rather than between populations.
Conclusions: The MS markers used were informative in both global and local P. vivax population comparisons and
their seven and eight bp repeat length facilitated population comparison using data from independent studies. A
complex spatial pattern of MS polymorphisms among global P. vivax populations was observed which has potential
utility in future epidemiological studies of the P. vivax parasite.