Diversity and evolutionary genetics of the three major Plasmodium vivax merozoite genes participating in reticulocyte invasion in southern Mexico

BACKGROUND: Reported malaria cases in the Americas had been reduced to about one-half million by 2012. To advance towards elimination of this disease, it is necessary to gain insights into how the malaria parasite is evolving, including the emergence, spread and persistence of new haplotypes in affected regions. In here, the genetic diversity of the three major P. vivax merozoite genes was analyzed. METHODS: From P. vivax-infected blood samples obtained in southern Mexico (SMX) during 2006–2007, nucleotide sequences were achieved for: the 42 kDa carboxyl fragment of the merozoite surface protein-1 (msp1(42)), domains I-II of the apical membrane antigen-1 (ama1(I-II)), and domain II of the Duffy binding protein (dbp(II)). Gene polymorphism was examined and haplotype networks were developed to depict parasite relationships in SMX. Then genetic diversity, recombination and natural selection were analyzed and the degree of differentiation was determined as F(ST) values. RESULTS: The diversity of P. vivax merozoite genes in SMX was less than that of parasites from other geographic origins, with dbp(II) < ama1(I-II) < msp1(42). Ama1(I-II) and msp1(42) exposed the more numerous haplotypes exclusive to SMX. While, all dbp(II) haplotypes from SMX were separated from one to three mutational steps, the networks of ama1(I-II) and msp1(42) were more complex; loops and numerous mutational steps were evidenced, likely due to recombination. Sings of local diversification were more evident for msp1(42). Sixteen combined haplotypes were determined; one of these haplotypes not detected in 2006 was highly frequent in 2007. The Rm value was higher for msp1(42)than for ama1(I-II,) being insignificant for dbp(II). The dN-dS value was highly significant for ama1(I-II) and lesser so for dbp(II). The F(ST) values were higher for dbp(II) than msp1(42), and very low for ama1(I-II). CONCLUSIONS: In SMX, P. vivax ama1(I-II), dbp(II) and msp1(42) demonstrated limited diversity, and exhibited a differentiated parasite population. The results suggest that differential intensities of selective forces are operating on these gene fragments, and probably related to their timing, length of exposure and function during reticulocyte adhesion and invasion. Therefore, these finding are essential for mono and multivalent vaccine development and for epidemiological surveillance. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-015-1266-7) contains supplementary material, which is available to authorized users.