Population Dynamics of Plasmodium vivax in Mexico Determined by CSP, Pvs25, and SSU 18S rRNA S-Type Polymorphism Analyses

In Mexico, <i>Plasmodium vivax</i> transmission has been confined to the northwestern and southern regions since 2000. Parasites from five malaria foci were analyzed using three genetic markers. The circumsporozoite gene was examined by PCR-RFLP and sequencing, and <i>pvs25</i> mutations and variants of ribosomal 18S SSU rRNA S-type were also determined. Previous data from the southernmost Pacific in Chiapas were included in the analysis. Both the VK210 and VK247 types of <i>pvcsp</i> were detected, and VK210 had greater haplotype diversity (0.860) than VK247 parasites (0.198). Two <i>pvs25</i> mutations (Q87K and I130T) yielded three haplotypes, and two ribosomal variants were detected. Gene and multilocus haplotype frequencies varied among malarious foci (<i>p</i> < 0.001). An AMOVA test, <i>F_ST</i> values, and Spearman's correlation suggested a structured <i>P. vivax</i> population among the malaria foci. Each malaria focus across the northwestern and southern regions retained a portion of the past countrywide <i>P. vivax</i> population, which seems unique in Latin America. In the Lacandon region (LR), a linkage equilibrium between <i>pvs25</i> haplotypes and the ribosomal variants within the VK247 or VK210 populations was observed. This region harbored the broadest reservoir of <i>P. vivax</i> haplotypes, and the high adaptation of parasites in the northwestern region represents a challenge for malaria elimination. These finding are relevant for monitoring and epidemiological surveillance.