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

In Mexico, Plasmodium vivax 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 pvs25 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 pvcsp were detected, and VK210 had greater haplotype diversity (0.860) than VK247 parasites (0.198). Two pvs25 mutations (Q87K and I130T) yielded three haplotypes, and two ribosomal variants were detected. Gene and multilocus haplotype frequencies varied among malarious foci (p < 0.001). An AMOVA test, F_ST values, and Spearman's correlation suggested a structured P. vivax population among the malaria foci. Each malaria focus across the northwestern and southern regions retained a portion of the past countrywide P. vivax population, which seems unique in Latin America. In the Lacandon region (LR), a linkage equilibrium between pvs25 haplotypes and the ribosomal variants within the VK247 or VK210 populations was observed. This region harbored the broadest reservoir of P. vivax 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.