Origin of the New World Plasmodium vivax: Facts and New Approaches

Malaria is one of the most important human diseases throughout tropical and sub-tropical regions of the world. Global distribution and ample host range have contributed to the genetic diversity of the etiological agent, Plasmodium. Phylogeographical analyses demonstrated that Plasmodium falciparum and Plasmodium vivax follow an Out of Africa (OOA) expansion, having a higher genetic diversity in African populations and a low genetic diversity in South American populations. Modeling the evolutionary rate of conserved genes for both P. falciparum and P. vivax determined the approximate arrival of human malaria in South America. Bayesian computational methods suggest that P. falciparum originated in Africa and arrived in South America through multiple independent introductions by the transatlantic African slave trade; however, in South America, P. vivax could have been introduced through an alternate migratory route. Alignments of P. vivax mitogenomes have revealed low genetic variation between the South American and Southeast Asian populations suggesting introduction through either pre-Columbian human migration or post-colonization events. To confirm the findings of these phylogeographical analyses, molecular methods were used to diagnose malaria infection in archeological remains of pre-Columbian ethnic groups. Immunohistochemistry tests were used and identified P. vivax but not P. falciparum in histologically prepared tissues from pre-Columbian Peruvian mummies, whereas shotgun metagenomics sequencing of DNA isolated from pre-Columbian Caribbean coprolites revealed Plasmodium-homologous reads; current evidence suggests that only P. vivax might have been present in pre-Columbian South America.