Plasmodium simium: Population Genomics Reveals the Origin of a Reverse Zoonosis.

BACKGROUND: The population history of Plasmodium simium, which causes malaria in sylvatic Neotropical monkeys and humans along the Atlantic Coast of Brazil, remains disputed. Genetically diverse P vivax populations from various sources, including the lineages that founded the species P simium, are thought to have arrived in the Americas in separate migratory waves. METHODS: We use population genomic approaches to investigate the origin and evolution of P simium. RESULTS: We find a minimal genome-level differentiation between P simium and present-day New World P vivax isolates, consistent with their common geographic origin and subsequent divergence on this continent. The meagre genetic diversity in P simium samples from humans and monkeys implies a recent transfer from humans to non-human primates - a unique example of malaria as a reverse zoonosis of public health significance. Likely genomic signatures of P simium adaptation to new hosts include the deletion of >40% of a key erythrocyte invasion ligand, PvRBP2a, which may have favored more efficient simian host cell infection. CONCLUSIONS: New World P vivax lineages that switched from humans to platyrrhine monkeys founded the P simium population that infects nonhuman primates and feeds sustained human malaria transmission in the outskirts of major cities.

Human migration and the spread of malaria parasites to the New World.

We examined the mitogenomes of a large global collection of human malaria parasites to explore how and when Plasmodium falciparum and P. vivax entered the Americas. We found evidence of a significant contribution of African and South Asian lineages to present-day New World malaria parasites with additional P. vivax lineages appearing to originate from Melanesia that were putatively carried by the Australasian peoples who contributed genes to Native Americans. Importantly, mitochondrial lineages of the P. vivax-like species P. simium are shared by platyrrhine monkeys and humans in the Atlantic Forest ecosystem, but not across the Amazon, which most likely resulted from one or a few recent human-to-monkey transfers. While enslaved Africans were likely the main carriers of P. falciparum mitochondrial lineages into the Americas after the conquest, additional parasites carried by Australasian peoples in pre-Columbian times may have contributed to the extensive diversity of extant local populations of P. vivax.