Last Updated: 27/01/2021

Population genomics in the main malaria hotspot of Brazil

Objectives

The study objective was to examine the patterns of genomic variation in a focus of residual malaria in the Brazilian urban Amazon.

Specifically, the study will

  • Describe new Brazilian genomes of P. vivax and compare them to pre-existing samples from two other cities in the state of Acre (Brazil), in order to verify the existence.
  • Assess the levels of genetic relatedness between different samples of parasites from Mâncio Lima and infer the introduction of new strains and their gradual. recombination with pre-existing strains in the local population of parasites.
Principal Investigators / Focal Persons

Thais Crippa de Oliveira

Rationale and Abstract

Plasmodium vivax is a neglected human malaria parasite that causes significant morbidity in the Americas, the Middle East, Asia, and the Western Pacific. Population genomic approaches remain little explored to map local and regional transmission pathways of P. vivax across the main endemic sites in the Americas, where great progress has been made towards malaria elimination over the past decades. We analyze 38 patient-derived P. vivax genome sequences from Mâncio Lima (ML) – the major Amazonian malaria hotspot next to the Brazil-Peru border – and 24 sequences from two other sites in Acre State, Brazil, a country that contributes 23% of malaria cases in the Americas. We show that P. vivax population of ML is genetically diverse (π = 4.7 ´ 10−4), with high polymorphism particularly in genes encoding proteins putatively involved in red blood cell invasion. Paradoxically, however, parasites display strong genome-wide linkage disequilibrium, being fragmented into discrete lineages that are remarkably stable across time and space, with only occasional recombination between them. Using identity-by-descent approaches, we identified a large cluster of closely related sequences that comprises 16 of 38 genomes sampled in ML over 26 months. Importantly, we found significant ancestry sharing between parasites at a large geographic distance, consistent with significant gene flow between regional P. vivax populations. We have characterized the sustained expansion of highly inbred P. vivax lineages in a malaria hotspot that can seed regional transmission. Potential source populations in such hotspots represent a priority target for malaria elimination in the Amazon. 

Study Design

Method

We analyze 38 patient-derived P. vivax genome sequences from Mâncio Lima (ML)–the Amazonian malaria hotspot next to the Brazil-Peru border—and 24 sequences from two other sites in Acre State, Brazil, a country that contributes 23% of malaria cases in the Americas. We used population genomics techniques such as nucleotide diversity, FST, linkage desequilibrium and Identity by descent to characterize gene flow between different regions in the same state and if the population is substructure.

Outcome

We characterize a genetically diverse population that displays significant linkage disequilibrium, consistent with the local circulation of highly inbred but genetically distant parasite lineages. Noteworthy, these discrete lineages remain stable over time and share recent ancestry with parasites at a large geographic distance. These results illustrate the power of genomic epidemiology approaches to map potential source parasite populations and prioritize areas for targeted control interventions to eliminate residual P. vivax transmission in the Amazon and similar endemic settings worldwide.

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