Limited differentiation among Plasmodium vivax populations from the northwest and to the south Pacific Coast of Colombia: A malaria corridor?

PLoS Negl Trop Dis. 2019 Mar 28;13(3):e0007310. doi: 10.1371/journal.pntd.0007310. eCollection 2019 Mar.

Abstract

Background: Malaria remains endemic in several countries of South America with low to moderate transmission intensity. Regional human migration through underserved endemic areas may be responsible for significant parasite dispersion making the disease resilient to interventions. Thus, the genetic characterization of malarial parasites is an important tool to assess how endemic areas may connect via the movement of infected individuals. Here, four sites in geographically separated areas reporting 80% of the malaria morbidity in Colombia were studied. The sites are located on an imaginary transect line of 1,500 km from the northwest to the south Pacific Coast of Colombia with a minimal distance of 500 km between populations that display noticeable ethnic, economic, epidemiological, and ecological differences.

Methodology/principal findings: A total of 624 Plasmodium vivax samples from the four populations were genotyped by using eight microsatellite loci. Although a strong geographic structure was expected between these populations, only moderate evidence of genetic differentiation was observed using a suite of population genetic analyses. High genetic diversity, shared alleles, and low linkage disequilibrium were also found in these P. vivax populations providing no evidence for a bottleneck or clonal expansions as expected from recent reductions in the transmission that could have been the result of scaling up interventions or environmental changes. These patterns are consistent with a disease that is not only endemic in each site but also imply that there is gene flow among these populations across 1,500 km.

Conclusion /significance: The observed patterns in P. vivax are consistent with a "corridor" where connected endemic areas can sustain a high level of genetic diversity locally and can restore parasite-subdivided populations via migration of infected individuals even after local interventions achieved a substantial reduction of clinical cases. The consequences of these findings in terms of control and elimination are discussed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Bayes Theorem
  • Cluster Analysis
  • Colombia / epidemiology
  • Endemic Diseases*
  • Epidemiological Monitoring
  • Gene Frequency
  • Genetic Variation*
  • Genetics, Population*
  • Genotype
  • Geography
  • Humans
  • Linkage Disequilibrium
  • Malaria, Vivax / epidemiology*
  • Malaria, Vivax / parasitology
  • Malaria, Vivax / prevention & control
  • Microsatellite Repeats / genetics
  • Plasmodium vivax / genetics*
  • Plasmodium vivax / isolation & purification

Grants and funding

This work was supported by grants from the US National Institutes of Health (NIAID/ICEMR U19AI089702 to SH, R56AI109416 to AE; https://www.nih.gov/), Colciencias (360-2011 to MAH, 458-2012 to MAH, 719-2013 to SH; http://www.colciencias.gov.co/), and the Colombian Presidential Agency of International Cooperation (045-2013 to SH; http://www.apccolombia.gov.co/). This research was conducted at sites corresponding to Centro Latino Americano de Investigación en Malaria (CLAIM). Computer resources were provided by a grant from the Pennsylvania Department of Health (TU-420721). The funders had no role in study design, data collection, and analysis, decision to publish, or preparation of the manuscript.