Increasingly inbred and fragmented populations of Plasmodium vivax associated with the eastward decline in malaria transmission across the Southwest Pacific

The human malaria parasite Plasmodium vivax is more resistant to malaria control strategies than Plasmodium falciparum, and maintains high genetic diversity even when transmission is low. To investigate whether declining P. vivax transmission leads to increasing population structure that would facilitate elimination, we genotyped samples from across the Southwest Pacific region, which experiences an eastward decline in malaria transmission, as well as samples from two time points at one site (Tetere, Solomon Islands) during intensified malaria control. Analysis of 887 P. vivax microsatellite haplotypes from hyperendemic Papua New Guinea (PNG, n = 443), meso-hyperendemic Solomon Islands (n = 420), and hypoendemic Vanuatu (n = 24) revealed increasing population structure and multilocus linkage disequilibrium yet a modest decline in diversity as transmission decreases over space and time. In Solomon Islands, which has had sustained control efforts for 20 years, and Vanuatu, which has experienced sustained low transmission for many years, significant population structure was observed at different spatial scales. We conclude that control efforts will eventually impact P. vivax population structure and with sustained pressure, populations may eventually fragment into a limited number of clustered foci that could be targeted for elimination

Nationwide genetic surveillance of Plasmodium vivax in Papua New Guinea reveals heterogeneous transmission dynamics and routes of migration amongst subdivided populations

The Asia Pacific Leaders in Malaria Alliance (APLMA) have committed to eliminate malaria from the region by 2030. Papua New Guinea (PNG) has the highest malaria burden in the Asia-Pacific region but with the intensification of control efforts since 2005, transmission has been dramatically reduced and Plasmodium vivax is now the dominant malaria infection in some parts of the country. To gain a better understanding of the transmission dynamics and migration patterns of P. vivax in PNG, here we investigate population structure in eight geographically and ecologically distinct regions of the country. A total of 219 P. vivax isolates (16-30 per population) were successfully haplotyped using 10 microsatellite markers. A wide range of genetic diversity (He=0.37-0.87, Rs=3.60-7.58) and significant multilocus linkage disequilibrium (LD) was observed in six of the eight populations (IAS=0.08-0.15 p-value<0.05) reflecting a spectrum of transmission intensities across the country. Genetic differentiation between regions was evident (Jost's D=0.07-0.72), with increasing divergence of populations with geographic distance. Overall, P. vivax isolates clustered into three major genetic populations subdividing the Mainland lowland and coastal regions, the Islands and the Highlands. P. vivax gene flow follows major human migration routes, and there was higher gene flow amongst Mainland parasite populations than among Island populations. The Central Province (samples collected in villages close to the capital city, Port Moresby), acts as a sink for imported infections from the three major endemic areas. These insights into P. vivax transmission dynamics and population networks will inform targeted strategies to contain malaria infections and to prevent the spread of drug resistance in PNG

Relationship between transmission intensity and population genetic parameters for <i>Plasmodium vivax</i> populations of the Southwest Pacific.

<p>Diversity of parasite populations based on (A) mean gene diversity (<i>H</i>_s), (B) Allelic richness (<i>R</i>_s), (C) the proportion of closely related haplotype pairs (<i>P</i>s>0.50) and (D) multilocus linkage disequilibrium (<i>I</i>_A^S) was plotted against the proportion of polyclonal infections for each defined population (see <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0006146#pntd.0006146.t001" target="_blank">Table 1</a> and <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0006146#pntd.0006146.s003" target="_blank">S1 Table</a>).</p

Estimates of Multilocus Linkage Disequilibrium (LD) in <i>Plasmodium vivax</i> populations of the Southwest Pacific.

<p>Estimates of Multilocus Linkage Disequilibrium (LD) in <i>Plasmodium vivax</i> populations of the Southwest Pacific.</p

Phylogenetic analysis of <i>Plasmodium vivax</i> isolates of the Southwest Pacific.

<p>For the lower transmission regions of (A) Ngella and (B) Vanuatu, relatedness amongst haplotypes was defined by calculating the pairwise distance and visualized by drawing unrooted phylogenetic trees using the APE package in R software. Colours indicate the geographic origin of each sample as indicated in the key.</p

A framework for mapping and monitoring human-ocean interactions in near real-time during COVID-19 and beyond

The human response to the COVID-19 pandemic set in motion an unprecedented shift in human activity with unknown long-term effects. The impacts in marine systems are expected to be highly dynamic at local and global scales. However, in comparison to terrestrial ecosystems, we are not well-prepared to document these changes in marine and coastal environments. The problems are two-fold: 1) manual and siloed data collection and processing, and 2) reliance on marine professionals for observation and analysis. These problems are relevant beyond the pandemic and are a barrier to understanding rapidly evolving blue economies, the impacts of climate change, and the many other changes our modern-day oceans are undergoing. The “Our Ocean in COVID-19″ project, which aims to track human-ocean interactions throughout the pandemic, uses the new eOceans platform (eOceans.app) to overcome these barriers. Working at local scales, a global network of ocean scientists and citizen scientists are collaborating to monitor the ocean in near real-time. The purpose of this paper is to bring this project to the attention of the marine conservation community, researchers, and the public wanting to track changes in their area. As our team continues to grow, this project will provide important baselines and temporal patterns for ocean conservation, policy, and innovation as society transitions towards a new normal. It may also provide a proof-of-concept for real-time, collaborative ocean monitoring that breaks down silos between academia, government, and at-sea stakeholders to create a stronger and more democratic blue economy with communities more resilient to ocean and global change