Sampling for malaria molecular surveillance

Plasmodium falciparum molecular surveillance to inform the Mozambican National Malaria Control Programme strategy: protocol

INTRODUCTION

Malaria molecular surveillance has the potential to generate information on biological threats that compromise the effectiveness of antimalarial interventions. This study aims to streamline surveillance activities to inform the new strategic plan of the Mozambican National Malaria Control Programme (2023-2030) for malaria control and elimination.

METHODS AND ANALYSES

This prospective genomic surveillance study aims to generate Plasmodium falciparum genetic data to monitor diagnostic failures due to pfhrp2/3 deletions and molecular markers of antimalarial drug resistance, to characterise transmission sources and to inform the implementation of new antimalarial approaches to be introduced in Mozambique (chemoprevention and child malaria vaccination). The study, to be conducted between 2024 and 2026, will use three sampling schemes: a multicluster probabilistic health facility survey in the 10 provinces of the country to detect pfhrp2/3 deletions and markers of antimalarial drug resistance; dense sampling of all clinical cases in representative districts in the south targeted for elimination to characterise malaria importation and identify sources of transmission; and testing of pregnant women for malaria at their first antenatal care visit to assess malaria burden and molecular trends. Using a multiplex amplicon-based sequencing approach, the study will target microhaplotypes informative of genomic diversity and relatedness, as well as key drug resistance-associated genes, pfhrp2/3 deletion and malaria vaccine targets. Key genomic information will be visualised in a dashboard integrated into the District Health Information System V.2-based Malaria Information Storage System for programmatic use.

ETHICS AND DISSEMINATION

The protocol was reviewed and approved by the national ethics committee of Mozambique (Comité Nacional de Bioética para Saúde, Ref: 680/CNBS/23). Project results will be presented to all stakeholders using study-specific brochures and published in open-access journals.

TRIAL REGISTRATION NUMBER

NCT06529237.

Towards integrated malaria molecular surveillance in Africa

Integrated malaria molecular surveillance (iMMS) systems are essential for Africa's expanding malaria genomics initiatives. Here we highlight a few initiatives and demonstrate how iMMS can support evidence-based decisions and policies for National Malaria Programs and other malaria control stakeholders. We conclude with key considerations for advancing these malaria genomics initiatives towards sustainable iMMS.

Cost analyses for malaria molecular diagnosis for research planners in India and beyond

BACKGROUND

Malaria elimination mandates early and accurate diagnosis of infection. Although malaria diagnosis is programmatically dependent on microscopy/RDTs, molecular diagnosis has much better diagnostic accuracy. Higher cost of molecular diagnoses is a recognized challenge for use at the point of care. Because funding is always a recognized constraint, we performed financial cost-analyses of available molecular platforms for better utilization of available budget.

METHODS

Two strategies were applied to deduce the cost per sample. Strategy 1 included recurring components (RC) in minimum pack size, and biologist's time whereas strategy 2 included only RC and non-recurring components and costs are calculated for sample sizes (1-1,000,000) to infer the sample size effect.

RESULTS

Spin column-based manual DNA extraction (US$ 3.93 per sample) is the lowest-cost method, followed by magnetic bead-based automated, semi-automated, and PCI-based manual method. Further, DNA extraction cost per sample via spin column-based manual method and semi-automated method decreases with an increase in sample size up to 10,000. Real-time PCRs are ~ 2-fold more economical than conventional PCR, regardless of sample size.

CONCLUSIONS

This study is the first for malaria to estimate systematic molecular diagnosis financial costs. Kit-based and automated methods may replace conventional DNA extraction and amplification methods for a frugal high-throughput diagnosis.

Genomic malaria surveillance of antenatal care users detects reduced transmission following elimination interventions in Mozambique

Routine sampling of pregnant women at first antenatal care (ANC) visits could make Plasmodium falciparum genomic surveillance more cost-efficient and convenient in sub-Saharan Africa. We compare the genetic structure of parasite populations sampled from 289 first ANC users and 93 children from the community in Mozambique between 2015 and 2019. Samples are amplicon sequenced targeting 165 microhaplotypes and 15 drug resistance genes. Metrics of genetic diversity and relatedness, as well as the prevalence of drug resistance markers, are consistent between the two populations. In an area targeted for elimination, intra-host genetic diversity declines in both populations (p = 0.002-0.007), while for the ANC population, population genetic diversity is also lower (p = 0.0004), and genetic relatedness between infections is higher (p = 0.002) than control areas, indicating a recent reduction in the parasite population size. These results highlight the added value of genomic surveillance at ANC clinics to inform about changes in transmission beyond epidemiological data.

Molecular markers for malaria genetic epidemiology: progress and pitfalls

Over recent years, progress in molecular markers for genotyping malaria parasites has enabled informative studies of epidemiology and transmission dynamics. Results have highlighted the value of these tools for surveillance to support malaria control and elimination strategies. There are many different types and panels of markers available for malaria parasite genotyping, and for end users, the nuances of these markers with respect to 'use case', resolution, and accuracy, are not well defined. This review clarifies issues surrounding different molecular markers and their application to malaria control and elimination. We describe available marker panels, use cases, implications for different transmission settings, limitations, access, cost, and data accuracy. The information provided can be used as a guide for molecular epidemiology and surveillance of malaria.

Nanopore sequencing for malaria molecular surveillance: opportunities and challenges

Nanopore-based sequencing platforms offer the potential for affordable malaria molecular surveillance (MMS) in resource-limited settings to track and ultimately counteract emerging threats, such as drug resistance and diagnostic escape. Here, we discuss opportunities and challenges to implementing MMS using nanopore sequencing, highlighting priority areas for technical development and innovation.

Genomic malaria surveillance of antenatal care users detects reduced transmission following elimination interventions in Mozambique

Routine sampling of pregnant women at first antenatal care (ANC) visits could make Plasmodium falciparum genomic surveillance more cost-efficient and convenient in sub-Saharan Africa. We compared the genetic structure of parasite populations sampled from 289 first ANC attendees and 93 children from the community in Mozambique between 2015 and 2019. Samples were amplicon sequenced targeting 165 microhaplotypes and 15 drug resistance genes. Metrics of genetic diversity and relatedness, as well as the prevalence of drug resistance markers, were consistent between the two populations. In an area targeted for elimination, intra-host genetic diversity declined in both populations (p=0.002-0.007), while for the ANC population, population genetic diversity was also lower (p=0.0004), and genetic relatedness between infections were higher (p=0.002) than control areas, indicating a recent reduction in the parasite population size. These results highlight the added value of genomic surveillance at ANC clinics to inform about changes in transmission beyond epidemiological data.