K13-propeller gene polymorphisms in Plasmodium falciparum parasite population: a systematic review protocol of burden and associated factors

Historical experiences on mass drug administration for malaria control and elimination, its challenges and China's experience: a narrative review

After decades of efforts, malaria is still a major public health problem in many countries, especially in sub-Saharan Africa. Mass drug administration (MDA) has been one of the interventions used to control malaria. China, the largest and most populous country in the world, has recently achieved malaria elimination with MDA within its strategy. Therefore, knowing the history of the use of MDA, and its advantages and challenges are crucial to better implement MDA as a component of malaria control and elimination strategy. This narrative review focused on the use of MDA from the past to present, the experiences of successful and failed MDA interventions to control malaria in Africa, Asia, and South Pacific region, the challenges faced, as well as China's experience in malaria control and elimination. A direct search using key words and phrases was conducted using the web search engines Google and Google Scholar, peer-reviewed journal websites and PubMed database to mainly screen articles on MDA studies with positive and negative results, the World Health Organization guidelines, and other MDA-related reports. We also summarized our historical field experiences on MDA in malaria control to provide informed perspective on the challenges of MDA. Following the spirit of innovation, a comprehensive strategy with MDA at its core and each additional measure compensating one another's shortage based on different malaria transmission settings and stratification could be the highlight of future malaria control and elimination strategy to help achieve the vision of a malaria-free world.

Association of Plasmodium falciparum kelch13 R561H genotypes with delayed parasite clearance in Rwanda: an open-label, single-arm, multicentre, therapeutic efficacy study

BACKGROUND

Partial artemisinin resistance is suspected if delayed parasite clearance (ie, persistence of parasitaemia on day 3 after treatment initiation) is observed. Validated markers of artemisinin partial resistance in southeast Asia, Plasmodium falciparum kelch13 (Pfkelch13) R561H and P574L, have been reported in Rwanda but no association with parasite clearance has been observed. We aimed to establish the efficacy of artemether-lumefantrine and genetic characterisation of Pfkelch13 alleles and their association with treatment outcomes.

METHODS

This open-label, single-arm, multicentre, therapeutic efficacy study was done in 2018 in three Rwandan sites: Masaka, Rukara, and Bugarama. Children aged 6-59 months with P falciparum monoinfection and fever were eligible and treated with a 3-day course of artemether-lumefantrine. Treatment response was monitored for 28 days using weekly microscopy screenings of blood samples for P falciparum. Mutations in Pfkelch13 and P falciparum multidrug resistance-1 (Pfmdr1) genes were characterised in parasites collected from enrolled participants. Analysis of flanking microsatellites surrounding Pfkelch13 was done to define the origins of the R561H mutations. The primary endpoint was PCR-corrected parasitological cure on day 28, as per WHO protocol.

FINDINGS

228 participants were enrolled and 224 (98·2%) reached the study endpoint. PCR-corrected efficacies were 97·0% (95% CI 88-100) in Masaka, 93·8% (85-98) in Rukara, and 97·2% (91-100) in Bugarama. Pfkelch13 R561H mutations were present in 28 (13%) of 218 pre-treatment samples and P574L mutations were present in two (1%) pre-treatment samples. 217 (90%) of the 240 Pfmdr1 haplotypes observed in the pretreatment samples, had either the NFD (N86Y, Y184F, D1246Y) or NYD haplotype. Eight (16%) of 51 participants in Masaka and 12 (15%) of 82 participants in Rukara were microscopically positive 3 days after treatment initiation, which was associated with pre-treatment presence of Pfkelch13 R561H in Masaka (p=0·0005). Genetic analysis of Pfkelch13 R561H mutations suggest their common ancestry and local origin in Rwanda.

INTERPRETATION

We confirm evidence of emerging artemisinin partial resistance in Rwanda. Although artemether-lumefantrine remains efficacious, vigilance for decreasing efficacy, further characterisation of artemisinin partial resistance, and evaluation of additional antimalarials in Rwanda should be considered.

FUNDING

The US President's Malaria Initiative.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Different Plasmodium falciparum clearance times in two Malian villages following artesunate monotherapy

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High prevalence of residual parasitemia at day 3 post-artesunate monotherapy treatment using qPCR while no parasites were detected by microscopy at the same timepoint.

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A longer parasite clearance time observed in a Malian village.

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Artesunate treatment is still efficacious on Plasmodium falciparum in Mali.

Background

Artemisinin resistance described as increased parasite clearance time (PCT) is rare in Africa. More sensitive methods such as qPCR might better characterize the clearance phenotype in sub-Saharan Africa.

Methods

PCT is explored in Mali using light microscopy and qPCR after artesunate for uncomplicated malaria. In two villages, patients were followed for 28 days. Blood smears and spots were collected respectively for microscopy and qPCR. Parasitemia slope half-life was calculated after microscopy. Patient residual parasitemia were measured by qPCR.

Results

Uncorrected adequate clinical and parasitological responses (ACPR) observed in Faladje and Bougoula-Hameau were 78% and 92%, respectively (p = 0.01). This reached 100% for both after molecular correction.

Proportions of 24H microscopy positive patients in Faladje and Bougoula-Hameau were 97.2% and 72%, respectively (p < 0.0001).

Slope half-life was 2.8 h in Faladje vs 2H in Bougoula-Hameau (p < 0.001) and

Proportions of 72H patients with residual parasitemia were 68.5% and 40% in Faladje and Bougoula-Hameau, respectively (p = 0.003). The mean residual parasitemia was 2.9 in Faladje vs. 0.008 in Bougoula-Hameau (p = 0.002).

Although artesunate is efficacious in Mali, the longer parasite clearance time with submicroscopic parasitemia observed may represent early signs of developing P. falciparum resistance to artemisinins.

K13-propeller gene polymorphisms in Plasmodium falciparum parasite population in malaria affected countries: a systematic review of prevalence and risk factors

Background

Efficacy of artemisinin (ART) agents, a critical element of current malaria control efforts is threatened by emergence and spread of resistance. Mutations in pfkelch13 gene associated with ART-resistance evolved in Southeast Asia (SEA). k13 mutations whose role in ART-resistance remains unknown, have subsequently emerged independently across all malaria-affected regions. The aim of this systematic review was to determine the prevalence and identify risk factors of Plasmodium falciparum k13 mutations in malaria-endemic countries.

Methods

An electronic search of studies from 2014 to date was done in MEDLINE via PubMED, SCOPUS, EMBASE and LILACS/VHL databases. Mesh terms and Boolean operators (AND, OR) were used. Two librarians independently conducted this search (RS and AK). The articles were screened for inclusion using a priori criteria set following PRISMA-P and STREGA guidelines. Three independent reviewers (NL, BB, and OM) extracted the data. Data analysis was performed in Open Meta Analyst software. Random effects analysis (DL) was used and heterogeneity established using I²-statistic.

Results

A total of 482 articles were retrieved from Pubmed = 302, Lilacs/Vhl = 50, Embase = 80, and Scopus = 37; Bibliography/other searches = 13, of which 374 did not meet the inclusion criteria. The aggregate prevalence of single nucleotide polymorphisms (SNPs) in pfkelch13 gene was 27.6% (3694/14,827) (95% CI 22.9%, 32.3%). Sub-group analysis showed that aggregate prevalence of non-synonymous SNPs in pfkelch13 gene was higher, 45.4% (95% CI 35.4%, 55.3%) in Southeast Asia as opposed to 7.6% (95% CI 5.6%, 9.5%) in the African region. A total of 165 independent k13 mutations were identified across malaria-affected regions globally. A total of 16 non-validated k13 mutations were associated with increased ART parasite clearance half-life (t_1/2 > 5 h). The majority, 45.5% (75/165), of the mutations were reported in single P. falciparum parasite infections. Of the 165 k13-mutations, over half were reported as new alleles. Twenty (20) non-propeller mutations in the pfkelch13 gene were identified.

Conclusion

This review identified emergence of potential ART-resistance mediating k13 mutations in the African region. Diversity of mutations in pfkelch13 gene is highest in African region compared to SEA. Mutations outside the pfkelch13 propeller region associated with increased ART parasite clearance half-life occur in malaria-affected regions.