Low risk of recurrence following artesunate-Sulphadoxine-pyrimethamine plus primaquine for uncomplicated Plasmodium falciparum and Plasmodium vivax infections in the Republic of the Sudan

Primaquine for uncomplicated Plasmodium vivax malaria in children younger than 15 years: a systematic review and individual patient data meta-analysis

BACKGROUND

Primaquine, the only widely available treatment to prevent relapsing Plasmodium vivax malaria, is produced as 15 mg tablets, and new paediatric formulations are being developed. To inform the optimal primaquine dosing regimen for children, we aimed to determine the efficacy and safety of different primaquine dose strategies in children younger than 15 years.

METHODS

We undertook a systematic review (Jan 1, 2000-July 26, 2024) for P vivax efficacy studies with at least one treatment group that was administered primaquine over multiple days, that enrolled children younger than 15 years, that followed up patients for at least 28 days, and that had data available for inclusion by June 30, 2022. Patients were excluded if they were aged 15 years or older, presented with severe malaria, received adjunctive antimalarials within 14 days of diagnosis, commenced primaquine more than 7 days after starting schizontocidal treatment, had a protocol violation in the original study, or were missing data on age, sex, or primaquine dose. Available individual patient data were collated and standardised. To evaluate efficacy, the risk of recurrent P vivax parasitaemia between days 7 and 180 was assessed by time-to-event analysis for different total mg/kg primaquine doses (low total dose of ∼3·5 mg/kg and high total dose of ∼7 mg/kg). To evaluate tolerability and safety, the following were assessed by daily mg/kg primaquine dose (low daily dose of ∼0·25 mg/kg, intermediate daily dose of ∼0·5 mg/kg, and high daily dose of ∼1 mg/kg): gastrointestinal symptoms (vomiting, anorexia, or diarrhoea) on days 5-7, haemoglobin decrease of at least 25% to less than 7g/dL (severe haemolysis), absolute change in haemoglobin from day 0 to days 2-3 or days 5-7, and any serious adverse events within 28 days. This study is registered with PROSPERO, CRD42021278085.

FINDINGS

In total, 3514 children from 27 studies and 15 countries were included. The cumulative incidence of recurrence by day 180 was 51·4% (95% CI 47·0-55·9) following treatment without primaquine, 16·0% (12·4-20·3) following a low total dose of primaquine, and 10·2% (8·4-12·3) following a high total dose of primaquine. The hazard of recurrent P vivax parasitaemia in children younger than 15 years was reduced following primaquine at low total doses (adjusted hazard ratio [HR] 0·17, 95% CI 0·11-0·25) and high total doses (0·09, 0·07-0·12), compared with no primaquine. In 525 children younger than 5 years, the relative rates of recurrence were also reduced, with an adjusted HR of 0·33 (95% CI 0·18-0·59) for a low total dose and 0·13 (0·08-0·21) for a high total dose of primaquine compared with no primaquine. The rate of recurrence following a high total dose was reduced compared with a low dose in children younger than 15 years (adjusted HR 0·54, 95% CI 0·35-0·85) and children younger than 5 years (0·41, 0·21-0·78). Compared with no primaquine, children treated with any dose of primaquine had a greater risk of gastrointestinal symptoms on days 5-7 after adjustment for confounders, with adjusted risks of 3·9% (95% CI 0-8·6) in children not treated with primaquine, 9·2% (0-18·7) with a low daily dose of primaquine, 6·8% (1·7-12·0) with an intermediate daily dose of primaquine, and 9·6% (4·8-14·3) with a high daily dose of primaquine. In children with 30% or higher glucose-6-phosphate dehydrogenase (G6PD) activity, there were few episodes of severe haemolysis following no primaquine (0·4%, 95% CI 0·1-1·5), a low daily dose (0·0%, 0·0-1·6), an intermediate daily dose (0·5%, 0·1-1·4), or a high daily dose (0·7%, 0·2-1·9). Of 15 possibly drug-related serious adverse events in children, two occurred following a low, four following an intermediate, and nine following a high daily dose of primaquine.

INTERPRETATION

A high total dose of primaquine was highly efficacious in reducing recurrent P vivax parasitaemia in children compared with a low dose, particularly in children younger than 5 years. In children treated with high and intermediate daily primaquine doses compared with low daily doses, there was no increase in gastrointestinal symptoms or haemolysis (in children with 30% or higher G6PD activity), but there were more serious adverse events.

FUNDING

Medicines for Malaria Venture, Bill & Melinda Gates Foundation, and Australian National Health and Medical Research Council.

Novel highly-multiplexed AmpliSeq targeted assay for Plasmodium vivax genetic surveillance use cases at multiple geographical scales

Although the power of genetic surveillance tools has been acknowledged widely, there is an urgent need in malaria endemic countries for feasible and cost-effective tools to implement in national malaria control programs (NMCPs) that can generate evidence to guide malaria control and elimination strategies, especially in the case of Plasmodium vivax. Several genetic surveillance applications ('use cases') have been identified to align research, technology development, and public health efforts, requiring different types of molecular markers. Here we present a new highly-multiplexed deep sequencing assay (Pv AmpliSeq). The assay targets the 33-SNP vivaxGEN-geo panel for country-level classification, and a newly designed 42-SNP within-country barcode for analysis of parasite dynamics in Vietnam and 11 putative drug resistance genes in a highly multiplexed NGS protocol with easy workflow, applicable for many different genetic surveillance use cases. The Pv AmpliSeq assay was validated using: 1) isolates from travelers and migrants in Belgium, and 2) routine collections of the national malaria control program at sentinel sites in Vietnam. The assay targets 229 amplicons and achieved a high depth of coverage (mean 595.7 ± 481) and high accuracy (mean error-rate of 0.013 ± 0.007). P. vivax parasites could be characterized from dried blood spots with a minimum of 5 parasites/µL and 10% of minority-clones. The assay achieved good spatial specificity for between-country prediction of origin using the 33-SNP vivaxGEN-geo panel that targets rare alleles specific for certain countries and regions. A high resolution for within-country diversity in Vietnam was achieved using the designed 42-SNP within-country barcode that targets common alleles (median MAF 0.34, range 0.01-0.49. Many variants were detected in (putative) drug resistance genes, with different predominant haplotypes in the pvmdr1 and pvcrt genes in different provinces in Vietnam. The capacity of the assay for high resolution identity-by-descent (IBD) analysis was demonstrated and identified a high rate of shared ancestry within Gia Lai Province in the Central Highlands of Vietnam, as well as between the coastal province of Binh Thuan and Lam Dong. Our approach performed well in geographically differentiating isolates at multiple spatial scales, detecting variants in putative resistance genes, and can be easily adjusted to suit the needs in other settings in a country or region. We prioritize making this tool available to researchers and NMCPs in endemic countries to increase ownership and ensure data usage for decision-making and malaria policy.

Prevalence of glucose-6-phosphate dehydrogenase deficiency (G6PDd), CareStart qualitative rapid diagnostic test performance, and genetic variants in two malaria-endemic areas in Sudan

Glucose-6-phosphate dehydrogenase deficiency (G6PDd) is the most common enzymopathy globally, and deficient individuals may experience severe hemolysis following treatment with 8-aminoquinolines. With increasing evidence of Plasmodium vivax infections throughout sub-Saharan Africa, there is a pressing need for population-level data at on the prevalence of G6PDd. Such evidence-based data will guide the expansion of primaquine and potentially tafenoquine for radical cure of P. vivax infections. This study aimed to quantify G6PDd prevalence in two geographically distinct areas in Sudan, and evaluating the performance of a qualitative CareStart rapid diagnostic test as a point-of-care test. Blood samples were analyzed from 491 unrelated healthy persons in two malaria-endemic sites in eastern and central Sudan. A pre-structured questionnaire was used which included demographic data, risk factors and treatment history. G6PD levels were measured using spectrophotometry (SPINREACT) and first-generation qualitative CareStart rapid tests. G6PD variants (202 G>A; 376 A>G) were determined by PCR/RFLP, with a subset confirmed by Sanger sequencing. The prevalence of G6PDd by spectrophotometry was 5.5% (27/491; at 30% of adjusted male median, AMM); 27.3% (134/491; at 70% of AMM); and 13.1% (64/490) by qualitative CareStart rapid diagnostic test. The first-generation CareStart rapid diagnostic test had an overall sensitivity of 81.5% (95%CI: 61.9 to 93.7) and negative predictive value of 98.8% (97.3 to 99.6). All persons genotyped across both study sites were wild type for the G6PD G202 variant. For G6PD A376G all participants in New Halfa had wild type AA (100%), while in Khartoum the AA polymorphism was found in 90.7%; AG in 2.5%; and GG in 6.8%. Phenotypic G6PD B was detected in 100% of tested participants in New Halfa while in Khartoum, the phenotypes observed were B (96.2%), A (2.8%), and AB (1%). The African A- phenotype was not detected in this study population. Overall, G6PDd prevalence in Sudan is low-to-moderate but highly heterogeneous. Point-of-care testing with the qualitative CareStart rapid diagnostic test demonstrated moderate performance with moderate sensitivity and specificity but high negative predicative value. The two sites harbored primarily the African B phenotype. A country-wide survey is recommended to understand GP6PD deficiencies more comprehensively in Sudan.

Current investigations on clinical pharmacology and therapeutics of Glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phospate dehydrogenase (G6PD) deficiency is estimated to affect more than 400 million people world-wide. This X-linked genetic deficiency puts stress on red blood cells (RBC), which may be further augmented under certain pathophysiological conditions and drug treatments. These conditions can cause hemolytic anemia and eventually lead to multi-organ failure and mortality. G6PD is involved in the rate-limiting step of the pentose phosphate pathway, which generates reduced nicotinamide adenine dinucleotide phosphate (NADPH). In RBCs, the NADPH/G6PD pathway is the only source for recycling reduced glutathione and provides protection from oxidative stress. Susceptibility of G6PD deficient populations to certain drug treatments and potential risks of hemolysis are important public health issues. A number of clinical trials are currently in progress investigating clinical factors associated with G6PD deficiency, validation of new diagnostic kits for G6PD deficiency, and evaluating drug safety, efficacy, and pathophysiology. More than 25 clinical studies in G6PD populations are currently in progress or have just been completed that have been examined for clinical pharmacology and potential therapeutic implications of G6PD deficiency. The information on clinical conditions, interventions, purpose, outcome, and status of these clinical trials has been studied. A critical review of ongoing clinical investigations on pharmacology and therapeutics of G6PD deficiency should be highly important for researchers, clinical pharmacologists, pharmaceutical companies, and global public health agencies. The information may be useful for developing strategies for treatment and control of hemolytic crisis and potential drug toxicities in G6PD deficient patients.

Primaquine alternative dosing schedules for preventing malaria relapse in people with Plasmodium vivax

BACKGROUND

Plasmodium vivax liver stages (hypnozoites) may cause relapses, prolonging morbidity, and impeding malaria control and elimination. The World Health Organization (WHO) recommends three schedules for primaquine: 0.25 mg/kg/day (standard), or 0.5 mg/kg/day (high standard) for 14 days, or 0.75 mg/kg once weekly for eight weeks, all of which can be difficult to complete. Since primaquine can cause haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, clinicians may be reluctant to prescribe primaquine without G6PD testing, and recommendations when G6PD status is unknown must be based on an assessment of the risks and benefits of prescribing primaquine. Alternative safe and efficacious regimens are needed.

OBJECTIVES

To assess the efficacy and safety of alternative primaquine regimens for radical cure of P vivax malaria compared to the standard or high-standard 14-day courses.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE (PubMed); Embase (Ovid); LILACS (BIREME); WHO International Clinical Trials Registry Platform and ClinicalTrials.gov up to 2 September 2019, and checked the reference lists of all identified studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of adults and children with P vivax malaria using either chloroquine or artemisinin-based combination therapy plus primaquine at a total adult dose of at least 210 mg, compared with the WHO-recommended regimens of 0.25 or 0.5 mg/kg/day for 14 days.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and quality, and extracted data. We calculated risk ratios (RRs) with 95% confidence intervals (CIs) for dichotomous data. We grouped efficacy data according to length of follow-up, partner drug, and trial location. We analysed safety data where included.

MAIN RESULTS

0.5 mg/kg/day for seven days versus standard 0.25 mg/kg/day for 14 days There may be little or no difference in P vivax recurrences at six to seven months when using the same total dose (210 mg adult dose) over seven days compared to 14 days (RR 0.96, 95% CI 0.66 to 1.39; 4 RCTs, 1211 participants; low-certainty evidence). No serious adverse events were reported. We do not know if there is any difference in the number of adverse events resulting in discontinuation of primaquine (RR 1.04, 95% CI 0.15 to 7.38; 5 RCTs, 1427 participants) or in the frequency of anaemia (RR 3.00, 95% CI 0.12 to 72.91, 1 RCT, 240 participants) between the shorter and longer regimens (very low-certainty evidence). Three trials excluded people with G6PD deficiency; two did not provide this information. Pregnant and lactating women were either excluded or no details were provided. High-standard 0.5 mg/kg/day for 14 days versus standard 0.25 mg/kg/day for 14 days There may be little or no difference in P vivax recurrences at six months with 0.5 mg/kg/day primaquine for 14 days compared to 0.25 mg/kg/day for 14 days (RR 0.84 (95% CI 0.49 to 1.43; 2 RCTs, 677 participants, low-certainty evidence). No serious adverse events were reported. We do not know whether there is a difference in adverse events resulting in discontinuation of treatment with the high-standard dosage (RR 4.19, 95% CI 0.90 to 19.60; 1 RCT, 778 participants, very low-certainty evidence). People with G6PD deficiency and pregnant or lactating women were excluded. 0.75 mg/kg/week for eight weeks versus high-standard 0.5 mg/kg/day for 14 days We do not know whether weekly primaquine increases or decreases recurrences of P vivax compared to high-standard 0.5 mg/kg/day for 14 days, at 11 months' follow-up (RR 3.18, 95% CI 0.37 to 27.60; 1 RCT, 122 participants; very low-certainty evidence). No serious adverse events and no episodes of anaemia were reported. G6PD-deficient patients were not randomized but included in the weekly primaquine group (only one patient detected). 1 mg/kg/day for seven days versus high standard 0.5 mg/kg/day for 14 days There is probably little or no difference in P vivax recurrences at 12 months between 1.0 mg/kg/day primaquine for seven days and the high-standard 0.5 mg/kg/day for 14 days (RR 1.03, 95% CI 0.82 to 1.30; 2 RCTs, 2526 participants; moderate-certainty evidence). There may be moderate to large increase in serious adverse events in the 1.0 mg/kg/day primaquine for seven days compared with the high-standard 0.5 mg/kg/day for 14 days, during 42 days follow-up (RR 12.03, 95% CI 1.57 to 92.30; 1 RCT, 1872 participants, low-certainty evidence). We do not know if there is a difference between 1.0 mg/kg/day primaquine for seven days and high-standard 0.5 mg/kg/day for 14 days in adverse events that resulted in discontinuation of treatment (RR 2.50, 95% CI 0.49 to 12.87; 1 RCT, 2526 participants, very low-certainty evidence), nor if there is difference in frequency of anaemia by 42 days (RR 0.93, 95% CI 0.62 to 1.41; 2 RCTs, 2440 participants, very low-certainty evidence). People with G6PD deficiency were excluded. Other regimens Two RCTs evaluated other rarely-used doses of primaquine, one of which had very high loss to follow-up. Adverse events were not reported. People with G6PD deficiency and pregnant or lactating women were excluded.

AUTHORS' CONCLUSIONS

Trials available to date do not detect a difference in recurrence between the following regimens: 1) 0.5 mg/kg/day for seven days versus standard 0.25 mg/kg/day for 14 days; 2) high-standard 0.5 mg/kg/day for 14 days versus standard 0.25 mg/kg/day for 14 days; 3) 0.75 mg/kg/week for eight weeks versus high-standard 0.5 mg/kg/day for 14 days; 4) 1 mg/kg/day for seven days versus high-standard 0.5 mg/kg/day for 14 days. There were no differences detected in adverse events for Comparisons 1, 2 or 3, but there may be more serious adverse events with the high seven-day course in Comparison 4. The shorter regimen of 0.5 mg/kg/day for seven days versus standard 0.25 mg/kg/day for 14 days may suit G6PD-normal patients. Further research will help increase the certainty of the findings and applicability in different settings.

Genetic polymorphism of the N-terminal region in circumsporozoite surface protein of Plasmodium falciparum field isolates from Sudan

Background

Malaria caused by Plasmodium falciparum parasite is still known to be one of the most significant public health problems in sub-Saharan Africa. Genetic diversity of the Sudanese P. falciparum based on the diversity in the circumsporozoite surface protein (PfCSP) has not been previously studied. Therefore, this study aimed to investigate the genetic diversity of the N-terminal region of the pfcsp gene.

Methods

A cross-sectional molecular study was conducted; 50 blood samples have been analysed from different regions in Sudan. Patients were recruited from the health facilities of Khartoum, New Halfa, Red Sea, White Nile, Al Qadarif, Gezira, River Nile, and Ad Damazin during malaria transmission seasons between June to October and December to February 2017–2018. Microscopic and nested PCR was performed for detection of P. falciparum. Merozoite surface protein-1 was performed to differentiate single and multiple clonal infections. The N-terminal of the pfcsp gene has been sequenced using PCR-Sanger dideoxy method and analysed to sequences polymorphism including the numbers of haplotypes (H), segregating sites (S), haplotypes diversity (Hd) and the average number of nucleotide differences between two sequences (Pi) were obtained using the software DnaSP v5.10. As well as neutrality testing, Tajima’s D test, Fu and Li’s D and F statistics.

Results

PCR amplification resulted in 1200 bp of the pfcsp gene. Only 21 PCR products were successfully sequenced while 29 were presenting multiple clonal P. falciparum parasite were not sequenced. The analysis of the N-terminal region of the PfCSP amino acids sequence compared to the reference strains showed five different haplotypes. H1 consisted of 3D7, NF54, HB3 and 13 isolates of the Sudanese pfcsp. H2 comprised of 7G8, Dd2, MAD20, RO33, Wellcome strain, and 5 isolates of the Sudanese pfcsp. H3, H4, and H5 were found in 3 distinct isolates. Hd was 0.594 ± 0.065, and S was 12. The most common polymorphic site was A98G; other sites were D82Y, N83H, N83M, K85L, L86F, R87L, R87F, and A98S. Fu and Li’s D* test value was − 2.70818, Fu and Li’s F* test value was − 2.83907, indicating a role of negative balancing selection in the pfcsp N-terminal region. Analysis with the global pfcsp N-terminal regions showed the presence of 13 haplotypes. Haplotypes frequencies were 79.4%, 17.0%, 1.6% and 1.0% for H1, H2, H3 and H4, respectively. Remaining haplotypes frequency was 0.1% for each. Hd was 0.340 ± 0.017 with a Pi of 0.00485, S was 18 sites, and Pi was 0.00030. Amino acid polymorphisms identified in the N-terminal region of global pfcsp were present at eight positions (D82Y, N83H/M, K85L/T/N, L86F, R87L/F, A98G/V/S, D99G, and G100D).

Conclusions

Sudanese pfcsp N-terminal region was well-conserved with only a few polymorphic sites. Geographical distribution of genetic diversity showed high similarity to the African isolates, and this will help and contribute in the deployment of RTS,S, a PfCSP-based vaccine, in Sudan.