Genetic polymorphism of merozoite surface protein 1 and antifolate-resistant genes in Plasmodium falciparum from Mali and Niger

Since 2015, countries in the Sahel region have implemented large-scale seasonal malaria chemoprevention (SMC). However, the mass use of sulfadoxine-pyrimethamine (SP) plus amodiaquine impacts the genetic diversity of malaria parasites and their sensitivity to antimalarials. This study aimed to describe and compare the genetic diversity and SP resistance of Plasmodium falciparum strains in Mali and Niger. We collected 400 blood samples in Mali and Niger from children aged 3-59 months suspected of malaria. Of them, 201 tested positive (Niger, 111, 55.2%; Mali, 90, 44.8%). Polymorphism of merozoite surface protein 1 (msp1) genetic marker showed 201 allotypes. The frequency of the RO33 allotype was significantly higher in Niger (63.6%) than in Mali (39.3%). There was no significant difference in the frequency of the K1 and MAD20 allotypes between the 2 countries. The multiplicity of infection was 2 allotypes per patient in Mali and one allotype per patient in Niger. The prevalence of strains with the triple mutants Pfdhfr51I/Pfdhfr59R/Pfdhps436A/F/H and Pfdhfr51I/Pfdhfr59R/Pfdhps437G was 18.1% and 30.2%, respectively, and 7.7% carried the quadruple mutant Pfdhfr51I/Pfdhfr59R/Pfdhps436A/F/H/Pfdhps437G. Despite the significant genetic diversity of parasite populations, the level of SP resistance was comparable between Mali and Niger. The frequency of mutations conferring resistance to SP still allows its effective use in intermittent preventive treatment in pregnant women and in SMC.

Plasmodium falciparum kelch13 polymorphisms identified after treatment failure with artemisinin-based combination therapy in Niger

BACKGROUND

Artemisinin-based combination therapy (ACT) is the most effective treatment for malaria, and has significantly reduced morbimortality. Polymorphisms associated with the Plasmodium falciparum Kelch gene (Pfkelch13) have been associated with delayed parasite clearance even with ACT treatment.

METHODS

The Pfkelch13 gene was sequenced from P. falciparum infected patients (n = 159) with uncomplicated malaria in Niger. An adequate clinical and parasitological response (ACPR) was reported in 155 patients. Four (n = 4) patients had treatment failure (TF) that were not reinfections-two of which had late parasitological failures (LPF) and two had late clinical failures (LCF).

RESULTS

Thirteen single nucleotide polymorphisms (SNPs) were identified of which seven were non-synonymous (C469R, T508S, R515T, A578S, I465V, I437V, F506L,), and three were synonymous (P443P, P715P, L514L). Three SNP (C469R, F506L, P715P) were present before ACT treatment, while seven mutations (C469R, T508S, R515T, L514L, P443P, I437V, I465V) were selected by artemether/lumefantrine (AL)-five of which were non-synonymous (C469R, T508S, R515T, I437V, I465V). Artesunate/amodiaquine (ASAQ) has selected any mutation. One sample presented three cumulatively non-synonymous SNPs-C469R, T508S, R515T.

CONCLUSIONS

This study demonstrates intra-host selection of Pfkelch13 gene by AL. The study highlights the importance of LCF and LPF parasites in the selection of resistance to ACT. Further studies using gene editing are required to confirm the potential implication of resistance to ACT with the most common R515T and T508S mutations. It would also be important to elucidate the role of cumulative mutations.

Countrywide insecticide resistance monitoring and first report of the presence of the L1014S knock down resistance in Niger, West Africa

BACKGROUND

Mass distribution of insecticide-treated nets (ITNs) is the principal malaria vector control strategy adopted by Niger. To better inform on the most appropriate ITN to distribute, the National Malaria Control Programme (NMCP) of Niger and its partners, conducted insecticide resistance monitoring in selected sites across the country.

METHODS

The susceptibility of Anopheles gambiae sensu lato (s.l.) to chlorfenapyr and pyrethroid insecticides was investigated in a total of sixteen sites in 2019 and 2020, using 2-5-day-old adults reared from wild collected larvae per site. The susceptibility status, pyrethroid resistance intensity at 5 and 10 times the diagnostic concentrations, and piperonyl butoxide (PBO) synergism with diagnostic concentrations of deltamethrin, permethrin and alpha-cypermethrin were assessed using WHO bioassays. Two doses (100 and 200 µg/bottle) of chlorfenapyr were tested using the CDC bottle assay method. Species composition and allele frequencies for knock-down resistance (kdr-L1014F and L1014S) and acetylcholinesterase (ace-1 G119S) mutations were further characterized using polymerase chain reaction (PCR).

RESULTS

High resistance intensity to all pyrethroids tested was observed in all sites except for alpha-cypermethrin in Gaya and Tessaoua and permethrin in Gaya in 2019 recording moderate resistance intensity. Similarly, Balleyara, Keita and Tillabery yielded moderate resistance intensity for alpha-cypermethrin and deltamethrin, and Niamey V low resistance intensity against deltamethrin and permethrin in 2020. Pre-exposure to PBO substantially increased susceptibility with average increases in mortality between 0 and 70% for tested pyrethroids. Susceptibility to chlorfenapyr (100 µg/bottle) was recorded in all sites except in Tessaoua and Magaria where susceptibility was recorded at the dose of 200 µg/bottle. Anopheles coluzzii was the predominant malaria vector species in most of the sites followed by An. gambiae sensu stricto (s.s.) and Anopheles arabiensis. The kdr-L1014S allele, investigated for the first time, was detected in the country. Both kdr-L1014F (frequencies [0.46-0.81]) and L1014S (frequencies [0.41-0.87]) were present in all sites while the ace-1 G119S was between 0.08 and 0.20.

CONCLUSION

The data collected will guide the NMCP in making evidence-based decisions to better adapt vector control strategies and insecticide resistance management in Niger, starting with mass distribution of new generation ITNs such as interceptor G2 and PBO ITNs.

Prevalence of Mutations in the Pfdhfr, Pfdhps, and Pfmdr1 Genes of Malarial Parasites Isolated from Symptomatic Patients in Dogondoutchi, Niger

The effectiveness of artemisinin-based combination therapies (ACTs) depends not only on that of artemisinin but also on that of partner molecules. This study aims to evaluate the prevalence of mutations in the Pfdhfr, Pfdhps, and Pfmdr1 genes from isolates collected during a clinical study. Plasmodium genomic DNA samples extracted from symptomatic malaria patients from Dogondoutchi, Niger, were sequenced by the Sanger method to determine mutations in the Pfdhfr (codons 51, 59, 108, and 164), Pfdhps (codons 436, 437, 540, 581, and 613), and Pfmdr1 (codons 86, 184, 1034, and 1246) genes. One hundred fifty-five (155) pre-treatment samples were sequenced for the Pfdhfr, Pfdhps, and Pfmdr1 genes. A high prevalence of mutations in the Pfdhfr gene was observed at the level of the N51I (84.97%), C59R (92.62%), and S108N (97.39%) codons. The key K540E mutation in the Pfdhps gene was not observed. Only one isolate was found to harbor a mutation at codon I431V. The most common mutation on the Pfmdr1 gene was Y184F in 71.43% of the mutations found, followed by N86Y in 10.20%. The triple-mutant haplotype N51I/C59R/S108N (IRN) was detected in 97% of the samples. Single-mutant (ICS and NCN) and double-mutant (IRS, NRN, and ICN) haplotypes were prevalent at 97% and 95%, respectively. Double-mutant haplotypes of the Pfdhps (581 and 613) and Pfmdr (86 and 184) were found in 3% and 25.45% of the isolates studied, respectively. The study focused on the molecular analysis of the sequencing of the Pfdhfr, Pfdhps, and Pfmdr1 genes. Although a high prevalence of mutations in the Pfdhfr gene have been observed, there is a lack of sulfadoxine pyrimethamine resistance. There is a high prevalence of mutation in the Pfmdr184 codon associated with resistance to amodiaquine. These data will be used by Niger’s National Malaria Control Program to better monitor the resistance of Plasmodium to partner molecules in artemisinin-based combination therapies.

[Malaria infection during pregnancy in Niamey, Niger]

Introduction

le paludisme chez la femme enceinte est un problème majeur de santé publique en Afrique. Il a des conséquences graves aussi bien sur la mère, le fœtus que le nouveau-né. Il est responsable d´un fort taux de morbi-mortalité maternelle et infantile. L´objectif de l´étude est de déterminer la prévalence de l´infection plasmodiale chez la femme enceinte, décrire ses signes cliniques et ses complications éventuelles, analyser les facteurs associés et proposer des mesures de prévention.

Méthodes

il s´agit d´une étude transversale, conduite du 1^er juin au 30 novembre 2017 à la Maternité Issaka Gazobi (MIG) de Niamey. Le diagnostic a été fait par microscopie.

Résultats

deux cents quarante-neuf (249) femmes ont été incluses dans cette étude. La prévalence de l´infection plasmodiale était de 36,5% (IC95%; [30,6; 42,9]). La densité parasitaire moyenne était de 177 P/μl (DS: 121; [40; 800]). Toutes les infections étaient à P. falciparum. Un peu plus de soixante-treize pourcent (73,6%). Seules 26,4% (24/91) ont fait un paludisme non compliqué ; 9,6% (6/91) ont avorté ; 38,4% des nouveau-nés avaient un faible poids à la naissance et 26,51% (66/249) ont développé un paludisme congénital. Le taux de létalité était de 1,1% (1/91). Le traitement préventif intermittent (TPI) protège significativement contre le paludisme gestationnel (p=0,01).

Conclusion

l´infection des femmes enceintes par le P. falciparum est très fréquente au Niger. Ce portage est le plus souvent asymptomatique mais peut évoluer vers un paludisme non compliqué ou même sévère. Les principales conséquences sont l´avortement, le faible poids à la naissance, le retard de croissance intra utero, le paludisme congénital et le décès maternel. Le TPI et l´utilisation de la moustiquaire imprégnée d´insecticide à longue durée d´action (MILDA) permettent de prévenir l´infection.

Transfusional Malaria and Associated Factors at the National Blood Transfusion Center of Niamey-Niger

SUMMARY

Problem. Transfusional malaria is an accidental transmission of Plasmodium via a blood transfusion. Its magnitude is underestimated and very little data on the assessment of this risk are available in Niger.

OBJECTIVE

This study aimed to determine the prevalence of plasmodial infection of blood bags at the National Blood Transfusion Center of Niamey (NBTC).

METHODOLOGY

A cross-sectional study to diagnose Plasmodium infection by microscopy and Rapid Diagnostic Test (RDT) was carried out during the rainy season (September to November 2015). Blood grouping was performed by the BETH-VINCENT technique.

RESULTS

One thousand three hundred and fifty-seven (1357) blood bags were collected. One hundred and fifty-seven (11.6%) of the donors were infected with Plasmodium by microscopy and 2.4% (9/369) by rapid diagnostic test. All infections were with P. falciparum (100%). The mean parasite density was 197 parasites/μL (SD=281; [80: 2000]). There were no significant differences in infection prevalence between the ABO blood groups (p = 0.3) or the rhesus positivity (p=08). There is also no significant difference in temporal (p = 0.1) and spatial (p = 0.6) distribution.

CONCLUSION

The transmission of transfusional malaria during the rainy season is a fact in Niger. Such risks were independent of the ABO blood type and positivity for the rhesus antigen. Pretransfusion diagnosis or posttransfusion therapy should be instituted to prevent it.

Efficacy of artesunate-amodiaquine, dihydroartemisinin-piperaquine and artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria in Maradi, Niger

BACKGROUND

Malaria endemic countries need to assess efficacy of anti-malarial treatments on a regular basis. Moreover, resistance to artemisinin that is established across mainland South-East Asia represents today a major threat to global health. Monitoring the efficacy of artemisinin-based combination therapies is of paramount importance to detect as early as possible the emergence of resistance in African countries that toll the highest burden of malaria morbidity and mortality.

METHODS

A WHO standard protocol was used to assess efficacy of the combinations artesunate-amodiaquine (AS-AQ Winthrop^®), dihydroartemisinin-piperaquine (DHA-PPQ, Eurartesim^®) and artemether-lumefantrine (AM-LM, Coartem^®) taken under supervision and respecting pharmaceutical recommendations. The study enrolled for each treatment arm 212 children aged 6-59 months living in Maradi (Niger) and suffering with uncomplicated falciparum malaria. The Kaplan-Meier 42-day PCR-adjusted cure rate was the primary outcome. A standardized parasite clearance estimator was used to assess delayed parasite clearance as surrogate maker of suspected artemisinin resistance.

RESULTS

No early treatment failures were found in any of the study treatment arms. The day-42 PCR-adjusted cure rate estimates were 99.5, 98.4 and 99.0% in the AS-AQ, DHA-PPQ and AM-LM arms, respectively. The reinfection rate (expressed also as Kaplan-Meier estimates) was higher in the AM-LM arm (32.4%) than in the AS-AQ (13.8%) and the DHA-PPQ arm (24.9%). The parasite clearance rate constant was 0.27, 0.26 and 0.25 per hour for AS-AQ, DHA-PPQ and AM-LM, respectively.

CONCLUSIONS

All the three treatments evaluated largely meet WHO criteria (at least 95% efficacy). AS-AQ and AL-LM may continue to be used and DHA-PPQ may be also recommended as first-line treatment for uncomplicated falciparum malaria in Maradi. The parasite clearance rate were consistent with reference values indicating no suspected artemisinin resistance. Nevertheless, the monitoring of anti-malarial drug efficacy should continue. Trial registration details Registry number at ClinicalTrial.gov: NCT01755559.