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.

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]. / Infection palustre de la femme enceinte à Niamey au Niger.

INTRODUCTION: malaria during pregnancy is a major public health problem in Africa. It can have serious consequences for mother, fetus and newborn. It is associated with high maternal and infant mortality rate. The purpose of our study was to determine the prevalence of plasmodium infection in pregnant women, describe their clinical signs and potential complications, analyze associated factors, and propose preventive measures. METHODS: we conducted a cross-sectional study at the Issaka Gazobi Maternity Ward (MIG), Niamey, from 1 June to 30 November 2017. Diagnosis was based on microscopic examination. RESULTS: two hundred and forty-nine (249) women were included in this study. The prevalence of plasmodium infection was 36.5% (IC95%; [30.6; 42.9]). Mean parasite density was 177 P/µl (SD: 121; [40; 800]). All infections were due to P. falciparum. Seventy-three point six percent (67/91) of infected women were asymptomatic. Only 26.4% (24/91) of them had uncomplicated malaria; 9.6% (6/91) had miscarriage; 38.4% of newborns were low birthweight; 26.51% (66/249) developed congenital malaria. Mortality rate was 1.1% (1/ 91). Intermittent preventive treatment (IPT) significantly protected patients against gestational malaria (p=0.01). CONCLUSION: in Niger, P. falciparum infection very commonly affects pregnant women. It is most often asymptomatic but it can lead to uncomplicated or even severe malaria. Main consequences include abortion, low birth weight, intrauterine growth retardation, congenital malaria and maternal death. IPT and the use of long-lasting insecticide-treated mosquito nets (LLINs) can prevent 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.

Etude du polymorphisme génétique des souches de plasmodium falciparum au Niger

Problématique : Le paludisme à Plasmodium falciparum est un problème majeur de santé publique au Niger. Plasmodium falciparum est l'agent responsable de 97% des cas de paludisme. Il est aussi responsable des formes cliniques graves comme le neuropaludisme et l'anémie sévère.Pour évaluer l'impact des stratégies de lutte contre le paludisme sur la diversité génétique, nous avons caractérisé les populations parasitaires du Niger en amplifiant le block2 du gène msp1 et la région variable centrale du gène msp2. Des amorces spécifiques des différentes familles allèliques (K1, MAD20 et RO33 pour msp1) puis (3D7 et FC27 pour msp2) ont permis de distinguer les allèles du gène msp1 et du gène msp2.Objectif général : L'objectif est d'analyser la diversité génétique et la complexité des infections à P.falciparum au niveau de 13 sites représentatifs de la situation épidémiologique du paludisme au Niger.Résultat : 510 échantillons de 13 sites du Niger ont été génotypés. Une très grande diversité génétique est observée avec les deux marqueurs. En effet, il y'a 17 allèles différents de type msp1 et 14 allèles différents de type msp2. La famille allélique la plus fréquente dans la population est 3D7 (63%) suivie de K1 (43.2%). Les familles alléliques les plus rares sont MAD 20 (28.4%) et RO33 (28.4%). La distribution allélique des gènes msp1 et msp2 est très variée selon le site. Le nombre de clones varie de 1 à 5 par patient. 23% des infections sont polyclonales. La multiplicité des infections (MOI) est de 2.8 au Niger. Il y'a une différence significative de MOI selon les sites (p<0.05). Nos résultats sont discutés selon la latitude et la longitude des sites puis au regard d'études semblables en Afrique de l'ouest.Conclusion : La diversité génétique et la complexité des infections dépendent du niveau de transmission du paludisme. La relation entre la multiplicité des infections et la transmission n'est pas linéaire. Des facteurs écologiques et environnementaux comme la disponibilité en eau de surface et l'humidité relative interviennent