Occurrence of septuple and elevated Pfdhfr-Pfdhps quintuple mutations in a general population threatens the use of sulfadoxine-pyrimethamine for malaria prevention during pregnancy in eastern-coast of Tanzania

Efficacy of artemether-lumefantrine and dihydroartemisinin-piperaquine and prevalence of molecular markers of anti-malarial drug resistance in children in Togo in 2021

BACKGROUND

Artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) are the currently recommended first- and second-line therapies for uncomplicated Plasmodium falciparum infections in Togo. This study assessed the efficacy of these combinations, the proportion of Day3-positive patients (D3 +), the proportion of molecular markers associated with P. falciparum resistance to anti-malarial drugs, and the variable performance of HRP2-based malaria rapid diagnostic tests (RDTs).

METHODS

A single arm prospective study evaluating the efficacy of AL and DP was conducted at two sites (Kouvé and Anié) from September 2021 to January 2022. Eligible children were enrolled, randomly assigned to treatment at each site and followed up for 42 days after treatment initiation. The primary endpoint was polymerase chain reaction (PCR) adjusted adequate clinical and parasitological response (ACPR). At day 0, samples were analysed for mutations in the Pfkelch13, Pfcrt, Pfmdr-1, dhfr, dhps, and deletions in the hrp2/hrp3 genes.

RESULTS

A total of 179 and 178 children were included in the AL and DP groups, respectively. After PCR correction, cure rates of patients treated with AL were 97.5% (91.4-99.7) at day 28 in Kouvé and 98.6% (92.4-100) in Anié, whereas 96.4% (CI 95%: 89.1-98.8) and 97.3% (CI 95%: 89.5-99.3) were observed at day 42 in Kouvé and Anié, respectively. The cure rates of patients treated with DP at day 42 were 98.9% (CI 95%: 92.1-99.8) in Kouvé and 100% in Anié. The proportion of patients with parasites on day 3 (D3 +) was 8.5% in AL and 2.6% in DP groups in Anié and 4.3% in AL and 2.1% DP groups in Kouvé. Of the 357 day 0 samples, 99.2% carried the Pfkelch13 wild-type allele. Two isolates carried nonsynonymous mutations not known to be associated with artemisinin partial resistance (ART-R) (A578S and A557S). Most samples carried the Pfcrt wild-type allele (97.2%). The most common Pfmdr-1 allele was the single mutant 184F (75.6%). Among dhfr/dhps mutations, the quintuple mutant haplotype N51I/C59R/S108N + 437G/540E, which is responsible for SP treatment failure in adults and children, was not detected. Single deletions in hrp2 and hrp3 genes were detected in 1/357 (0.3%) and 1/357 (0.3%), respectively. Dual hrp2/hrp3 deletions, which could affect the performances of HRP2-based RDTs, were not observed.

CONCLUSION

The results of this study confirm that the AL and DP treatments are highly effective. The absence of the validated Pfkelch13 mutants in the study areas suggests the absence of ART -R, although a significant proportion of D3 + cases were found. The absence of dhfr/dhps quintuple or sextuple mutants (quintuple + 581G) supports the continued use of SP for IPTp during pregnancy and in combination with amodiaquine for seasonal malaria chemoprevention.

TRIAL REGISTRATION

ACTRN12623000344695.

Effectiveness of Intermittent Preventive Treatment with Sulfadoxine-Pyrimethamine in Pregnancy: Low Coverage and High Prevalence of Plasmodium falciparum dhfr-dhps Quintuple Mutants as Major Challenges in Douala, an Urban Setting in Cameroon

Intermittent preventive treatment in pregnancy with sulfadoxine and pyrimethamine (IPTp-SP) is a key component in the malaria control strategy implemented in Africa. The aim of this study was to determine IPTp-SP adherence and coverage, and the impact on maternal infection and birth outcomes in the context of widespread SP resistance in the city of Douala, Cameroon. Clinical and demographic information were documented among 888 pregnant women attending 3 health facilities, from the antenatal care visit to delivery. Positive samples were genotyped for P. falciparum gene (dhfr, dhps, and k13) mutations. The overall IPTp-SP coverage (≥three doses) was 17.5%, and 5.1% received no dose. P. falciparum prevalence was 16%, with a predominance of submicroscopic infections (89.3%). Malaria infection was significantly associated with locality and history of malaria, and it was reduced among women using indoor residual spraying. Optimal doses of IPTp-SP were significantly associated with reduced infection among newborns and women (secundiparous and multiparous), but there was no impact of IPTp-SP on the newborn bodyweight. Pfdhfr-Pfdhps quintuple mutants were over-represented (IRNI-FGKAA, IRNI-AGKAA), and sextuple mutants (IRNI-AGKAS, IRNI-FGEAA, IRNI-AGKGS) were also reported. The Pfk13 gene mutations associated with artemisinin resistance were not detected. This study highlights the role of ANC in achieving optimal SP coverage in pregnant women, the mitigated impact of IPTp-SP on malaria outcomes, and the high prevalence of multiple SP-resistant P. falciparum parasites in the city of Douala that could compromise the efficacy of IPTp-SP.

Molecular Determinants of Sulfadoxine-Pyrimethamine Resistance in Plasmodium falciparum Isolates from Central Africa between 2016 and 2021: Wide Geographic Spread of Highly Mutated Pfdhfr and Pfdhps Alleles

Sulfadoxine-pyrimethamine (SP) resistance impairs the efficacy of antimalarial drugs. Monitoring molecular markers in exported malaria infections provides an efficient way to trace the emergence of drug resistance in countries where malaria is endemic. Molecular markers in Pfdhfr and Pfdhps of 237 Plasmodium falciparum infections imported from central Africa between 2016 and 2021 were detected. The spatial and temporal distributions of Pfdhfr and Pfdhps mutations were analyzed. A high prevalence of Pfdhfr single-nucleotide polymorphisms (SNPs) (~92.34% to 99.10%) and a high frequency of the triple mutation haplotype I51R59N108 were observed. Cameroon, Equatorial Guinea, and Gabon showed a higher frequency (~96.61% to 100.00%) of I51R59N108 than other countries (~71.11% to 88.10%). The prevalence of C59R and I51R59N108 increased while that of other SNPs or haplotypes did not fluctuate greatly from 2016 to 2021. Large proportions of Pfdhps SNPs (A437G and K540E) were demonstrated. The SNP distribution of Pfdhps differed between countries, with S436A dominating in northern countries and A437G dominating in others. The proportions of I431V, A437G, and the triple mutant haplotype declined between 2016 and 2021, whereas the prevalence of the single mutant haplotype rose from 61.60% to 73.68%. Combinations of Pfdhfr-Pfdhps alleles conferring partial resistance, full resistance, and superresistance to SP, as defined in the text, were detected in 63.64%, 8.64%, and 0.91% of the samples, respectively. The octuple Pfdhfr-Pfdhps allele (I51R59N108-V431A436G437K540G581S613) was seen in 5.00% of the samples. We demonstrated the wide geographic spread and increasing trends in highly SP-resistant Pfdhfr genes and varying spatial patterns of Pfdhps mutants across countries in central Africa. The high prevalences of partially resistant, fully resistant, and superresistant Pfdhfr-Pfdhps combinations observed here indicated impaired SP efficacy. Increased molecular surveillance is required to monitor the changing status of the Pfdhfr and Pfdhps genes. IMPORTANCE Monitoring drug resistance is important for malaria control because its early detection enables timely action to prevent its spread and mitigate its impact. The wide geographic spread and the increasing trend of highly resistant Pfdhfr genes between 2016 and 2021 found in our study are worrisome and emphasize the urgency to monitor their updated status in central Africa. This study also illustrated the wide spread of the novel mutant Pfdhps I431V as well as the high prevalence of "partially resistant," "fully resistant," and "superresistant" Pfdhfr-Pfdhps combinations, indicating the urgent concern for SP efficacy in central Africa. These findings are alarming in central African countries where malaria is endemic, where SP was is widely used for the intermittent preventive treatment of malaria in pregnancy (IPTp) and the intermittent preventive treatment of malaria in infants below 5 years of age (IPTi), and urge enhanced molecular surveillance and responses to the threat of drug resistance.

The prevalence of molecular markers of resistance to sulfadoxine-pyrimethamine among pregnant women at first antenatal clinic attendance and delivery in the forest-savannah area of Ghana

Intermittent preventive treatment during pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) is used to prevent malaria and associated unfavorable maternal and foetal outcomes in pregnancy in moderate to high malaria transmission areas. Effectiveness of IPTp-SP is, however, threatened by mutations in the Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthase (Pfdhps) genes which confer resistance to pyrimethamine and sulfadoxine, respectively. This study determined the prevalence of molecular markers of SP resistance among pregnant women in a high malaria transmission area in the forest-savannah area of Ghana. Genomic DNA was extracted from 286 P. falciparum-positive dried blood spots obtained from pregnant women aged ≥18 years (255 at first Antenatal Care (ANC) clinic visit and 31 at delivery from 2017 to 2019) using Chelex 100. Mutations in Pfdhfr and Pfdhps genes were detected using molecular inversion probes and next generation sequencing. In the Pfdhfr gene, single nucleotide polymorphisms (SNPs) were detected in 83.1% (157/189), 92.0% (173/188) and 91.0% (171/188) at codons 51, 59, and 108 respectively in samples collected at first ANC visit, while SNPs were detected in 96.6 (28/29), 96.6% (28/29) and 96.8% (30/31) in isolates collected at delivery. The Pfdhfr triple mutant N51I, C59R and S108N (IRN) was carried by 80.5% (128/159) and 96.5% (28/29) of the typed isolates collected at ANC visit and at delivery respectively. In the Pfdhps gene, SNPs were detected in 0.6% (1/174), 76.2% (138/181), 33.2% (60/181), 1.2% (2/174), 0% (0/183), and 16.6% (27/173) at codons 431, 436, 437, 540, 581 and 613 respectively in samples collected at ANC, and 0% (0/25), 72% (18/25), 40% (10/25), 3.6% (1/25), 0% (0/29) and 7.4% (2/27) in samples collected at delivery. Quadruple mutant Pfdhfr N51I, C59R, and S108N + Pfdhps A437G (IRN-GK) was present in 25.8% (33/128) and 34.8% (8/23) of isolates at ANC and at delivery respectively. Quintuple mutant alleles Pfdhfr N51I, C59R, and S108N + Pfdhps A437G and K540E (IRN-GE) were detected in 0.8% (1/128) and 4.4% (1/23) of samples collected at ANC and at delivery respectively. No mutations were identified at Pfdhfr codons 16 or 164 or Pfdhps 581. There is a high prevalence of Pfdhfr triple mutant P. falciparum infections among pregnant women in the study area. However, prevalence of the combined Pfdhfr/Pfdhps quadruple and quintuple mutants IRN-GK and IRN-GE respectively prior to commencement of IPTp-SP were low, and no Pfdhps A581G mutant was detected, indicating that SP is still likely to be efficacious for IPTp-SP in the forest-savannah area in the middle belt of Ghana.

Artesunate-amodiaquine and artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in Liberia: in vivo efficacy and frequency of molecular markers

Background

Artesunate–amodiaquine (ASAQ) and Artemether–lumefantrine (AL) are the recommended treatment for uncomplicated Plasmodium falciparum malaria in Liberia. Intermittent preventive treatment with sulfadoxine/pyrimethamine is also recommended for pregnant women. The therapeutic efficacy of Artesunate–amodiaquine and Artemether–lumefantrine, and the frequency of molecular markers associated with anti-malarial drug resistance were investigated.

Methods

The therapeutic efficacy of ASAQ and AL was evaluated using the standard World Health Organization protocol (WHO. Methods for Surveillance of Antimalarial Drug Efficacy. Geneva: World Health Organization; 2009. https://www.who.int/malaria/publications/atoz/9789241597531/en/). Eligible children were recruited and monitored clinically and parasitologically for 28 days. Polymorphisms in the Pfkelch 13, chloroquine resistance transporter (Pfcrt), multidrug resistance 1 (Pfmdr-1), dihydrofolate reductase (Pfdhfr), and dihydropteroate synthase (Pfdhps) genes and copy number variations in the plasmepsin-2 (Pfpm2) gene were assessed in pretreatment samples.

Results

Of the 359 children enrolled, 180 were treated with ASAQ (89 in Saclepea and 91 in Bensonville) and 179 with AL (90 in Sinje and 89 in Kakata). Of the recruited children, 332 (92.5%) reached study endpoints. PCR-corrected per-protocol analysis showed ACPR of 90.2% (95% CI: 78.6–96.7%) in Bensonville and 92.7% (95% CI: 83.4.8–96.5%) in Saclepea for ASAQ, while ACPR of 100% was observed in Kakata and Sinje for AL. In both treatment groups, only two patients had parasites on day 3. No artemisinin resistance associated Pfkelch13 mutations or multiple copies of Pfpm2 were found. Most samples tested had the Pfcrt 76 T mutation (80/91, 87.9%), while the Pfmdr-1 86Y (40/91, 44%) and 184F (47/91, 51.6%) mutations were less frequent. The Pfdhfr triple mutant (51I/59R/108 N) was the predominant allele (49.2%). For the Pfdhps gene, it was the 540E mutant (16.0%), and the 436A mutant (14.3%). The quintuple allele (51I/59R/108 N-437G/540E) was detected in only one isolate (1/357).

Conclusion

This study reports a decline in the efficacy of ASAQ treatment, while AL remained highly effective, supporting the recent decision by NMCP to replace ASAQ with AL as first-line treatment for uncomplicated falciparum malaria. No association between the presence of the mutations in Pfcrt and Pfmdr-1 and the risk of parasite recrudescence in patients treated with ASAQ was observed. Parasites with signatures known to be associated with artemisinin and piperaquine resistance were not detected. The very low frequency of the quintuple Pfdhfr/Pfdhps mutant haplotype supports the continued use of SP for IPTp. Monitoring of efficacy and resistance markers of routinely used anti-malarials is necessary to inform malaria treatment policy.

Trial registration ACTRN12617001064392.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04140-7.

Effectiveness of Intermittent Preventive Treatment With Dihydroartemisinin-Piperaqunine Against Malaria in Pregnancy in Tanzania: A Randomized Controlled Trial

Intermittent preventive treatment in pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) to prevent malaria and adverse birth outcomes is threatened by Plasmodium falciparum resistance to sulfadoxine-pyrimethamine. We investigated the effectiveness of intermittent preventive treatment in pregnancy with monthly dihydroartemisinin-piperaquine (IPTp-DHP) as an alternative option to IPTp-SP. A total of 956 malaria-free (malaria rapid diagnostic test (MRDT) negative) pregnant women from moderate malaria transmission areas in Tanzania were enrolled and randomized to receive monthly IPTp-DHP (n = 478) or IPTp-SP (n = 478) and followed for maternal and birth outcomes. The primary outcome was the prevalence of histopathologically confirmed placental malaria (active or past infection). Secondary outcomes were overall malaria at delivery, symptomatic-malaria, parasitemia during pregnancy, and adverse birth outcomes as a composite of spontaneous-abortion, premature birth, stillbirth, and low birth weight (LBW) fetal anemia. Outcome differences between treatment groups were expressed as the protective efficacy (PE), defined as 1-prevalence ratios or 1-incidence rate ratio. The prevalence of histopathologically confirmed placental malaria was significantly lower in IPTp-DHP (2.5%, 12/478) than IPTp-SP (8.2%, 39/478); PE = 69% (95% confidence interval (CI): 42-84, P < 0.001). The prevalence of maternal malaria at delivery was significantly lower in IPTp-DHP (8.2%) than IPTp-SP (18.2%, P < 0.001). The incidence per person-years at risk for symptomatic-malaria (0.02 vs. 0.12, P = 0.002) and parasitemia during pregnancy (0.28 vs. 0.67, P < 0.001) were significantly lower in the IPTp-DHP group than in the IPTp-SP group. The prevalence of any adverse birth outcomes (composite) was not significantly (P = 0.06) different between IPTp-DHP (17.9%) and IPTp-SP (23.8%). However, the prevalence of LBW (4.6% vs. 9.6%, P = 0.003) was significantly lower in IPTp-DHP compared with IPTp-SP. We report superior protective efficacy of monthly IPTp-DHP against malaria in pregnancy and LBW than IPTp-SP.