Molecular markers of resistance to amodiaquine plus sulfadoxine-pyrimethamine in an area with seasonal malaria chemoprevention in south central Niger.

BACKGROUND: In Niger, malaria transmission is markedly seasonal with most of the disease burden occurring in children during the rainy season. Seasonal malaria chemoprevention (SMC) with amodiaquine plus sulfadoxine-pyrimethamine (AQ + SP) is recommended in the country to be administered monthly just before and during the rainy season. Moreover, clinical decisions on use of SP for intermittent preventive treatment in pregnancy (IPTp) now depend upon the validated molecular markers for SP resistance in Plasmodium falciparum observed in the local parasite population. However, little is known about molecular markers of resistance for either SP or AQ in the south of Niger. To address this question, clinical samples which met clinical and biological criteria, were collected in Gabi, Madarounfa district, Maradi region, Niger in 2011-2012 (before SMC implementation). Molecular markers of resistance to pyrimethamine (pfdhfr), sulfadoxine (pfdhps) and amodiaquine (pfmdr1) were assessed by DNA sequencing. RESULTS: Prior to SMC implementation, the samples showed a high proportion of clinical samples that carried the pfdhfr 51I/59R/108N haplotype associated with resistance to pyrimethamine and pfdhps 436A/F/H and 437G mutations associated with reduced susceptibility to sulfadoxine. In contrast mutations in codons 581G, and 613S in the pfdhps gene, and in pfmdr1, 86Y, 184Y, 1042D and 1246Y associated with resistance to amodiaquine, were less frequently observed. Importantly, pfdhfr I164L and pfdhps K540E mutations shown to be the most clinically relevant markers for high level clinical resistance to SP were not detected in Gabi. CONCLUSIONS: Although parasites with genotypes associated with the highest levels of resistance to AQ + SP are not yet common in this setting, their importance for deployment of SMC and IPTp dictates that monitoring of these markers of resistance should accompany these interventions. This study also highlights the parasite heterogeneity within a small spatial area and the need to use caution when extrapolating results from surveys of molecular markers of resistance in a single site to inform regional policy decisions

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

Abstract 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: NCT0175555