Trends ofPlasmodium falciparummolecular markers associated with resistance to artemisinins and reduced susceptibility to lumefantrine in Mainland Tanzania from 2016 to 2021

Abstract

AbstractBackgroundTherapeutic efficacy studies (TESs) and detection of molecular markers of drug resistance are recommended by the World Health Organization (WHO) to monitor the efficacy of artemis inin combination therapy (ACT). This study assessed the trends of molecular markers of artemis inin resistance and/or reduced susceptibility to lumefantrine using samples collected in TES conducted in Mainland Tanzania from 2016 to 2021.MethodsA total of 2,015 samples were collected during TES of artemether-lumefantrine at eight sentinel sites (in Kigoma, Mbeya, Morogoro, Mtwara, Mwanza, Pwani, Tabora, and Tanga regions) between 2016 and 2021. Photo-induced electron transfer polymerase chain reaction (PET-PCR) was used to confirm presence of malaria parasites before capillary sequencing, which targeted two genes:Plasmodium falciparumkelch 13 propeller domain (k13) andP. falciparummultidrug resistance 1 (pfmdr1).ResultsSequencing success was ≥87.8%, and 1,724/1,769 (97.5%)k13wild-type samples were detected. Thirty-seven (2.1%) samples had synonymous mutations and only eight (0.4%) had non-synonymous mutations in thek13gene; seven of these were not validated by WHO as molecular markers of resistance (I416V, E433D, R471S, P475S, A578S, and Q613E). One sample from Morogoro in 2020 had ak13R622Imutation, which is a validated marker of artemisinin partial resistance. Forpfmdr1,all except two samples carried N86 (wild-type), while mutations at Y184Fincreased from 33.9% in 2016 to about 60.5% in 2021, and only four samples (0.2%) had D1246Ymutations.pfmdr1haplotypes were reported in 1,711 samples, with 985 (57.6%) NYD, 720 (42.1%) NFD, and six (0.4%) carrying minor haplotypes (three with NYY, 0.2%; YFD in two, 0.1%; and NFYin one sample, 0.1%). Between 2016 and 2021, NYD decreased from 66.1% to 45.2%, while NFD increased from 38.5% to 54.7%.ConclusionThis is the first report of the R622I (k13 validated mutation) in Tanzania. N86 and D1246 were nearly fixed, while increases in Y184Fmutations and NFD haplotype were observed between 2016 and 2021. Despite the reports of ART-R in Rwanda and Uganda, this study did not report any other validated mutations in these study sites in Tanzania apart from R622I suggesting that intensified surveillance is urgently needed to monitor trends of drug resistance markers and their impact on the performance of ACTs.