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Background: Plasmodium falciparum resistance to anti-malarials is a major drawback in effective malaria control and elimination globally. Artemisinin-combination therapy (ACT) is currently the key first-line treatment for uncomplicated falciparum malaria. Plasmodium falciparum genetic signatures at pfmdr-1, pfcrt, and pfubp-1 loci are known to modulate in vivo and in vitro parasite response to ACT. The objective of this study was to assess the distribution of these resistance gene markers in isolates collected from different malaria transmission intensity in Ethiopia and Tanzania. Methods: Plasmodium falciparum clinical isolates were collected from different regions of Ethiopia and Tanzania. Genetic polymorphisms in the genes pfcrt, pfmdr-1 and pfubp-1 were analysed by PCR and sequencing. Frequencies of the different alleles in the three genes were compared within and between regions, and between the two countries. Results: The majority of the isolates from Ethiopia were mutant for the pfcrt 76 and wild-type for pfmdr-1 86. In contrast, the majority of the Tanzanian samples were wild-type for both pfcrt and pfmdr-1 loci. Analysis of a variable linker region in pfmdr-1 showed substantial variation in isolates from Tanzania as compared to Ethiopian isolates that had minimal variation. Direct sequencing of the pfubp-1 region showed that 92.8% (26/28) of the Ethiopian isolates had identical genome sequence with the wild type reference P. falciparum strain 3D7. Of 42 isolates from Tanzania, only 13 (30.9%) had identical genome sequences with 3D7. In the Tanzanian samples, 10 variant haplotypes were identified. Conclusion: The majority of Ethiopian isolates carried the main marker for chloroquine (CQ) resistance, while the majority of the samples from Tanzania carried markers for CQ susceptibility. Polymorphic genes showed substantially more variation in Tanzanian isolates. The low variability in the polymorphic region of pfmdr-1 in Ethiopia may be a consequence of low transmission intensity as compared to high transmission intensity and large variations in Tanzania. [ABSTRACT FROM AUTHOR]

Background: Artemisinin-based combination therapy (ACT) is the first-line anti-malarial treatment of uncomplicated malaria in most malaria endemic countries, including Tanzania. Unfortunately, there have been reports of artemisinin resistance and ACT failure from South East Asia highlighting the need to monitor therapeutic efficacy of ACT in these countries as recommended by World Health Organization. Methods: Open-label single arm studies in mainland Tanzania were conducted in nine sentinel sites in 2011, 2012 and 2015 to assess the efficacy and safety of artemether/lumefantrine (AL) and artesunate/amodiaquine (ASAQ) using 28 days follow-up and dihydroartemisinin/piperaquine (DHAPQ) using 42 days follow-up. Mutations in the propeller domain of the Plasmodium falciparum kelch 13 (k13) gene and amplification of the P. falciparum plasmepsin 2 (pm2) gene, associated with artemisinin and piperaquine (PQ) resistance, were also investigated. Results: Of the 428 patients enrolled, 328 patients provided study endpoint. For AL, the PCR corrected per-protocol analysis showed adequate clinical and parasitological response (ACPR) of 90.3% (n = 28; 95% CI 74.2–98.0) in Kyela 2012, 95.7% (n = 22; 95% CI 78.1–99.0) in Chamwino, 100% in Muheza (n = 29; 95% CI 88.1–100), 100% in Nagaga (n = 39; 95% CI 91.0–100) and Kyela 2015 (n = 60; 95% CI 94.0–100). For ASAQ, PCR corrected ACPR of 98% (n = 49; 95% CI 89.4–99.9) and 100% (n = 25; 95% CI 86.3–100) were observed in 2011 in Ujiji and Kibaha, respectively. For DHAPQ, the ACPR was 100% (n = 71; 95% CI 94.9–100). Of the 235 samples with genetic interpretable results, only 7 (3%) had non-synonymous k13 mutations. None of these are candidate or validated markers of artemisinin resistance and all patients carrying these alleles cleared the parasites on day 3. Of the DHAPQ group, 10% (3/29) of the samples with interpretable results had pm2 multiple copies and none of them was associated with treatment failure. Conclusion: All the tested ACT in mainland Tanzania were highly efficacious and none of validated k13 mutants associated with artemisinin resistance was observed. However, three isolates with multiple copy numbers of pm2 gene associated with PQ resistance among the limited samples tested successfully calls for further investigation. Trial registration Number ACTRN12615000159550. Registered 18th February 2015, https://www.anzctr.org.au/trial/MyTrial.aspx [ABSTRACT FROM AUTHOR]