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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]

Abstract: Background: Malaria is still a major public health problem in the world and sub-Saharan Africa is one of the most affected areas. Efforts to control malaria are highly affected by drug resistance to commonly used antimalarials. The introduction of artemisinin based combination therapy (ACT) as a first line drug seems to be a major step in treatment of uncomplicated malaria, though search for drugs to combine with artemisinins still continues. There have been reports on increased prevalence of the wild type markers Pfcrt 76K and Pfmdr1 86N in some African countries and ideas of using chloroquine (CQ) in intermittent presumptive treatment for adults (IPTa) is coming up. The common combination of artemether and lumefantrine even selects for parasites that are wild type at these positions. This study is comparing prevalence of mutation at these two positions in two East African countries with ACT as their first line drug but following somewhat different drug policies regarding CQ. In Tanzania CQ was stopped in 2001 but in Uganda CQ was retained in combination with sulfadoxine–pyrimethamine (SP) and used in home based management of fever for some time. SP is still used in IPT for pregnant women. Methods: Blood smears and dried blood spots on Whatman filter papers were collected from 100 patients with uncomplicated malaria in Mwanza, Tanzania and 100 patients from Iganga, Uganda. DNA was extracted from all samples using Tris EDTA method. PCR and RFLP were performed and sequencing done on Pfcrt amplification products. Results: The prevalence of K76T mutations at Pfcrt in samples from Mwanza, Tanzania was 40.5% (34/84) and 100% (100/100) in samples from Iganga, Uganda. Prevalence of N86Y mutations in Pfmdr1 was 16.9% (13/77) and 77.7% (63/81) in samples from Mwanza and Iganga, respectively. The re-emergence of CQ sensitive isolates in Mwanza, Tanzania showed the haplotype CVMNK typical for wild type isolates. Conclusions: The prevalence of CQ resistant parasites in Mwanza, Tanzania is low compared to the existing high level of resistant parasites in Iganga, Uganda. This could be an indication that CQ may become useful in the future in Tanzania. This study shows clearly that there is a difference in mutations at these positions in these two countries implementing similar but somewhat different drug policies. In Uganda the drug resistance has reached fixation while in Tanzania the prevalence is going down. [Copyright &y& Elsevier]

High‐throughput Plasmodium genomic data is increasingly useful in assessing prevalence of clinically important mutations and malaria transmission patterns. Understanding parasite diversity is important for identification of specific human or parasite populations that can be targeted by control programmes, and to monitor the spread of mutations associated with drug resistance. An up‐to‐date understanding of regional parasite population dynamics is also critical to monitor the impact of control efforts. However, this data is largely absent from high‐burden nations in Africa, and to date, no such analysis has been conducted for malaria parasites in Tanzania countrywide. To this end, over 1,000 P. falciparum clinical isolates were collected in 2017 from 13 sites in seven administrative regions across Tanzania, and parasites were genotyped at 1,800 variable positions genome‐wide using molecular inversion probes. Population structure was detectable among Tanzanian P. falciparum parasites, approximately separating parasites from the northern and southern districts and identifying genetically admixed populations in the north. Isolates from nearby districts were more likely to be genetically related compared to parasites sampled from more distant districts. Known drug resistance mutations were seen at increased frequency in northern districts (including two infections carrying pfk13‐R561H), and additional variants with undetermined significance for antimalarial resistance also varied by geography. Malaria Indicator Survey (2017) data corresponded with genetic findings, including average region‐level complexity‐of‐infection and malaria prevalence estimates. The parasite populations identified here provide important information on extant spatial patterns of genetic diversity of Tanzanian parasites, to which future surveys of genetic relatedness can be compared. [ABSTRACT FROM AUTHOR]