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. 2025 Jul 14;15(1):25376.
doi: 10.1038/s41598-025-10500-5.

Tracking Plasmodium falciparum antimalarial resistance markers during a malaria pre-elimination period in the Pacific coast of South America

Isaac Ñacata  1 , Angela M Early  2 , Janeth Boboy  3 , Daniel E Neafsey  2   4 , Fabián E Sáenz  5
Affiliations

Tracking Plasmodium falciparum antimalarial resistance markers during a malaria pre-elimination period in the Pacific coast of South America

Isaac Ñacata et al. Sci Rep. .

Abstract

Antimalarial resistance in Plasmodium falciparum is a public health problem in the fight against malaria in Ecuador. Characterizing the molecular epidemiology of drug resistance genes helps to understand the emergence and spread of resistant parasites. In this study, the effects of drug pressure and human migration on antimalarial resistance in P. falciparum were evaluated. Sixty-seven samples from northwestern Ecuador from the 2019-2021 period were analyzed. SNPs in Pfcrt, Pfdhps, Pfdhfr, Pfmdr-1, Pfk13 and Pfaat1 were identified by Sanger sequencing and whole-genome sequencing. A comparison of the frequencies of the haplotypes was made with data from the 2013-2015 period. Also, nucleotide and haplotype diversity were calculated. The frequencies of the mutant haplotypes, CVMET in Pfcrt and CICNI in Pfdhfr increased and became dominant (100% of infections) in Esmeraldas. NEDFSDFY in Pfmdr-1 was detected for the first time, while two wild-type haplotypes, SAKAA in Pfdhps and MYRIC in Pfk13, remained in 100% of samples. Interestingly, the A16V mutation in Pfdhfr that gives resistance to proguanil is reported in Ecuador for the first time. In conclusion, parasites resistant to chloroquine (Pfcrt) and pyrimethamine (Pfdhfr) increased in recent years, while parasites sensitive to sulfadoxine (Pfdhps) and artemisinin (Pfk13) prevail in Ecuador. These results suggest that the current first-line treatment (artemether-lumefantrine + primaquine) is still useful against P. falciparum.

Keywords: Plasmodium falciparum; Antimalarial; Human migration; Resistance; Selective pressure.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests. Ethics approval and consent to participate: All methods were performed in accordance with guidelines and regulations and in accordance with the declaration of Helsinki. The study was approved by the Research Ethics Committee on Human Beings of Pontificia Universidad Católica del Ecuador registered in the document CEISH-571-2018 and by the Ministry of Public Health (MPH) of Ecuador registered in the document MSP-DIS-2019-044-O.

Figures

Fig. 1
Fig. 1
Origin of studied isolates. Samples collected from patients in northwest Ecuador: Esmeraldas (n = 27), San Lorenzo (n = 5), Tobar Donoso (n = 18) and Colombia (n = 17). Map created using QGIS software (QGIS 3.34 Prizren) (https://www.qgis.org) and edited with Adobe Illustrator version 27 (https://www.adobe.org).
Fig. 2
Fig. 2
Geographic distribution of frequencies of drug resistance haplotypes in the 2019–2021 period. (a) Haplotypes of PfCRT (72–76), (b) Haplotypes of PfDHPS (436, 437, 549, 581 and 613), (c) Haplotypes of PfDHFR (50, 51, 59, 108 and 164), (d) Haplotypes of PfMDR-1 (codons 86, 130, 144, 184, 1034, 1042, 1226 and 1246), (e) Haplotypes of PfK13 (codons 476, 493, 539, 543 and 580).
Fig. 3
Fig. 3
Comparative frequencies of drug resistance haplotypes in Northwest Ecuador between the 2013–2015 and 2019–2022 periods. (a) Haplotypes of PfCRT (72–76), (b) Haplotypes of PfDHPS (436, 437, 549, 581 and 613), (c) Haplotypes of PfDHFR (50, 51, 59, 108 and 164), (d) Haplotypes of PfMDR-1 (codons 86, 130, 144, 184, 1034, 1042, 1226 and 1246), (e) Haplotypes of PfK13 (codons 476, 493, 539, 543 and 580).
Fig. 4
Fig. 4
Antimalarial treatments against P. falciparum in Ecuador. Timeline of antimalarial treatments since 1950 according to the Ministry of Public Health of Ecuador. Chloroquine (CQ), primaquine (PQ), sulfadoxine-pyrimethamine (SP), artemether-lumefantrine (AL), artesunate (AS), quinine (QN) and clindamycin (CM). Source: Aguilar et al..
Fig. 5
Fig. 5
Cross-border and intra-border routes of entry of P. falciparum in northwestern Ecuador. Possible routes of the human migration used for the passage of P. falciparum in the south coast of Colombia and the north coast of Ecuador. Elaborated according to the information collected from oral reports. Map created using QGIS software (QGIS 3.34 Prizren) (https://www.qgis.org) and edited with Adobe Illustrator version 27 (https://www.adobe.org).
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References

    1. PAHO. Epidemiological Update: Malaria in the Americas in the Context of the COVID-19 Pandemic. Pan American Health Organization (2020).
    1. WHO. World Malaria Report. World Health Organizationhttps://www.who.int/malaria/media/world-malaria-report-2019/es/ (2019).
    1. World Health Organization. World Malaria Report 2022. https://www.who.int/teams/global-malaria-programme (2023).
    1. MSP. Malaria: Gacetas Vectoriales. Ministerio de Salud Pública del Ecuadorhttps://www.salud.gob.ec/gacetas-vectoriales/#search (2022).
    1. PAHO. Malaria Situation Report in the Americas: 2017. Pan American Health Organization (2017).

MeSH terms