Assessment of molecular markers of anti-malarial drug resistance among children participating in a therapeutic efficacy study in western Kenya

• Type of Material: Article
• Authors: Winnie Chebore, Kenya Medical Research Institute; Zhiyong Zhou, Centers for Disease Control and Prevention; Nelli Westercamp, Centers for Disease Control and Prevention; Kephas Otieno, Kenya Medical Research Institute; Ya Ping Shi, Centers for Disease Control and Prevention; Sheila B. Sergent, Centers for Disease Control and Prevention; Kelsey Anne Rondini, Emory University; Samaly Souza Svigel, Centers for Disease Control and Prevention; Benard Guyah, Maseno University; Venkatachalam Udhayakumar, Centers for Disease Control and Prevention; Eric S. Halsey, Centers for Disease Control and Prevention; Aaron M. Samuels, Centers for Disease Control and Prevention; Simon Kariuki, Kenya Medical Research Institute
• Language: English
• Date: 2020-08-14
• Publisher: BioMed Central
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2020
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1186/s12936-020-03358-7
• Title of Journal or Parent Work: Malaria Journal
• Volume: 19
• Grant/Funding Information: Molecular marker testing was funded as part of the PMI Antimalarial Resistance Monitoring in Africa (PARMA) network.; The study was funded by the U.S. President’s Malaria Initiative and the Centers for Disease Control and Prevention.
• Keywords: Pfmdr1; Plasmodium falciparum; Pfk13; Pfcrt; Pfpm2; Anti-malarial drug resistance
• Research Categories: Health Sciences, Epidemiology; Health Sciences, Public Health; Biology, Parasitology

Abstract

Background Anti-malarial drug resistance remains a major threat to global malaria control efforts. In Africa, Plasmodium falciparum remains susceptible to artemisinin-based combination therapy (ACT), but the emergence of resistant parasites in multiple countries in Southeast Asia and concerns over emergence and/or spread of resistant parasites in Africa warrants continuous monitoring. The World Health Organization recommends that surveillance for molecular markers of resistance be included within therapeutic efficacy studies (TES). The current study assessed molecular markers associated with resistance to Artemether−lumefantrine (AL) and Dihydroartemisinin−piperaquine (DP) from samples collected from children aged 6–59 months enrolled in a TES conducted in Siaya County, western Kenya from 2016 to 2017. Methods Three hundred and twenty-three samples collected pre-treatment (day-0) and 110 samples collected at the day of recurrent parasitaemia (up to day 42) were tested for the presence of drug resistance markers in the Pfk13 propeller domain, and the Pfmdr1 and Pfcrt genes by Sanger sequencing. Additionally, the Pfpm2 gene copy number was assessed by real-time polymerase chain reaction. Results No mutations previously associated with artemisinin resistance were detected in the Pfk13 propeller region. However, other non-synonymous mutations in the Pfk13 propeller region were detected. The most common mutation found on day-0 and at day of recurrence in the Pfmdr1 multidrug resistance marker was at codon 184F. Very few mutations were found in the Pfcrt marker (< 5%). Within the DP arm, all recrudescent cases (8 sample pairs) that were tested for Pfpm2 gene copy number had a single gene copy. None of the associations between observed mutations and treatment outcomes were statistically significant. Conclusion The results indicate absence of Pfk13 mutations associated with parasite resistance to artemisinin in this area and a very high proportion of wild-type parasites for Pfcrt. Although the frequency of Pfmdr1 184F mutations was high in these samples, the association with treatment failure did not reach statistical significance. As the spread of artemisinin-resistant parasites remains a possibility, continued monitoring for molecular markers of ACT resistance is needed to complement clinical data to inform treatment policy in Kenya and other malaria-endemic regions.