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Background  Studies in Southeast Asia reported a strong relationship between polymorphisms at the propeller domain of the Kelch 13 (K13) protein encoded by the  Plasmodium  falciparum  k13  (pfk13)  gene and delayed parasite clearance after artemisinin treatment. In Africa,  P. falciparum  remains susceptible and combination therapy regimens which include an artemisinin component display good efficacy. Using quantitative real-time PCR (qPCR), sub-microscopic persistence of  P. falciparum  has previously been reported in one-third of children treated with artemisinin combination therapy (ACT) in western Kenya. In this study, further investigation was made to evaluate whether these sub-microscopic residual parasites also harbour mutations at the propeller region of  pfk13  and whether the mutations, if any, affect treatment outcome.    Methods  The  pfk13  propeller domain was genotyped in DNA samples obtained in 2009 from Kenyan children treated with artemether–lumefantrine (AL) and dihydroartemisinin–piperaquine (DP). Paired samples at pre-treatment (day 0) and day of treatment failure (day 28 or 42) for 32 patients with documented recurrent parasitaemia were available for genotyping. Additional day 3 DNA samples were available for 10 patients.    Results  No mutation associated with artemisinin resistance in Southeast Asia was observed. Only one DP-treated patient harboured a non-synonymous mutation at codon 578 (A578S) of  pfk13 - propeller  gene in the day 0 sample, but this allele was replaced by the wild-type (A578) form on day 3 and on the day of recurrent parasitaemia. The mutation at amino acid codon 578 showed no association with any phenotype. Polymorphisms in  pfk13  were not responsible for parasite persistence and gametocyte carriage in the children treated with ACT.    Conclusion  This study contributes to the ongoing surveillance of suspected artemisinin resistance parasites in Africa by providing baseline prevalence of  k13 -propeller mutations in western Kenya with samples collected from a longitudinal study.   Clinical Trials Registration  NCT00868465.

Lack of K13 mutations in Plasmodium falciparum persisting after artemisinin combination therapy treatment of Kenyan children