A Single Mutation in K13 Predominates in Southern China and Is Associated With Delayed Clearance of Plasmodium falciparum Following Artemisinin Treatment

Abstract

Background: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and poses a threat to malaria control and elimination. Mutations in a P. falciparum gene encoding a kelch protein on chromosome 13 have been associated with delayed parasite clearance following artemisinin treatment elsewhere in the region, but not yet in China.

Methods: Therapeutic efficacy studies of artesunate and dihydroartemisinin-piperaquine were conducted from 2009 to 2012 in the Yunnan Province of China near the border with Myanmar. K13 mutations were genotyped by capillary sequencing of DNA extracted from dried blood spots collected in these clinical trials and in routine surveillance. Associations between K13 mutations and delayed parasite clearance were tested using regression models.

Results: Parasite clearance half-lives were prolonged after artemisinin treatment, with 44% of infections having half-lives >5 hours (n = 109). Fourteen mutations in K13 were observed, with an overall prevalence of 47.7% (n = 329). A single mutation, F446I, predominated, with a prevalence of 36.5%. Infections with F446I were significantly associated with parasitemia on day 3 following artemisinin treatment and with longer clearance half-lives.

Conclusions: Plasmodium falciparum infections in southern China displayed markedly delayed clearance following artemisinin treatment. F446I was the predominant K13 mutation and was associated with delayed parasite clearance.

Keywords: China; Plasmodium falciparum; artemisinin resistance; kelch 13; malaria.

Figure 1.

Locations for sample collection. Therapeutic efficacy study sites in Yunnan Province (green) include Yingjiang, Tengchong, and Menglian counties, shown in red. Hainan Province and Yunnan Province are shown in blue and green, respectively.

Figure 2.

Distribution of parasite clearance half-lives by study site (A) and proportion of study participants with different parasite clearance half-lives (B). Box plots depict interquartile range, with data falling outside this range appearing as open circles.

Figure 3.

Association of K13 mutations with parasite clearance half-lives (A) and prevalence of infections with all K13 propeller mutations (B). Parasite clearance half-lives with K13 mutations (colors) or wild-type (WT) alleles (green).