Slow Clearance of Plasmodium falciparum in Severe Pediatric Malaria, Uganda, 2011–2013

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Michael Hawkes, Andrea L. Conroy, Robert O. Opoka, Sophie Namasopo, Kathleen Zhong, W. Conrad Liles, Chandy C. John, and Kevin C. Kain

Author affiliations: University of Alberta, Edmonton, Alberta, Canada (M. Hawkes); University of Toronto, Toronto, Ontario, Canada (M. Hawkes, A.L. Conroy, K.C. Kain); Mulago Hospital, Kampala, Uganda (R.O. Opoka); Makerere University, Kampala (R. Opoka); Jinja Regional Referral Hospital, Jinja, Uganda (S. Namasopo);University Health Network–Toronto General Hospital, Toronto (K. Zhong, K.C. Kain); University of Washington, Seattle, Washington, USA (W.C. Liles); University of Minnesota, St. Paul, Minnesota, USA (C.C. John); Sandra Rotman Centre for Global Health, Toronto (K.C. Kain)

Abstract

Plasmodium falciparum resistance to artemisinin derivatives is emerging in Asia. We examined molecular markers of resistance in 78 children in Uganda who had severe malaria and were treated with intravenous artesunate. We observed in the K13-propeller domain, A578S, a low-frequency (3/78), nonsynonymous, single-nucleotide polymorphism associated with prolonged parasite clearance.

Resistance of Plasmodium falciparum parasites to artemisinin derivatives threatens the current first-line treatment for severe malaria. Artemisinin resistance was first reported in 2009 in Pailin, western Cambodia (1), and has since become prevalent in the greater Mekong Delta, Vietnam, where standard 3-day courses of artemisinin combination therapies for uncomplicated P. falciparum malaria are now failing (2–4).

Among several putative genetic determinants of parasite resistance to artesunate (3,5), polymorphisms in the propeller domain of a kelch gene on chromosome 13 (PF3D7_1343700; K13) are now recognized as the major determinant of artemisinin resistance observed in P. falciparum isolates from patients in Southeast Asia (3,4,6,7). Various single amino acid substitutions in the K13 protein are associated with a mean increase of 116% in the parasite clearance half-life (t1/2) (4). The mechanism of resistance has been illuminated by a recent study of the P. falciparum transcriptomes from >1,000 acute malaria episodes (6). Slow-clearing parasites exhibited increased expression of unfolded protein response pathways (e.g., chaperone complexes); these pathways may mitigate protein damage caused by artemisinin. Slow-clearing parasites also exhibited decreased expression of proteins involved in DNA replication and decelerated development at the young ring stage. Haplotype analysis suggests that K13 mutations emerged independently in multiple geographic locations in Southeast Asia, causing concerns about the ability to contain resistant parasites (7).

With the widespread use of artemisinin treatment, resulting in continued pressure for natural selection of the most resistant parasites, resistance may emerge in regions beyond Asia, including Africa. The possible increase of parasite resistance to treatment highlights an urgent need to map K13 mutations throughout the malaria-endemic world (7). Consequently, recent molecular epidemiologic analyses of K13 in Senegal (8) and Uganda (9) and in a large collection of >1,100 infections from sub-Saharan Africa (10) have been undertaken, revealing the absence of nonsynonymous single-nucleotide polymorphisms (SNPs) associated with artemisinin resistance in Southeast Asia. Other distinct nonsynonymous SNPs have been discovered in parasites of African origin (9,10), but association of these mutations with a resistance phenotype has not been shown.

Dr. Hawkes is a clinician–scientist (pediatric infectious diseases) at the University of Alberta, Edmonton, Alberta, Canada. His current research includes translational and clinical studies in global pediatric infections (i.e., malaria and pneumonia).

Acknowledgment

Trial operational costs were provided by the Sandra Rotman Centre for Global Health. This work was also supported by donations from Kim Kertland, the Tesari Foundation, the Canadian Institutes of Health Research MOP-244701 and 13721 (K.C.K.), the Canada Research Chair in Molecular Parasitology (K.C.K.), the Canada Research Chair in Infectious Diseases and Inflammation (W.C.L.), the Canadian Institutes of Health Research Clinician–Scientist Training Award (M.H.), and a postdoctoral research award (A.L.C.).

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Table

Table. Characteristics of children infected with severe Plasmodium falciparum malaria parasites harboring the Kelch 13 A578S polymorphism compared with children infected with wild-type parasites, Uganda

Suggested citation for this article: Hawkes M, Conroy AL, Opoka RO, Namasopo S, Zhong K, Liles WC, et al. Slow clearance of Plasmodium falciparum in severe pediatric malaria, Uganda, 2011–2013. Emerg Infect Dis. 2015 Jul [date cited]. http://dx.doi.org/10.3201/eid2107.150213

DOI: 10.3201/eid2107.150213