Artemisinin Partial Resistance in Ugandan Children With Complicated Malaria

Abstract

This study assesses artemisinin partial resistance, Pfkelch13 variations, and malaria recrudescence in Ugandan children with complicated malaria.

Intravenous artesunate, a semisynthetic derivative of artemisinin, is the World Health Organization (WHO)–recommended treatment for malaria requiring parenteral treatment. Malaria caused 608 000 deaths in 2022, mostly due to Plasmodium falciparum.¹ Artemisinin partial resistance due to Pfkelch13 variations has been documented in East Africa in uncomplicated malaria^2,3 but not in complicated malaria. We assessed artemisinin partial resistance, Pfkelch13 variations, and malaria recrudescence in Ugandan children with complicated malaria.

Methods

We conducted a prospective study of children aged 6 months to 12 years with complicated malaria (febrile, microscopy-confirmed P falciparum parasitemia with evidence of severe disease that required hospitalization) (Table 1) treated with parenteral artesunate followed by oral artemether/lumefantrine in Jinja, Uganda, from 2021 to 2022. Children were enrolled after written informed consent from parents. Presence of Pfkelch13 A675V, C469Y, and R5661H variations was evaluated and outcomes were analyzed for each variation separately. Study outcomes included parasite clearance half-life (estimated time for parasitemia to decrease by 50%), artemisinin partial resistance (half-life for parasite clearance [t_1/2] >5 hours⁴), early treatment failure (persistence of P falciparum parasitemia ≥72 hours after initial treatment), and polymerase chain reaction (PCR)–adjusted recrudescence (repeated clinical malaria [febrile with microscopy-positive P falciparum parasitemia within 28 days of treatment] or asymptomatic P falciparum parasitemia on day 28 after treatment, with 1 or more identical P falciparum genotypes during first and second episodes).⁵ P falciparum genotypes for artemisinin partial resistance and recrudescence were determined by PCR amplification of Pfkelch13 variations and the merozoite surface protein 2 (PfMSP-2) gene, respectively. Blood samples were obtained according to WHO guidelines for parasite clearance evaluation.⁵ Details of enrollment criteria, treatment, microscopy, and genotyping are provided in the eAppendix in Supplement 1. For statistical analysis (Stata SE version 17; StataCorp), continuous and categorical variables were compared using 2-sided t test and Fisher exact probability test with Woolf 95% CIs, respectively, with P < .05 considered significant. The study was approved by the Makerere University School of Medicine Research and Ethics Committee and Uganda National Council for Science and Technology.

Table 1. Clinical Features of Malaria Complications in Study Participants^a.

Clinical feature	No. (%) (N = 100)
Hematologic
Severe malarial anemia (Hb <5 g/dL, parasitemia >10 000/μL)	9
Anemia (Hb 5-6 g/dL), admitted for potential transfusion	13
Neurologic
Cerebral malaria	4
Multiple convulsions (>2 per 24 h)	8
Prostration	1
Kidney
Serum creatinine >3 mg/dL	1
Acute kidney injuryb	42 (58) (n = 73)
Blackwater feverc	10
Other clinical findings
Hyperpyrexia (axillary temperature >39.5 °C)	19
Systolic hypotension (SBP <70 mm Hg)	1
Jaundiced	6
Unable to take oral food or medications	26
Persistent parasitemia and fever despite prior antimalarial drugs	9
Laboratory findings
Hyperparasitemiae	22

Abbreviations: Hb, hemoglobin; SBP, systolic blood pressure.

^a For tests not conducted in the full study cohort, the total number tested is listed. Some children had multiple complications of malaria.

^b Kidney Disease Improving Global Outcomes (KDIGO) criteria.

^c Tea-colored urine.

^d Jaundice at clinical examination.

^e Parasite density greater than 100 000/μL.

Results

Of 110 enrolled children with complicated malaria, 10 were excluded (withdrawn by parents, 8; incomplete testing, 1; died before completing study, 1). Of the 100 participants in the final analysis, 47 were female. The mean (SD) age was 3.72 (2.1) years; 41 participants met current WHO severe malaria criteria,⁶ with the remainder admitted for other severe complications of malaria that required hospital admission (Table 1).

Artemisinin partial resistance was seen in 11 study participants. Eight participants had the A675V variation and 2 the C4692Y variation; none had the R5661H variation. The A675V variation was associated with longer time to parasite clearance (mean [SD] t_1/2 for A675V, 4.9 [2.3] hours; for wild type, 3.2 [1.5] hours; P = .005) and artemisinin partial resistance (proportion with t_1/2 ≥5 hours⁵: A675V, 3 of 8 [37.5%]; wild type, 8 of 90 [8.9%]; odds ratio, 6.2 [95% CI, 1.2-30.6]; P = .04) (Table 2). Both patients with the C469Y variation cleared parasitemia rapidly (mean t_1/2, 1.3 hours). Two children with early treatment failure required prolonged artesunate therapy, 1 with Pfkelch13 A675V (96 hours to clearance) and 1 with wild-type Pfkelch13 (120 hours to clearance) (Table 2).

Table 2. Parasitologic and Clinical Outcomes in Study Participants.

Outcome	Full cohort (N = 100)a	Pfkelch13 wild type (n = 90)	Pfkelch13 A675V (n = 8)
Parasite clearance half-life, mean (SD), hb	3.3 (1.7)	3.2 (1.5)	4.9 (2.3)
Artemisinin partial resistance, No. (%)c	11 (11)	8 (8.9)	3 (37.5)
Early treatment failure, No. (%)d	2 (2)	1 (1.1)	1 (12.5)
Malaria recrudescence, No. (%)e	10 (10.3) (n = 97)	9 (10.1) (n = 89)	1 (12.5)

^a Pfkelch13 wild type (n = 90), Pfkelch13 A675V (n = 8), and Pfkelch13 C469Y (n = 2).

^b Estimated time for parasite density to decrease by 50%.

^c Parasite clearance half-life greater than or equal to 5 hours.

^d Persistence of Plasmodium falciparum parasitemia greater than or equal to 72 hours after initial treatment.

^e Polymerase chain reaction–adjusted 28-day recrudescence (clinical malaria within 28 days of treatment or asymptomatic parasitemia on day 28).

Thirteen participants had a repeated clinical malaria episode despite prior documented parasite clearance. We determined the P falciparum genotype in 11 participants. PCR-adjusted 28-day recrudescence was 10.3% (9 clinical recrudescence and 1 day-28 asymptomatic parasitemia recrudescence out of 97 children with PfMSP-2 genotyping). Recrudescence was not associated with carriage of Pfkelch13 variations at enrollment (1 of 8 children [12.5%] with A675V variation vs 9 of 89 children [10.1%] without A675V variation; P > .99).

Discussion

This study found artemisinin partial resistance in Ugandan children with complicated malaria associated with the Pfkelch13 A675V variation and also found suboptimal 28-day efficacy of parenteral artesunate followed by oral artemether/lumefantrine therapy. Limitations include a small sample size and a single location for the study. Given the high morbidity and risk of death in African children with complications of malaria, additional evaluation of artemisinin resistance in children with complicated malaria is needed because confirmation of the presence of artemisinin partial resistance and clinical treatment failure may require revision of guidelines for treatment of this life-threatening condition.

Section Editors: Kristin Walter, MD, and Jody W. Zylke, MD, Deputy Editors; Karen Lasser, MD, MPH, Senior Editor.

Supplement 1.

eAppendix. Supplementary Materials

eReferences.

Supplement 2.

Data Sharing Statement