Treatment Failure and Post-Artesunate Delayed Haemolysis in a Returned Traveller From Uganda With Partially Drug-Resistant Severe Plasmodium falciparum Malaria

A man aged in his 40s, recently returned from Uganda, was hospitalised with Plasmodium falciparum malaria, with hyperparasitaemia of ~1.5 × 10⁶ parasites/μL (26%). He received intravenous artesunate followed by artemether-lumefantrine. However, parasite clearance was delayed, and despite a negative blood film following treatment, the patient was readmitted 3 weeks later with recurrent parasitaemia. Further testing for drug-resistant phenotypes and genotypes demonstrated reduced susceptibility to lumefantrine, an A675V mutation in the pfk13 gene and increased ring-stage survival, consistent with partial artemisinin resistance. The case highlights the high risk of P. falciparum treatment failure in patients with hyperparasitaemia and partial drug resistance.