Updated mapping of Plasmodium falciparum kelch13 gene polymorphisms in Madagascar, 2024

OBJECTIVES: Artemisinin-resistant Plasmodium falciparum has emerged in several East African countries neighbouring Madagascar. Despite the island's substantial malaria burden, recent data on artemisinin partial resistance are limited, raising concerns about the potential emergence of resistant parasites. This study provides an updated overview of the prevalence and diversity of P. falciparum Kelch13 (pfkelch13) polymorphisms in Madagascar. METHODS: During a nationally representative, cross-sectional survey conducted between January and May 2024, dried blood samples were collected from 4850 febrile patients at 65 health facilities. Pfkelch13 genotyping was performed using a targeted amplicon deep sequencing approach. RESULTS: Of the 1944 P. falciparum-positive samples, 963 (49.5%) pfkelch13 sequences were successfully obtained, and 885 (91.9%) corresponded to the 3D7 wild-type. Non-synonymous and synonymous mutations were detected in 1.8% (17/963) and 6.2% (60/963) of isolates, respectively, whereas one isolate (0.1%) carried double mutations. Of the 18 mutations identified, 5 had not been previously reported. The two most frequent polymorphisms in Madagascar were the synonymous mutations C469C (3.0%, 29/963) and P417P (2.8%, 27/963). None of the WHO-validated artemisinin partial resistance markers were detected. CONCLUSION: This study provides an updated baseline of pfkelch13 polymorphisms in Madagascar, with no evidence of artemisinin partial resistance emergence. Importantly, no parasites harbouring a validated artemisinin resistance marker were detected across the regions sampled, suggesting that resistant parasites have not yet become established. These findings provide a valuable baseline for future genomic surveillance efforts aimed at the early detection of mutations associated with artemisinin partial resistance.