Asymptomatic malaria infections contribute substantially to silent transmission, but the prevalence of artemisinin resistance (ART-R) markers in these carriers remains poorly understood. A community-based cross-sectional study was conducted in Tanzania from December 2022 to July 2023, enrolling 3,489 participants from high-transmission regions of Geita and Kigoma and a low-transmission region of Arusha. Four villages per region were randomly selected, and venous blood samples were tested using rapid diagnostic tests, microscopy, and qPCR, revealing overall positivity rate of 24.4%, 15.8%, and 26.2%, respectively, which indicate a significant proportion of submicroscopic infections. Among the 802 isolates successfully sequenced for pfk13 and pfmdr1, 24 (3.0%) isolates from high-transmission areas carried validated pfk13 partial-resistance markers Y493H (0.2%), R561H (2.0%), and A675V (0.7%), while all low-transmission isolates were wild-type. All isolates retained the pfmdr1 N86 codon, and the NFD haplotype associated with reduced susceptibility to lumefantrine was detected in 48.1% and 48.4% of isolates in high- and low-transmission areas, respectively. Mutations were more frequent in children under five and in females. Artemether-lumefantrine (AL, 64.7%) was the most commonly used antimalarial in high-transmission areas, whereas sulfadoxine-pyrimethamine (SP, 75.9%) predominated in low-transmission areas. Higher AL use correlated with increased pfmdr1 mutation prevalence in high-transmission regions, while NFD detection in low-transmission areas may reflect gene flow from high-transmission settings. These findings demonstrate that asymptomatic carriers are a substantial hidden reservoir of ART-resistant parasites, emphasizing the importance of integrating molecular surveillance and demographic information on asymptomatic infections into malaria control programs to detect emerging resistance and guide targeted interventions in Tanzania.
Mazigo et al. (Tue,) studied this question.