Plasmodium falciparum gametocyte burden in a Tanzanian heterogeneous transmission setting
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Date
2025-02-21
Journal Title
Journal ISSN
Volume Title
Publisher
Springer Nature
Abstract
Background Malaria transmission depends on the presence of gametocytes in the peripheral blood of infected
human hosts. Understanding malaria infectious reservoirs enables transmission-blocking interventions to target
the most important hosts for the disease. This study characterized the distribution of gametocyte carriage as a base-
line for the clinical evaluation of a Pfs25-based transmission-blocking vaccine candidate in Bagamoyo, Tanzania.
Methods A malaria survey was conducted in five locations from May to August 2022. A total of 467 partici-
pants—192 children (5–12 years), 65 adolescents (13–17 years) and 210 adults (18–45 years)—were enrolled. Malaria
was detected using three methods: rapid diagnostic tests, light microscopy and quantitative polymerase chain reac-
tion. The geometric mean of the gametocyte density, and weighted arithmetic mean of the gametocytes sex ratio
were estimated.
Results Overall, 23.5% (110/467) of the participants tested positive for malaria parasites, with the majority of posi-
tives (> 92%) being Plasmodium falciparum. The overall gametocytaemia was 5.6%, with a percent positivity of 6.8%
(13/192), 6.2% (4/65) and 4.3% (9/210), in children, adolescents, and adults, respectively. The geometric mean gameto-
cyte density (gametocytes/μL) was greater in adults (124.6) than in children (71.7) and adolescents (50.5). Regression
analysis revealed that gametocytes were more likely to be present among male participants than among female par-
ticipants [ORa: 2.79 (95% CI: 1.19 – 6.59) p = 0.019]. The gametocyte sex ratio in children and adult gametocyte carriers
was similar but greater than that in adolescents.
Conclusion The observed gametocyte densities and distribution across age groups suggest the need for malaria
transmission-blocking interventions to target all populations in heterogeneous transmission settings. The implication
of targeting only children may leave residual malaria transmission and reinfection from the left-out groups
Sustainable Development Goals
SDG - 3: Good Health and Well-being
SDG - 9: Industry, Innovation and Infrastructure
SDG -17: Partnerships for the Goals
Keywords
Malaria transmission, Transmission-blocking vaccines, Plasmodium falciparum, Gametocytes, Tanzania