Plasmodium falciparum infectious reservoir in a rural setting in Burkina Faso: a two-year cohort study

BackgroundMalaria caused by Plasmodium falciparum remains a major global health challenge. Although clinical disease results from asexual blood-stage replication, transmission depends on gametocyte carriage. We characterized the seasonal dynamics of the human infectious reservoir in a rural high-transmission setting in Burkina Faso. MethodsWe conducted a 2-year cohort study (2019-2020) including 871 individuals of all ages from four villages in the Nanoro health district. Participants were actively screened for asymptomatic infections three times per year and passively monitored for clinical malaria. P. falciparum infections were detected by light microscopy, targeting parasite DNA and gametocyte marker RNA. ResultsBoth symptomatic and asymptomatic infections showed marked seasonality, peaking in September-October, with 79-83% of clinical cases occurring in the high-transmission season (HTS, July-December). Asymptomatic infections were frequent during the low-transmission season (39.8-46.8%) and increased during the HTS (54.4-62.3%). Age was the strongest predictor of asymptomatic infection and gametocyte carriage: children aged 5-19 years had a 2-fold higher risk of gametocyte carriage, compared with children aged 1-4 years. Anaemia, reticulocyte count, and village of residence were also associated with gametocyte carriage. Infectiousness peaked sightly earlier than infection, and both symptomatic and asymptomatic individuals--predominantly <15 years--contributed substantially to the reservoir. ConclusionIndividuals (5-19 years) sustain a large and persistent infectious reservoir across seasons. Targeted interventions in these age groups are essential to reduce malaria transmission in high, seasonal transmission settings. FundingBelgium Directorate General for Development Cooperation (DGD); Research Foundation Flanders (FWO).