Sero-epidemiological evaluation of malaria transmission in The Gambia before and after mass drug administration

BackgroundAs The Gambia aims to achieve elimination by 2030, serological assays are a useful surveillance tool to monitor trends in malaria incidence and evaluate community-based interventions. MethodsWithin a mass drug administration (MDA) study in The Gambia, where reduced malaria infection and clinical disease were observed after the intervention, a serological sub-study was conducted in four study villages. Spatio-temporal variation in transmission was measured with a panel of recombinant Pf antigens on a multiplexed bead-based assay. Village-level antibody levels were quantified as under-15 sero-prevalence, sero-conversion rates, and age-adjusted antibody acquisition rates. Antibody levels prior to MDA were assessed for association with persistent malaria infection after community chemoprophylaxis. ResultsSeasonal changes in antibodies to Etramp5.Ag1 were observed in children under 15 in two transmission settings - the West Coast and Upper River Regions (4{middle dot}32% and 31{middle dot}30% Pf prevalence, respectively). At the end of the malaria season, short-lived antibody responses to Etramp5.Ag1, GEXP18, HSP40.Ag1, EBA175 RIII-V, and Rh2.2030 were lower amongst 1-15 year olds in the West Coast compared to the Upper River, reflecting known differences in transmission. Prior to MDA, individuals in the top 50th percentile of antibody levels had two-fold higher odds of clinical malaria during the transmission season, consistent with previous findings where individuals infected pre-MDA had 2-fold higher odds of re-infection post-MDA. ConclusionSerological markers can serve dual functions as indicators of malaria exposure and incidence. Further studies, particularly cluster randomised trials, can help establish standardised serological protocols to measure transmission across endemic settings.