Trends in Malaria Epidemiological Factors Following the Implementation of Current Control Strategies in Dangassa, Mali

Background: Over the past decade, three strategies have reduced severe malaria cases and deaths in endemic regions of Africa, Asia, and the Americas, specifically: 1] artemisinin-based combination therapies (ACTs), 2] insecticide-treated bed nets (ITNs) , and 3] intermittent preventive treatment with sulfadoxine-pyrimethamine in pregnancy (IPTp. The rationale for this study was to examine communities in Dangassa, Mali where in 2015 two additional control strategies were implemented: ITN universal coverage and Seasonal Malaria Chemoprevention (SMC) among children less than five years. Methods: This was a prospective study based on a rolling longitudinal cohort of 1,401 subjects participating in biannual smear surveys for the prevalence of asymptomatic P. falciparum infection and continuous surveillance for the incidence of human disease (uncomplicated malaria). Entomologic collections were performed to examine the intensity of transmission based on pyrethroid spray catches, human landing catches, and enzyme-linked immunosorbent assay (ELISA) testing for circumsporozoite antigen. Results: A total of 1,401 participants of all ages were enrolled in the study in 2012 after random sampling of households from the community census list. Prevalence of infection was extremely high in Dangassa varying from 9.5% to 62.8% at the start of the rainy season and from 15.1% to 66.7% at the end of the rainy season. Likewise, the number of vectors per house, biting rates, sporozoïtes rates and entomologic inoculation rates (EIR) were substantially greater in Dangassa. Discussion: The findings for this study are consistent with the progressive implementation of effective malaria control strategies in Dangassa. At baseline (2012-2014), prevalence of P. falciparum was above 60% followed by a significant year-to-year decease starting in 2015. Incidence of uncomplicated infected was greater among children < five years while asymptomatic infection was more frequent among the five to fourteen years old. A significant decrease in entomological inoculation rate was also observed from 2015 to 2020. Likewise, vectors’ density, sporozoïtes rates, and entomologic inoculation rates decrease substantially during the study period. Conclusion: Efficient Implementation of two main malaria prevention strategies in Dangassa substantially contribute to a reduction of both asymptomatic and symptomatic malaria in Dangassa from 2015 to 2020