Sub-national tailoring of seasonal malaria chemoprevention in Mali based on malaria surveillance and rainfall data

Abstract

Background In malaria endemic countries, seasonal malaria chemoprevention (SMC) interventions are performed during the high malaria transmission in accordance with epidemiological surveillance data. In this study we propose a predictive approach for tailoring the timing and number of cycles of SMC in all health districts of Mali based on sub-national epidemiological surveillance and rainfall data. Our primary objective was to select the best of two approaches for predicting the onset of the high transmission season at the operational scale. Our secondary objective was to evaluate the number of malaria cases, hospitalisations and deaths in children under 5 years of age that would be prevented annually and the additional cost that would be incurred using the best approach. Methods For each of the 75 health districts of Mali over the study period (2014–2019), we determined (1) the onset of the rainy season period based on weekly rainfall data; (ii) the onset and duration of the high transmission season using change point analysis of weekly incidence data; and (iii) the lag between the onset of the rainy season and the onset of the high transmission. Two approaches for predicting the onset of the high transmission season in 2019 were evaluated. Results In the study period (2014–2019), the onset of the rainy season ranged from week (W) 17 (W17; April) to W34 (August). The onset of the high transmission season ranged from W25 (June) to W40 (September). The lag between these two events ranged from 5 to 12 weeks. The duration of the high transmission season ranged from 3 to 6 months. The best of the two approaches predicted the onset of the high transmission season in 2019 to be in June in two districts, in July in 46 districts, in August in 21 districts and in September in six districts. Using our proposed approach would prevent 43,819 cases, 1943 hospitalisations and 70 deaths in children under 5 years of age annually for a minimal additional cost. Our analysis shows that the number of cycles of SMC should be changed in 36 health districts. Conclusion Adapting the timing of SMC interventions using our proposed approach could improve the prevention of malaria cases and decrease hospitalisations and deaths. Future studies should be conducted to validate this approach. Graphical Abstract

Impact of seasonal malaria chemoprevention timing on clinical malaria incidence dynamics in the Kedougou region, Senegal

“…Thus, they fully support the decision of Senegalese NMCP to add a fifth round of SMC in the Kedougou region (9). Evidence-based improvement of SMC intervention allocation is also ongoing in several countries, to adapt the start and duration of SMC campaigns to regional malaria transmission patterns (12).…”

“…Previous studies conducted in Sahelian countries have shown that SMC protects children for 28 days and thus requires a strict timing of SMC programs with repeated treatments at monthly intervals to achieve optimal results (2,11). Other studies suggested that the number of rounds should be adapted to the duration of the high transmission season(12) Indeed, the Senegalese NMCP reported that >50% of malaria cases in 2020 occurred after the final round of SMC despite high coverage of SMC (9,13), suggesting that the 4 rounds may not provide adequate cover throughout the entire high-risk season. In addition, resistance to sulfadoxine-pyrimethamine remains a major threat to SMC effectiveness (14).…”

“…Community health workers (CHW) administer monthly SMC to children between 3 months to 5 10 years of age during the high transmission season. All 3 days of treatment are directly observed by CHW with a door-to-door approach (12). SMC is currently conducted in 16 high-burden districts of 5 regions (12).…”

“…All 3 days of treatment are directly observed by CHW with a door-to-door approach (12). SMC is currently conducted in 16 high-burden districts of 5 regions (12). The number of rounds in the campaign is defined by region and depends on the duration of the high transmission season.…”

Malaria prevention in children: an update

“…The new WHO guideline flexibility will allow for more tailored responses between countries and even subnational areas within countries. A recent study of SMC in Mali showed that using rainfall data and weekly incidence data to inform the timing of SMC and the number of cycles at a subnational level could prevent tens of thousands of malaria cases with minimal cost increase [15 ▪▪ ]. A qualitative study in Burkina Faso highlighted the importance of studying SMC feasibility and acceptability before rolling out additional interventions, though, as a fifth cycle of SMC overlapped with farming activities, so timing of distribution required optimization for good uptake [16 ▪ ].…”