Evaluation of Attractive Targeted Sugar Baits, a new outdoor vector control strategy against malaria: Results from a cluster randomised open-label parallel arm controlled trial in Southwestern Mali

Background: The Attractive Targeted Sugar Bait (ATSB) is a new malaria outdoor vector control tool targeting sugar-feeding behaviours of vector mosquitoes. In Mali, a two-year open-label two-arm cluster randomised controlled trial compared the efficacy and safety of ATSB plus insecticide treated mosquito nets (ITN) versus ITN alone on malaria burden. Methods: 76 clusters were formed, of which 38 were randomly allocated to the intervention. Cohort studies and household surveys were performed to assess clinical malaria incidence (primary outcome) in children aged 5 to 14 years and malaria infection prevalence in individuals aged 6 months or older, respectively. Primary analyses were performed on an intention-to-treat basis. The trial was designed to detect a minimum 30% reduction in the two outcomes over a two-year period with a power of at least 80%. The trial is registered at ClinicalTrial.gov (NCT04149119). Findings: The proportion of sleeping buildings with at least 2 ATSB ranged between 70% and 80%. Coverage of ATSB in good condition was lower (50% or less). Over the two-year trial period, the clinical malaria incidence rate in the control and intervention arm was 0.726 and 0.660 cases per person-year, respectively, with no statistical evidence for an intervention effect (Incidence Rate Ratio (IRR) = 0.90; 95%CI 0.77, 1.05; p = 0.188). Malaria infection prevalence was approximately 37% in both arms (Odds Ratio (OR) = 0.96; 95%CI 0.76, 1.21; p = 0.729). In clusters with coverage of stations in good condition above 80%, there was evidence for a 26% reduction in malaria incidence compared to control clusters after controlling for confounders (adjusted IRR = 0.74; 95%CI 0.61, 0.90; p = 0.002). Interpretation: Overall, the trial did not demonstrate evidence of additional protection against malaria of ATSB compared to using ITN alone. Suboptimal coverage and maintenance of ATSB in good condition in the field may explain the lack of an intervention effect.