Not all MDAs should be created equal – determinants of MDA impact and designing MDAs towards malaria elimination

Abstract

11Malaria remains at the forefront of scientific research and global political and funding agendas. 12 Previous malaria models of mass-interventions have consistently oversimplified how mass 13 interventions are implemented. We present an individual based, spatially explicit model of malaria 14 transmission that includes all the programmatic implementation details of mass drug 15 administration (MDA) campaigns. We uncover how the impact of MDA campaigns is determined 16 by the interaction between implementation logistics, patterns of human mobility and how 17 transmission risk is distributed over space. This translates into a higher likelihood of malaria 18 elimination for areas with true prevalence under 3% with a faster implementation, in highly mobile 19populations. If populations are more static, deploying less interventions teams would be cost 20 optimal and predicted to be as impactful. We conclude that mass drug interventions can be an 21 invaluable tool towards malaria elimination in the right context, specifically when paired with 22 effective vector control. 23 24 25 timelines (3). Alignment of global funding bodies' goodwill with sound national malaria control 30programmes is crucial for elimination timelines to be met (4,5), but spreading artemisinin 31 resistance creates a race against time before malaria becomes untreatable with currently available 32 drugs (6,7). 33Vector control and early diagnosis followed by effective antimalarial treatment have been the 34 mainstay of malaria control programmes, but modelling based projections indicate these 35 approaches alone are unlikely to achieve falciparum malaria elimination before failing drug 36 efficacy becomes an issue. Elimination will require more intensive measures to clear the infectious 37 reservoir in asymptomatic populations, especially in the GMS where existing vector bionomics 38 make vector control particularly challenging. The most abundant vector species in the GMS are 39 exophilic (mainly bite outdoors), do not preferentially bite humans, and can bite quite early in the 40 evening (8), rendering typical vector control measures such as insecticide treated nets (ITNs) and 41 indoor residual spraying (IRS) sub-optimal.42 Population wide interventions, including mass drug administration (MDA), are under 43 consideration to clear the infectious reservoir in asymptomatic populations and potentially hasten44progress toward elimination (9,10). The proportion of the target population receiving these 45 interventions ("coverage") is believed to determine their success (4,(11)(12)(13). This success can be 46 considered at two spatial levels: global or local. Whilst malaria elimination campaigns have been carried out successfully in some countries or locally in specific regions (14-16), reintroductions 48 of malaria from surrounding endemic areas are a constant threat (17,18). The significance of 49 mobile populations as a source of malaria transmission in the GMS has been emphasized in recent 50 years (19)(20)(21)(22)(23)(24). Prompt treatment of n...