  Malaria transmission in Madagascar is highly heterogeneous, exhibiting
spatial, seasonal and long-term trends. Previous efforts to map malaria risk in
Madagascar used prevalence data from Malaria Indicator Surveys. These
cross-sectional surveys, conducted during the high transmission season most
recently in 2013 and 2016, provide nationally representative prevalence data
but cover relatively short time frames. Conversely, monthly case data are
collected at health facilities but suffer from biases, including incomplete
reporting.
  We combined survey and case data to make monthly maps of prevalence between
2013 and 2016. Health facility catchments were estimated and incidence
surfaces, environmental and socioeconomic covariates, and survey data informed
a Bayesian prevalence model. Prevalence estimates were consistently high in the
coastal regions and low in the highlands. Prevalence was lowest in 2014 and
peaked in 2015, highlighting the importance of estimates between survey years.
Seasonality was widely observed. Similar multi-metric approaches may be
applicable across sub-Saharan Africa.
