The spatial heterogeneity of malaria transmission. An entomological investigation in a highly endemic setting of Burkina Faso

Malaria hotspots are often observed at multiple spatial scales, shaped by environmental, entomological, and human factors. The dynamics underlying transmission heterogeneity remains poorly understood, limiting the effectiveness of locally tailored control strategies. This study investigates transmission spatial patterns in an ITNcovered Burkina Faso village, exploiting entomological predictors of exposure risk in relation to environmental factors. Pyrethrum spray collections were conducted in 59 houses across the north-west, east, and south areas of Goden village. Anopheles mosquitoes were analysed for species identification, human blood index (HBI), sporozoite rate (SR), and infected human blood meal rate (IHBM). Entomological indices and mosquito abundance were spatially interpolated and then included in GAMLSS models to assess the effects of ecological variables. Anopheles coluzzii was the dominant vector, representing 79% of An. gambiae (s.l.) collected (n = 1492). Blood-meal analysis indicated low anthropophily (HBI = 45%, n = 687), yet SR was high (10%, n = 930), likely sustained by elevated parasite circulation among residents. In fact, the IHBM revealed that 43% of human blood meals contained erythrocytic parasite stages. Statistics highlighted a spatial effect on human-vector contacts and proportionally higher values of HBI, SR, and IHBM clustering in the north-west area. This suggests the presence of a hotspot where inhabitants were more exposed to infectious bites, and vectors had greater chances of acquiring Plasmodium spp. Notably, infective mosquitoes had 1.8-fold higher anthropophily than non-infective ones. Although further investigations are needed, this study unveiled a possible mechanism sustaining local hotspots by linking uneven biting exposure of human reservoir and increased anthropophily of infective mosquitoes.