Assessing leishmaniasis risk in irrigated lands in Central Tunisia using visible-spectrum remote sensing data

The expansion of irrigation in central Tunisia has reshaped landscapes, creating ecological conditions favourable to Phlebotomus sand flies and Leishmania transmission, thereby increasing leishmaniasis risk. To assess these dynamics, a geospatial classification and risk-indexing framework was developed that integrates remote sensing, supervised machine learning, and ecological reasoning on vector habitats. The analysis covered three Central Tunisian sites and their narrower environments - Gafsa, Kairouan, and Sidi Bouzid - from 1984 to 2020. Habitat clustering revealed marked spatial and temporal variability in land-cover composition. Low-risk habitats remained dominant, while irrigated high-suitability areas expanded progressively, particularly after the mid-1990s. Semi-natural habitats fluctuated, and very low-risk areas remained minimal. Ecotone analysis showed strong variability in transitional habitat edges, with peaks corresponding to increases in area-averaged risk indices. Territorial risk indices increased over time in all sites, reaching 0.470 in Gafsa (2012), 0.619 in Kairouan, and 0.507 in Sidi Bouzid (2020). These results indicate that irrigation-driven landscape changes enhance human - vector contact and transmission potential, underscoring the need to integrate irrigation practices into targeted, evidence-based vector management strategies.