A prospective longitudinal study on the elimination trend of rural cutaneous leishmaniasis in southeastern Iran: Climate change, population displacement, and agricultural transition from 1991 to 2021

Leishmaniasis is a complex disease. Any change in weather conditions affects the humans' social and agricultural expansion and, consequently, the parasite's life cycle in terms of ecology, biodiversity, social stigma, and exclusion. This population-based prospective longitudinal investigation was conducted between 1991 and 2021 in a well-defined CL (cutaneous leishmaniasis) focus in Bam County, southeastern Iran. A robust health clinic and health surveillance system were responsible for the ongoing systematic documentation, detection, identification, and management of CL cases. The exponential smoothing method via the state space model was used in the univariate time series. The TTR, smooth, and forecast packages were used in R software. Landsat satellite images from 1991, 2001, 2011, and 2021 were employed in the physical development. During this period, the temperature increased while the rainfall and humidity decreased. The findings showed a downward trend in the standardized drought index. Also, the results showed that climate warming and ecological changes profoundly affected the area's agricultural patterns and topographical features. Furthermore, the last three decades witnessed an elimination trend for zoonotic CL (ZCL) and the predominance of anthroponotic CL (ACL). The present findings showed that the critical factors in the predominance of ACL and elimination of ZCL were rising temperature, drought, migration, unplanned urbanization, earthquake, and agrarian reform. The wall-enclosed palm tree gardens excluded the primary ZCL reservoir host. They controlled the disease while providing suitable conditions for the emergence/re-emergence of ACL in the newly established settlements and the unplanned ecozone. Therefore, robust health infrastructures, sustained financial support, and evidence-based research studies are crucial to facilitating the necessary surveillance, monitoring, and evaluation to control and eliminate the disease.