Current and Future Projection of Scrub Typhus Risk Related to Land Use Change in China

The widespread concern surrounding the enhanced spillover risk of infectious diseases due to dramatic global land use changes has sparked significant discussion. However, the specific implications of these changes on scrub typhus, a vector-borne infectious disease facing increasing incidence and substantial expansion, remain unclear. Here, we constructed a comprehensive landscape fragmentation index (LFI), which reflects the interaction between human activities and natural habitats. Then we utilized a generalized additive model (GAM) to estimate the comprehensive and segmented impacts of LFI on scrub typhus incidence in China, grouping the results by year, land use type and fragmentation level. Additionally, we projected changes in such impacts under four shared socioeconomic pathways (SSPs), including SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. Key results were: (a) The LFI exhibited a nonlinear positive correlation with scrub typhus incidence. Each 0.1 increase in the LFI was associated with a relative risk of 1.20 (95% CI:1.19-1.21) for scrub typhus. Notably, at higher fragmentation levels, scrub typhus incidence tended to decrease. (b) Forest fragmentation had the most significant impact on scrub typhus, followed by cropland fragmentation, whereas construction land fragmentation was negatively associated. (c) The future areas of elevated scrub typhus risk varied among the SSPs, but they were mainly concentrated at the interface between urban expansion and natural habitats. Our results indicate that human interference with the natural ecosystem is a critical factor for the incidence of scrub typhus. These findings are conducive to promoting ecological protection and the prevention and control of scrub typhus.