Ecological and social determinants of dengue and chikungunya along an altitudinal gradient in Central Nepal

Climate change is increasingly influencing the epidemiology of vector-borne diseases (VBDs) in the Hindu Kush Himalayan (HKH) region, with significant implications for public health. This PhD research examines the ecological and social determinants of dengue and chikungunya along an altitudinal gradient in Central Nepal, addressing critical evidence gaps related to climate change, disease distribution, and community responses across different elevations. A concurrent cross-sectional mixed-methods approach was conducted between September and October 2018, integrating quantitative household surveys (n = 660) and qualitative data from 27 in-depth interviews and 12 focus group discussions. The study was guided by four research objectives: (RO1) assessment of climate trends and community perceptions, (RO2) spatiotemporal distribution of dengue and chikungunya, (RO3) community knowledge, attitudes, and practices (KAP) related to dengue, and (RO4) challenges in vector control implementation. Results show a strong agreement between perceived and observed climate trends, particularly increasing summer temperatures (p < 0.001), while perceptions of rainfall variability differed significantly by altitude (p < 0.001). Communities across all elevation zones reported increasing climate-related extreme events, including floods, droughts, and landslides, with perceived impacts on agriculture, water resources, biodiversity, and human health. The systematic review of 66 studies revealed substantial geographic expansion of dengue and chikungunya across the HKH region, with Nepal accounting for the highest proportion of reported dengue cases (56.83%), peaking during the post-monsoon (September-November). Household survey findings indicate low dengue awareness and limited preventive practices, despite generally positive attitudes. Education and income were positively associated with knowledge (p < 0.01). Qualitative findings highlighted growing concern among stakeholders regarding future dengue risk due to climate change and human mobility. Vector control efforts were found largely reactive, outbreak-oriented, and constrained by limited resources, weak coordination, and insufficient community engagement. This thesis demonstrates that climate change is reshaping dengue risks along Nepal’s altitudinal gradient, while highlighting that chikungunya is an emerging regional threat in the HKH. The findings underscore the necessity for climate-informed, region-specific public health policies, strengthened surveillance, and targeted awareness programs to improve preparedness for climate-sensitive health threats in Nepal and the HKH region.