Environmental and Entomological Determinants of Dengue Transmission in Arid and Semi-Arid Rajasthan, India: Implications for Public Health Risk Management

Background: Dengue transmission is increasingly recognized in environments that are traditionally considered less favourable for sustained Aedes mosquito proliferation. Rajasthan contains extensive arid and semi-arid landscapes where seasonal water availability, domestic water storage and climatic variability may create localized ecological conditions favourable for dengue transmission. Objective: The present study examined dengue occurrence in selected arid and semi-arid districts of Rajasthan and evaluated environmental and entomological characteristics relevant to Aedes aegypti persistence in a semi-arid setting. Materials and Methods: Retrospective dengue surveillance data were compiled for six districts of Rajasthan during 2015–2019, comprising arid districts (Jaisalmer, Barmer and Bikaner) and semi-arid districts (Jodhpur, Sri Ganganagar and Hanumangarh). In addition, entomological observations were undertaken in domestic and peri-domestic settings in Jodhpur. Climatic observations and laboratory surveillance data from the broader research programme were considered to interpret seasonal transmission. Aedes breeding habitats were documented, with particular attention to water-storage containers, tanks and other artificial receptacles. Results: A total of 5,142 dengue cases were recorded across the selected districts during 2015–2019, of which 3,785 occurred in the semi-arid group. Jaisalmer and Jodhpur showed the highest reported incidence within the arid and semi-arid groups, respectively, whereas Bikaner and Hanumangarh showed the lowest incidence in their respective groups. Entomological observations demonstrated the persistence of Aedes aegypti in domestic and peri-domestic habitats despite the semi-arid environmental conditions. Water-storage containers, tanks and artificial receptacles represented important breeding environments. The broader Jodhpur investigation further demonstrated seasonal dengue peaks during the post-monsoon period and associations with temperature and relative humidity. Conclusion: Dengue transmission in arid and semi-arid Rajasthan is supported by the interaction of seasonal environmental conditions and anthropogenic water-storage practices that provide breeding opportunities for Aedes aegypti. Public-health risk management in such environments should integrate climatic surveillance with targeted inspection and management of domestic and peri-domestic water-holding habitats.