One Health assessment of chigger mite diversity, host ecology and scrub typhus risk in Southern Rajasthan, India

Scrub typhus is an important vector-borne zoonosis caused by Orientia tsutsugamushi and transmitted by trombiculid mite larvae (chiggers), with increasing relevance to One Health owing to its complex interactions among vectors, wildlife reservoirs, domestic animals, and humans across South and Southeast Asia. Despite the increasing burden of scrub typhus in Rajasthan, the trombiculid fauna and its ecological associations with small mammal communities in the semi-arid Aravalli landscape remain poorly characterized. The present study conducted a systematic two-year eco-epidemiological survey (June 2024-May 2026) across eight tehsils of Udaipur district, Rajasthan, India, deploying 1,440 traps to assess host trapping dynamics, chigger species diversity, host-specific infestation profiles, tribal composition, dominance status, and spatio-temporal distribution patterns of trombiculid mites. A total of 512 small mammals belonging to seven species were examined, yielding an overall trap positivity rate of 35.56% and a chigger infestation prevalence of 29.10%. Eight chigger mite species belonging to three tribes Trombiculini, Schoengastiini, and Gahrlipiini under subfamily Trombiculinae were identified, with tribe Trombiculini exhibiting the highest species richness. Suncus murinus emerged as the primary reservoir host, recording the highest infestation prevalence (42.33%), maximum chigger burden, and broadest associated species diversity. Leptotrombidium deliense and Ascoschoengastia indica were the dominant and most ecologically generalized chigger species across multiple study sites. Marked seasonal variation was observed, with monsoon and post-monsoon periods recording significantly elevated trap positivity and infestation indices. These findings establish Udaipur district as an active eco-epidemiological zone for chigger-mediated zoonotic transmission and support integrated One Health surveillance strategies in semi-arid India.