Distribution and Host Selection of the Chigger Mite <i>Leptotrombidium rupestre</i> , a Potential Vector of Scrub Typhus, in Southwest China

Leptotrombidium rupestre, a chigger species, is a potential vector of scrub typhus. Based on field surveys in southwest China between 2001 and 2022, this paper retrospectively reports the distribution and host selection of L. rupestre in the region for the first time. A total of 4675 L. rupestre were identified from 28 species of rodents and other sympatric small mammal hosts in 23 out of 114 survey sites, and it was mainly distributed in higher latitudes (31-33° N) and altitudes (3000-3500 m), especially in western Sichuan, an important focus of scrub typhus. Among four orders of hosts, 96.15% (4495/4675) of L. rupestre were found on the order Rodentia. At species level of hosts, 40.49% of L. rupestre (C_r = 40.49%, 1893/4675) came from the vole Alexandromys oeconomus in Cricetida of Rodentia, with high prevalence (P_M = 91.67%), mean abundance (MA = 157.75 chiggers/per examined vole) and mean intensity (MI = 172.09 chiggers/per infested vole), indicating an obvious host-preference. L. rupestre was of aggregated distribution among different individuals of the hosts. The occurrence of L. rupestre in western Sichuan may increase the potential risk of the focus persistence of scrub typhus in the region. The present study enriches scientific information on this potential vector species and will contribute to the surveillance and control of scrub typhus in the future.