Distribution and host selection of the chigger mite vector of scrub typhus,Leptotrombidium deliense, in southwest China

Leptotrombidium deliense (Walch) is believed to be the most important vector of scrub typhus in China. From 2001–2019, a long-term investigation was made in 82 counties of southwestern China, covering five provincial divisions: Yunnan, Guizhou, Sichuan, Tibet and Chongqing. The results showed that L. deliense was not the most dominant chigger species in southwestern China. A total of 8,385 L. deliense were collected from 13 counties, which accounted for only 5.42% of all the identified chiggers (299 species with 154,665 individuals). Leptotrombidium deliense was mainly distributed in the low latitude (21–22°N: 48.16%), low elevation (<1000 m: 81.75%), flat landscape (70.14%) and outdoor habitat (90.66%). Although 73.98% of L. deliense were collected from the Asian house rat (Rattus tanezumi), the mite had low host specificity, being collected from 22 species of rodents and other small mammals across different species, genera, families and orders. Leptotrombidium deliense was of an aggregated distribution among its animal hosts.