Infestation and distribution of chiggers on Ryukyu mouse in southwest China

Chiggers are a group of ectoparasites and they are the vector of scrub typhus. Although the Ryukyu mouse ( Mus caroli ) is a common species of rodent in some outdoor habitats, few studies are about the mouse itself and its ectoparasites. To date, there has been no specific report on chiggers of M. caroli . Based on the field investigation in southwest China from 2001 to 2019, this paper reported the infestation and distribution of chiggers on M. caroli for the first time. Among the 91 sites investigated, 263 Ryukyu mice were captured at 18 sites, and 678 chiggers were collected from the mice. The collected chiggers were identified to be one family, two subfamilies, six genera, and 16 species with relatively low species diversity. The overall infestation prevalence ( P M ), mean abundance ( MA ), and mean intensity ( MI ) were P M = 27.38%, MA = 2.58 chiggers/per mouse, and MI = 9.42 chiggers/per mouse respectively. The dominant chigger species are Walchia ewingi and W. micropelta with a total constituent ratio of C r = 94.10% (638/678), and they were of aggregated distribution among different individuals of the host M. caroli . The distribution of two dominant chigger species seemed to be mutually independent with the association coefficient V ≈ 0 ( p < 0.001). The infestation ( P M , MA , and MI ) of M. caroli with chiggers greatly fluctuated in different geographical landscapes, altitudes, and latitudes with an obvious environmental heterogeneity. The male and adult M. caroli harbored much more chigger mites with significantly higher infestations ( P M , MA and MI ) than the female and juvenile mice. The theoretical curve of species abundance distribution of the chigger mite community on M. caroli was fitted by Preston lognormal distribution model with fitting goodness R 2 = 0.77. Based on the iChao 1 formula, the expected total number of chigger species on the mice was estimated to be 24 species.