Investigation of Ectoparasitic Chigger Mites on Eothenomys miletus in Dali of Yunnan

Objective To investigate the distribution of ectoparasitic chigger mites on the body surface of Eothenomys miletus (a species of wild rats), the chigger mite community and the spatial distribution pattern of the dominant mite species. Methods Different areas surrounding the Erhai Lake in Dali of Yunnan, China were selected as investigated spots. The rat hosts (E.miletus) were randomly captured with baited mouse cages. Chigger mite samples were collected from two auricles of every rat host. All the chigger mites on the surface of two auricles were scraped off by a bistoury at first and then preserved in 70% of ethanol. Hoyer's medium was used to mount the chigger mites onto glass slides and the specimens of the chigger mites on the slides were finally identified into species under a microscope. Richness (S), Shannon-Wiener's diversity index (H′), evenness (J′) and dominance index (C′) were adopted to measure the community structure of chigger mites on the rat hosts. Some simple indices were used to judge the spatial distribution patterns of the dominant chigger mite species among the different individuals of their rat hosts (E.miletus). The adopted indices are dispersing coefficient (C), Cassie index (CA), Clumping index(I) and Patch index (m,/m). Results 29858 individuals of chigger mites were collected from916 captured rat hosts (E.miletus). All the chigger mites were identified as 51 species and 8 genera in 3 subfamilies in Trombiculidae. Of 51 chigger mite species,6 main mite species accounts for 81.29% of the total mites, and their mite infestation rates and mite indices are high. The chigger mite community on E.miletus is composed of abundant species of chigger mites with a high diversity index and evenness,but low dominance index. Six dominant species of chigger mites are all judged as an aggregated distribution pattern among the different individuals of their rat hosts, E.miletus. Conclusions The parasitism of chigger mites on the body surface of E.miletus is very common in the surrounding areas of Erhai Lake in Dali of Yunnan with a heavy burden of the mites. The community of chigger mites on E.miletus is quite complicated with abundant mite species and a high community diversity. The main species of chigger mites tends to aggregate on the body surface (especially auricles) of E.miletus to form various mite groups.