Objective: To investigate the geographical distribution and host selection of Leptotrombidium rubellum among different small mammal hosts in some areas of Yunnan province, China.
Methods: Field survey was carried out in 23 counties of Yunnan province between 2001 and 2011. Small mammal hosts were captured with mouse cages and traps with baits. Chigger mites on the surface of two auricles were scraped off by a bistoury, and then preserved in 70% ethanol. Every specimen of the chigger mites on the slides was finally identified into species under a microscope. Some conventional statistical methods were adopted to calculate all the collected chigger mite species and the constituent ratios of L. rubellum in different areas and on different hosts, with prevalence (P), mean intensity (MI) and mean abundance (MA) on different hosts calculated. Linear regression was used to analyze the relationship among P, MI and MA. Patch index (m*/m) was used to measure the spatial patterns of L. rubellum among different individuals of related small mammal hosts.
Results: A total of 108 480 chigger mites were collected from the body surface of all the captured small mammal hosts. All the collected chigger mites were identified as 3 subfamilies, 24 genera and 234 species. Of the 234 species of chigger mites, 654 individuals of L. rubellum were collected, only in 4 counties. The collected individuals of L. rubellum accounted for 0.603% of the total mites (108 480 individuals). 96.637% of L. rubellum came from flatland areas and habitats while only 3.363% of the L. rubellum were from the mountainous regions. The orderings of the hosts appeared as Rodentia and Insectivora harbored 96.296% and 2.469% respectively, of the collected while Lagomorpha and other orders there was no L. rubellum found. Of 67 species (in 34 genera and 12 families of 5 orders), Rattus tanezumi (in genus Rattus and family Muridae of Rodentia) harbored 96.788% of the collected L. rubellum with relatively low prevalence (P = 3.776%) or mean intensity (MI = 8.792 mites/per host), followed by Bandicota indica. Data from the patch index showed that L. rubellum had an aggregated distribution pattern among different individuals of their hosts.
Conclusion: L. rubellum existed in Yunnan province with relatively rare numbers of the individuals. In Yunnan province, L. rubellum was mainly found in the flatland regions and habitats with relatively low altitude. L. rubellum could parasitize several different species of hosts with low host specificity, but it prefered to choose Rattus tanezumi and some other house-dwelling small mammals as its main hosts.