Infestation and distribution of chigger mites on Brown rat (Rattus norvegicus) in Yunnan Province, Southwest China

Chigger mites is a group of arthropods and some of them are vectors of scrub typhus. As a common synanthropic rodent species, the Brown rat (Rattus norvegicus) often harbors lots of ectoparasites including chigger mites. According to some "data mining" strategies, the present study took the advantage of the abundant original data from a long-term field ecological investigation between 2001 and 2015 to make a detailed analysis of chigger mites on R. norvegicus in Yunnan Province, Southwest of China. From 18 of 33 investigated counties, only 1414 chigger mites were collected from 1113 Brown rats with relatively low infestations. The 1414 individual chigger mites were identified as comprising 61 species, 11 genera and 2 subfamilies of the family Trombiculidae with a high species diversity (S=61, H'=3.13). Of 61 mite species, there were four main species, Walchia ewingi, Ascoschoengastia indica, W. koi and A. rattinorvegici, which accounted for 44.41% of the total mites. All the chigger mites were of aggregated distribution among different individuals of R. norvegicus. The Brown rats in the outdoor habitats harbored much more individuals and species of chigger mites with a higher mean abundance (MA=1.46) and mean intensity (MI=12.53) than in the indoor habitats (P<0.05). The overall infestation of the rats was significantly higher in the mountainous landscapes than in the flatland landscapes (P<0.001). The species similarity (C_ss) of the mites on the male and female rats reached 64.44% with sex biased infestations. The male rats harbored more species and individuals of the mites than the female rats. The adult rats harbored more species and individuals of the mites than the juvenile rats. The species abundance distribution of the mites was successfully fitted by Preston's lognormal model with ŝ(R)=15e^{-[0.31(R-1)]2} (α=0.31, R²=0.95). On the basis of fitting the theoretical curve by Preston's model, the total mite species on R. norvegicus was estimated to be 86 species, and 25 rare mite species were missed in the sampling field investigation. The curve tendency of the species-plot relationship indicates that R. norvegicus have a great potential to harbor many species of chigger mites, and more species of the mites would be collected if more rats are sampled.

Osteoblast MC3T3-E1 Culture on a Fast-setting Carbonated Hydroxyapatite Bone-like Material

Using ultra-fine grain technology, a fast-setting type of carbonated hydroxyapatite (CHA) material from Ca3(PO4)2·3H2O (ACP), CaCO3, Ca(H2PO4)2 (MCPA) and Na3PO4 was prepared. The ultra-fine particles (3 m) shortens the setting time, to form bone like material with 5.2wt% carbonation. Osteoblastic MC3T3-E1 cells were cultured with CHA material to observe cell adhesion, proliferation and differentiation. There were no obvious differences in adhesion and proliferation rate of MC3T3-E1 cells between the CHA and the control group. MC3T3-E1 cells on the surface of CHA observed by a scanning electron microscope (SEM). The alkaline phosphatase (ALP) activity of the cells on the CHA was higher than the control, and collagen I (COL 1) mRNA expressed on the CHA was also significantly higher than the control. This CHA bone material exhibited biocompatibility and osteo-conductive properties that are sought for bone repair and scaffolding for tissue engineering. *Author to whom correspondence should be addressed.