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Objective: To investigate species composition of chigger mites on Rattus flavipectus in different zoogeographical subregion of Yunnan Province., Methods: The field investigation was carried out in 25 counties of Yunnan Province during 2001-2012. Some conventional statistical methods were adopted to calculate the species of collected chigger mites, constituent ratio (Dr), mite infestation rate (RM), mean abundance (MA), mean intensity (MI), species richness (S) and species diversity index (H') of chigger mites in five zoogeographical subregions. The hierarchical cluster analysis was used to compare the similarity of chigger mite communities on the rats in the subregions., Results: A total of 2 118 R. flavipectus were captured. 11 040 individuals of chigger mites were identified as 3 subfamilies, 17 genera and 114 species. The overall RM, MA and MI of chigger mites were 19.6% (416/2 118), 5.2 mites per examined rat and 26.5 mites per infested rat, respectively. The species richness, species composition and dominant species of chigger mites on R. flavipectus were not identical among the subregions. The RM (28.9%, 179/620), MA (10.6) and MI (36.6) of chigger mites in the mountainous subregion of southern Yunnan were the highest among the five subregions. There was a significantly linear positive correlation between the number of R. flavipectus and the species of chigger mites (r = 0.942, P < 0.05). The similarity of chigger mite communities between plateau subregion of western Yunnan and mountainous subregion of southern Yunnan was the highest, and the dominant species of chigger mites was Leptotrombidium deliense. The main dominant species of chigger mites in middle subregion and southern subregion of Hengduan Mountains, and eastern plateau subregion of Yunnan were Ascoschoengastia indica and Schoengastiella ligula., Conclusion: The infestation of chigger mites on R. flavipectus is common with a high species diversity. The composition of chigger mite community in different geographical subregions is significantly different.

During a survey lasting from 1990 to 2008, we captured 4,113 Asian house rats, Rattus tanezumi Temminck 1844 (Rodentia: Muridae) from 28 counties of Yunnan Province in southwestern China. From these rats, a total of 19,304 gamasid mites (Acari: Mesostigmata) were collected and identified as comprising 50 different species. The species diversity of gamasid mites from this single rat species is higher than that reported previously from multiple hosts within a given geographical region. Of the 50 mite species, 31 species belonged to ectoparasites and 19 species belonged to free-living mites. The species diversity of the mites from rats trapped outdoors was much higher than from rats trapped indoors. The parameter K from the negative binomial distribution was used to measure the spatial distribution patterns of the dominant mite species and revealed that all the mites had an aggregated distribution among the rat hosts. Most mite species showed a predominantly female-biased population structure with many more females than males.

Based on the field investigation in five provincial regions of Southwest China between 2001 and 2019, the present paper reports the infestation and distribution of chigger mites on the Confucian white-bellied rat Niviventer confucianus in China for the first time. A total of 11,017 chigger mites were collected from the body surface of 911 N. confucianus rat hosts, and 10,161 of them were identified as 166 species and 16 genera in three subfamilies under two families with high species diversity (S = 166, H' = 3.19, E = 0.62). Of 911 N. confucianus rats, 341 individuals were infested with chiggers with high overall prevalence (PM = 37.43%), mean abundance (MA = 12.09 mites/rat) and mean intensity (MI = 32.31 mites/rat). On the body surface of N. confucianus, Ascoschoengastia sifanga was the most dominant chigger species followed by Walchia ewingi and Leptotrombidium rupestre. All the three dominant chigger species showed an aggregated distribution pattern among different individuals of N. confucianus. Chigger infestations on the same rat host (N. confucianus) showed some heterogeneity under different environmental conditions such as latitudes, longitudes, altitudes and landscapes. Based on Preston's lognormal model, the species abundance distribution of chiggers on N. confucianus conformed to a lognormal distribution pattern, and the predicted total species of chiggers on N. confucianus in Southwest China was estimated to be 228 species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Ethnopharmacological relevance: Caesalpinia sappan is a medicinal plant native to China popularly used to treat chronic pelvic inflammation, dysmenorrhea and hysteromyoma. Its main bioactive component is brazilin which had presented antibacterial, anti-inflammatory and anti-platelet aggregation activities. To establish a sensitive, selective, reproducible, and accurate high performance liquid chromatographic (HPLC) method for the quantitative determination of brazilin in plasma, and study the pharmacokinetics of brazilin in rats after intravenous administration of brazilin. Materials and methods: Rats received intravenous injection of 25, 50 and 100mg/kg of brazilin. Concentrations of brazilin in plasma were determined by HPLC method at different time points and all pharmacokinetic parameters were estimated by non-compartmental analysis with WinNonLin 6.2 software. Results: After single intravenous doses of 25, 50 and 100mg/kg brazilin in rats, the main PK parameters were as follows: C max were 18.1±4.1, 46.7±8.7 and 82.2±9.6µg/mL; AUC0–24 were 20.4±4.3, 48.7±6.8 and 90.4±10.3µgh/mL; and t 1/2 were 5.4±1.5, 5.8±0.9 and 6.2±1.2h, respectively. Conclusion: It showed that the brazilin was eliminated moderately in rat by intravenous injection route with t 1/2 of 6h and showed a dose-dependence profile of C max and AUC0–24 at the doses of 25~100mg/kg of brazilin for injection in rats. [ABSTRACT FROM AUTHOR]