Objective To investigate the changes in the number and composition of parasitic flea populations on wild rodents in the Zhangjiakou competition zone of the 24th Olympic Winter Games from 2018 to 2021, and to provide a basis for prediction and warning of rodent-borne diseases in the in Chongli district, Zhangjiakou competition zone. Methods Wild rodents were caught by the night traping method in Chongli district, Zhangjiakou city. Parasitic fleas on the rodents were collected and identified. Excel 2010 software was used to summarize the data and perform year-by-year and month-by-month analyses. A chordal graph was used to present the relationship between wild rodents and parasitic fleas. The seasonal distribution of fleas was analyzed by the concentration degree method. Results From 2018 to 2021, a total of 302 rodents were caught in Chongli district, belonging to 11 species of 9 genera under 4 families. All rodent species but Mus musculus carried fleas. A total of 218 fleas were collected, belonging to 13 species of 8 genera under 4 families. The average flea index was 0.72. The most dominant flea species was Amphipsylla vinogradovi, which had the closest relationship with Cricetulus barabensis and was also found on other seven rodent species including C. longicaudatus, Tscherskia triton, and Apodemus agrarius. Strong seasonality (all M=0.72) was observed in total, male, and female parasitic fleas on wild rodents. Conclusion Parasitic fleas on wild rodents in Zhangjiakou competition zone have large quantities, diverse species, and strong seasonality, with a close relationship with C. barabensis. Their population density and structure changes should be a warning in key areas. Attention should be paid to the trend and complications of rodent-borne disease epidemics.

Objective To understand the changes in the size and structure of small mammals populations from 2018 to 2021 in the Zhangjiakou competition zone of the 24th Winter Olympic Games, and to provide the basis for the prediction and warning of small mammals-related diseases in this area. Methods Field investigation of small mammals was carried out in two towns and eight townships of Chongli district, which are the locations of facilities of the Zhangjiakou competition zone of the 24th Winter Olympic Games. Using the 5 m clamp line method, 6-8 sampling sites were selected randomly every month, and 1-2 representative habitats with different type or altitude were selected at each site (100 mousetraps per habitat). Excel 2010 software was used to summarize the monthly and yearly survey data of small mammals. By using the methods of concentration degree and linear correlation, the seasonal distribution of small mammals and the distribution characteristics in different habitats were analyzed. Results In 2018-2021, 438 small mammals (hereinafter referred to as rodents) were captured using 33 610 clamp-times, with an average capture rate of 1.30%. The rodents belonged to 2 orders, 4 families, 9 genera, and 12 species, with Apodemus agrarius as the dominant species (125, 28.54%). The year with the highest rodent density was 2019, and the capture rate was 2.09%. The year with the highest number of rodent species was 2020, and 12 species were captured. The density of rodents showed large seasonal variations ( M=0.58) in a bimodal pattern, with the first peak in March of spring and the second peak in August of autumn. The species of rodent showed seasonal variations ( M=0.31) in a unimodal pattern. The density of rodents increased with elevation, and the capture rate was 0.22% (low elevation), 1.06% (medium elevation), and 2.00% (moderately high elevation). Most species of rodents were captured at medium elevation (10 species), followed by moderately high elevation (4 species) and low elevation (3 species). There was a positive correlation between rodent density and species in different habitats ( r=0.823, P=0.006). The changes of rodent density and species were most significant in grassland, farmland, forest belt, and hillside. Conclusion In the Chongli district in Zhangjiakou competition zone of the 24th Winter Olympic Games, rodents have high population, rich species composition, and strong seasonal variation. The distribution of rodents in different habitats showed specific patterns. The changes in rodent density and species composition in key areas should be monitored. Attention should be paid to epidemic trend of rodent-borne diseases and the important influence of their transmission.

Objective To investigate the changes in species composition and number of small rodents in natural plague foci of Hebei province, China, from 1990 to 2020, and to provide a basis for the prediction and early warning of animal epidemics in the plague foci. Methods Excel 2010 software was used to summarize and count the monthly and annual surveillance data on small rodents, and the concentration degree method was used to analyze the seasonal distribution of small rodents. Results From 1990 to 2020, a total of 112 205 clamps were placed and 1 322 rodents were caught, with a mean capture rate of 1.18%. The highest capture rate (2.30%) occurred in the year 2019, followed by the year 2004 (2.20%), and the lowest capture rate (0.41%) occurred in the year 2000. There were 9 years (1990, 1999, 2004, 2012-2016, and 2019) when the capture rate was higher than the mean value. A total of 11 species of rodents were captured, belonging to 8 genera and 4 families, among which Cricetulus barabensis (63.31%) was the dominant species. The highest number of small rodent species (8 species) was observed in 2014, and the fewest (1 species) in 1991. The number of small rodents were distributed evenly throughout the year ( M=0.13), and the months with relative high numbers were June (247/1 322, 18.68%), July (259/1 322, 19.59%), and October (250/1 322, 18.91%). The interannual distribution of the number of the dominant species, C. barabensis, had been consistent with that of small rodents, with the highest number seen in 2019. The number distribution of C. barabensis showed seasonality ( M=0.30) and the number was relatively high in summer and autumn, with the highest number in October (0.98%), followed by July (0.82%), June (0.71%), and November (0.71%). Conclusion The species number of small rodents has a rising tendency, with rich species composition. The significant influence of the changing trend in the small rodent species on rodent epidemic outbreaks and spread should be highlighted.