Spatiotemporal Characteristics and Risk Zonation Analysis of Rodents and Surface-Parasitic Fleas - Inner Mongolia Autonomous Region, China, 2013-2021.

Background: Recent plague cases in Inner Mongolia prompted research on rodents and fleas. This study aimed to describe the spatiotemporal characteristics of parasitic fleas on predominant rodent species and identify plague risk areas.

Methods: We assembled monitoring data from the National Plague Surveillance System for 12 regions in Inner Mongolia from 2013 to 2021. We performed descriptive statistics using relative indices, analyzed interannual flea index trends using the Mann-Kendall test, compared spatiotemporal characteristics using the Kruskal-Wallis H test and Dunn's test, and delineated plague risk areas based on cluster analysis.

Results: In total, 134,181 rodents from 28 species were captured, with an average parasitism rate of 31.46%. A total of 143,958 fleas were collected, resulting in a total average flea index of 1.07. The primary rodent species were the Mongolian gerbil ( Meriones unguiculatus) and Daurian ground squirrel (Spermophilus dauricus). The flea index showed a decreasing trend (Sen's slope=-0.06, P<0.05). Meriones unguiculatus had two peaks (May and October), with a delay of one to two months after peak flea parasitism. Spermophilus dauricus had a peak in May but two flea parasitism peaks (March and November). Meriones unguiculatus and Spermophilus dauricus flea indices varied significantly across regions (H=25.75, P<0.001; H=29.88, P<0.001). Erdos City and Xilingol League had the highest flea indices for each species, respectively. Cluster analysis divided the 12 regions into three risk zones.

Conclusions: The two predominant rodent species in Inner Mongolia have demonstrated an overall decline in flea index over time. The hotspots for flea index are primarily concentrated in Erdos and Xilingol League. Strengthening regional cooperation is crucial for tailored plague prevention and control measures.