Objective To understand the composition and distribution of plague-related host animals and vector insects, as well as the incidence level of plague in Tengchong, Yunnan province, evaluate the risk of local plague epidemic, and provide evidence for plague surveillance and prevention.

Methods From 2021 to 2022, the small mammals in three different habitats of residential area, agricultural area and forest area in Tengchong were investigated and captured by night trapping method and cage night method. The parasitic fleas on the body surface of small mammals were collected, and the morphological classification and identification of small mammals and the parasitic fleas were carried out. The composition ratio, capture rate, flea infection rate and flea index were calculated. The organs of the small mammals and parasitic fleas of small mammals were used for Yersinia pestis isolation and culture. Meanwhile, the serum of plague index animals and the serum of local residents and serum of live mice were collected for the detection of plague F1 antibody by indirect hemagglutination assay (IHA) .

Results A total of 583 rodents, belonging to 26 species, 16 genera, 6 families and 4 orders, were captured, and the capture rate was 8.42%. The predominant species were Rattus tanezumi and Rattus andamanensis, accounting for 19.21% and 10.29%, respectively. Rattus tanezumi was the absolute predominant species in residential areas, accounting for 85.96%. Micromys minutus, Rattus tanezumi, Anourosorex squamipes and Rattus nitidus were the predominant species in agricultural areas, and Suncus murinu, Niviventer fulvescens, Rattus andamanensis,Mus pahari and Niviventer confucianu were the predominant species in forest areas. There were significant differences in the capture rate of rodents among residential areas, agricultural areas and forest areas. A total of 210 fleas, belonging to 16 species, 10 genera and 5 families were captured. The overall infection rate in the fleas was 15.95%, and the total flea index was 0.36. The flea index of Anourosorex squamipes (1.19) and Rattus tanezumi (0.78) were relatively high. The predominant flea species were Palaeopsylla remote, Leptopsylla segnis, Neopsylla stevensi sichuanyunnana and Xenopsylla cheopis, accounting for 23.33%, 22.86%, 16.67% and 12.86%, respectively. The highest flea infection rate and flea index were 29.82% and 1.33 in residential areas. No Y.pestis was detected in 556 animal organs and 210 fleas by etiological detection. The serological detection indicated that 201 serum samples of index animals (dogs, cats) and 76 serum samples of live mice were negative. One of the 430 serum samples from the local residents was positive for plague F1 antibody. No evidence of recent animal and human plague epidemics was found in the epidemiological survey.

Conclusion Abundant species of rodents and their parasitic fleas exist in Tengchong. The main hosts and vectors of plague in domestic rats are predominant species and widely distributed. Although no evidence of plague epidemic was found, there is a risk of local small spread. It is still necessary to strengthen surveillance and carry out prevention and control in a timely manner to effectively reduce the risk of epidemic.