A study on Tibetan sheep in the Gansu plague-endemic area and the risk of plague transmission by their vectors

BACKGROUND: In the Qinghai-Tibet Plateau region, Tibetan sheep can contract plague by licking the carcasses of dead marmots or through flea bites. In recent years, pastoral areas in Gansu Province that are designated as plague foci have introduced Tibetan sheep on a large scale, increasing the risk of plague outbreaks. This study aims to clarify the current status of plague outbreaks among Tibetan sheep in the Himalayan marmot plague foci of Gansu Province and their exposure to vectors, and to systematically assess the risk of plague occurrence and transmission among Tibetan sheep in these foci. Based on these findings, targeted risk control measures will be proposed to provide a scientific basis for decision-making aimed at containing plague outbreaks and safeguarding public health and social stability. METHODS: Subei Mongol Autonomous County, one of the Himalayan marmot plague foci in Gansu Province, was selected as the sampling area. Blood, nasal swabs, and ectoparasite samples were collected from Tibetan sheep across different seasons. Samples were tested using a variety of methods, including serology (IHA), molecular biology (PCR), microbiology (bacterial culture), and ectoparasite identification. Combining these results with concurrent plague surveillance data from the sampling area, ArcGIS was used to analyze the distribution of sampling sites and their spatial relationship with animal disease hotspots, and SPSS software was employed to comprehensively evaluate the plague infection status of Tibetan sheep in this endemic area. RESULTS: A total of 3,033 Tibetan sheep from 35 herds across 9 villages were sampled.10 blood samples tested positive for plague F1 antibodies, with a detection rate of 3.33‰ (10/3033). Antibody titers ranged from 1:16 to 1:128. Spatial analysis revealed that the median distance from plague bacterium detection sites to positive F1 antibody sites during the same period was shorter than the distance to negative sites. Ectoparasites were detected on the body surfaces of 21 Tibetan sheep, with a detection rate of 0.7% (21/3033); 6 hard ticks (Ixodidae) and 30 mites (Acari) were identified. Laboratory testing revealed that 1,090 nasal swabs, 36 ectoparasite samples, and bacterial cultures were all negative. CONCLUSION: This study is the first to confirm the presence of plague infection in Tibetan sheep within the plague-endemic areas of Gansu Province. If Tibetan sheep come into contact with infected animals or pathogen-carrying vectors and subsequently enter the trade and distribution channels, it will pose unpredictable public health risks. It is recommended that Tibetan sheep be included in the plague surveillance system, with random sampling of relevant materials; health education and control measures for high-risk populations should be strengthened; and further research on plague in Tibetan sheep should be conducted to provide a theoretical basis for optimizing plague prevention and control strategies.