Discovery and confirmation of Altay Mountain plague focus in Xinjiang Uygur Autonomous Region

  Objective  To investigate and confirm the existence of natural focus of plague in Altay Mountain of Xinjiang Uygur Autonomous Region.

  Methods  The plague focus investigation were carried out in Altay Mountain area, Qinghe, Fuhai, Altay, during 2021−2022. The experimental methods included bacteriological, serological, molecular biological identification assays in specimens (rodent organs, serum, heart infusion, vector parasitic fleas). In addition, biochemical type of Yersinia pestis isolates was identified.

  Results  A total of 115 rodents, including dead ones, and 136 vector parasitic fleas were captured in Altay Mountains area. In the rodents, the predominant species were C. undulates and Marmota baibacina, accounting for 60.87% and 20.87%, respectively. In the parasitic fleas, the predominant species were Citellophilus tesquorum altaicus and Oropsylla silantiewi, accounting for 67.74% and 100.00%, respectively. A total of 86 serum samples, 21 samples of heart infusion of small mouse, 8 samples of dead rodent organ grinding fluid were tested through bacteriological, immunological methods, and 8 DNA samples extracted from dead rodent organ tissues were detected by real-time PCR. One F1 antibody positive serum sample of C. undulates was detected, the titer of indirect hemagglutination assay (IHA) was 1∶128 and the titer of ELISA was 1∶256. One positive sample of plague F1 antigen was detected in the grinding fluid of dead M. baibacina organ, the titer of reverse indirect hemagglutination assay (RIHA) was 1∶64, and titer of enzyme linked immunosorbent assay (ELISA) was 1∶128. Two positive samples of plague F1 antigen were detected in dead C. undulates organ grinding fluid, the titers of RIHA were 1∶512 and 1∶1 024; the titers of ELISA were 1∶2 048 and 1∶4 096 respectively. Plague special real-time PCR detected 2 positive samples in C. undulates organ tissues. Two strains of Y. pestis were isolated and corresponding biovars were identified as Antique type.

  Conclusion  A new plague focus was identified in the Altay Mountain area of Xinjiang and the biochemical types belonged to Antique.