Species Diversity of Brucella spp. Infecting Humans in Tongliao City, China
- 1 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 2 Department for Infectious Disease Control, Mudanjiang Municipal Center for Disease Control and Prevention, Mudanjiang, China
- 3 Department for Endemic Disease Control, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 4 Department for General Outpatient, Tongliao Municipal Center for Disease Control and Prevention, Tongliao, China
- 5 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 6 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 7 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 8 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 9 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 10 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 11 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 12 Microbiology Laboratory, Tongliao Municipal Disease Prevention and Control Center, Tongliao, China
- 13 National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
- 14 Mongolian Medicine Research Laboratory, Tongliao Mongolian Medical Hospital (Tongliao Mongolian Medical Research Institute), Tongliao, China
Abstract
O bjective : Human brucellosis poses a substantial public health threat in Tongliao; however, the species diversity of Brucella strains infecting humans remains unclear. Methods : A cross-sectional study was conducted among consecutive outpatients at a brucellosis hospital (August-September 2024). Demographic, clinical, and symptom data were collected via questionnaire. Serum samples were tested with SAT, and Brucella species/biovars were identified by nested-PCR. Sequencing data were used for phylogenetic analysis (neighbor-joining tree) to assess strain clustering. Results : The cohort comprised 42.17% (97/230) initial cases, 53.48% (123/230) follow-up cases, and 4.35% (10/230) health examiners. Clinical presentations included fever only (10.43%), fever with limb soreness (18.26%), limb soreness only (43.91%), and asymptomatic infection (26.96%). Serologically, 23.04% (53/230) had serum agglutination test (SAT) titers ≥ 1:100, 22.17% (51/230) had titers of 1:25 - 1:50, and 33.91% (78/230) were negative. Nearly half (49.57%, 114/230) had taken medication prior to consultation. Brucella was detected in 43.48% (100/230) of cases by nested-PCR. Species distribution among positive samples was B . abortus (70.00%), B . melitensis (11.74%), and B . suis (3.00%), with multiple biovars identified for each species. Phylogenetic analysis of 100 sequences resolved them into 9 distinct clades (Groups 1 - 9), revealing clear biovar-clade associations: B . abortus biovar 1 clustered in Groups 1 and 8, biovar 2 in Group 2; B . melitensis biovars 1, 2, and 3 were respectively assigned to Groups 5, 4, and 3/9; B . suis biovars 1 and 2 were placed in Groups 6 and 7. Conclusion : This study first reveals the high species and genetic diversity of Brucella infecting humans in Tongliao, showing a dominance by B . abortus with co-circulation of B . melitensis and B . suis . The high diversity indicates complex epidemic origins and control challenges, calling for integrated strategies and enhanced molecular surveillance.
- Fernandez-Georges, I.K., Manalo, S.M., Arede, M., Ciaravino, G., Beltrán-Alcrudo, D., Casal, J., et al . (2025) Ruminant and Human Brucellosis Situation in Türkiye and the Caucasus. Tropical Animal Health and Production , 57, Article No. 296. https://doi.org/10.1007/s11250-025-04525-1
- Bao, G.Y., Chen, J.J., Zhang, T.C., et al . (2023) Relationship of Brucella in Blood with Clinical Symptoms and Antibody Levels in Brucellosis. Disease Surveillance , 38, 432-435. (in Chinese)
- Harrison, E.R. and Posada, R. (2018) Brucellosis. Pediatrics in Review , 39, 222-224. https://doi.org/10.1542/pir.2017-0126
- Yin, C., Yang, C., Wu, Y., Di, J., Bai, T., Wang, Y., et al . (2025) Molecular Epidemiology of Brucella spp. in Aborted Livestock in the Ningxia Hui Autonomous Region, China. Veterinary Sciences , 12, Article 702. https://doi.org/10.3390/vetsci12080702
- Statistical Bulletin on National Economic and Social Development of Tongliao City in 2024. (in Chinese)
- Cui, B.Y. and Jiang, H. (2018) Surveillance Data of Brucellosis in China, 2005-2016. Disease Surveillance , 33, 188-192. (in Chinese)
- Osoro, E.M., Munyua, P., Omulo, S., Ogola, E., Ade, F., Mbatha, P., et al . (2015) Strong Association between Human and Animal Brucella Seropositivity in a Linked Study in Kenya, 2012-2013. The American Society of Tropical Medicine and Hygiene , 93, 224-231. https://doi.org/10.4269/ajtmh.15-0113
- Tian, G.Z., Lu, D.Y., Piao, D.R., et al . (2019) Epidemiological Characteristics of Brucella Species Isolated from Different Regions of the World Using the MLVA Genotyping. Chinese Journal of Epidemiology , 40, 676-681. (in Chinese)
- Jiang, S.Q. (1986) Handbook for Prevention and Control of Brucellosis. People’s Health Publishing House.
- Tian, G.Z. (2021) A Nested-Polymerase Chain Reaction Assay to Identify and Genotype Brucella . Biomedical and Environmental Sciences , 34, 227-231.
- Franco, M.P., Mulder, M., Gilman, R.H. and Smits, H.L. (2007) Human Brucellosis. The Lancet Infectious Diseases , 7, 775-786. https://doi.org/10.1016/s1473-3099(07)70286-4
- Liu, Z.G., Gao, L.P., Wang, M., Du, S.N., Yuan, M. and Li, Z.J. (2025) Global Species/Biovars and Genotype Diversity Atlas of Brucella spp.-102 Countries, 1923-2020. China CDC Wkly , 7, 144-151.
- Araj, G.F. (2010) Update on Laboratory Diagnosis of Human Brucellosis. International Journal of Antimicrobial Agents , 36, S12-S17. https://doi.org/10.1016/j.ijantimicag.2010.06.014