Study of Circulation of Leptospirosis Pathogens in Different Regions of Vietnam

The territory of South-East Asia, including Vietnam, is one of the disadvantaged in relation to leptospirosis areas. According to studies, 10 % of the Vietnamese population is infected with Leptospira, but at the same time, information about circulating Leptospira species, the main carriers of infection in various regions of Vietnam, is very limited. The aim of the work was to investigate the circulation of leptospirosis pathogens in various provinces of Vietnam, for which a study of suspensions of small mammalian organs was conducted, and the level of the immune stratum of the population living in the surveyed territories was determined. Materials and methods. The work was carried out on the base of the mobile laboratory for monitoring and diagnostics, as well as the Laboratory of Toxicology and Tropical Diseases of the Institute of Tropical Medicine. Molecular-genetic methods (PCR and sequencing) were used to study 2,790 samples of suspensions of small mammalian organs collected in 14 provinces located in the northern, central and southern parts of the country between 2019 and 2024. Additionally, 576 sera from conditionally healthy people, obtained in 5 northern provinces of Vietnam, were studied by ELISA to assess the intensity of immunity to Leptospira. Markers of pathogenic Leptospira were detected in 282 samples from 20 different species of small mammals using PCR, while positive results were obtained in samples from all the provinces studied. 76 positive samples were sequenced, as a result of which appurtenance to the species Leptospira interrogans, Leptospira borgpetersenii, Leptospira mayottensis was established. Specific IgG class antibodies to Leptospira were detected in 8.0 % of the cases. A risk group has been identified – people employed in agriculture. The results obtained show the ubiquitous spread of leptospirosis pathogens in Vietnam. A promising field of research is the zoning of the country’s territories according to the intensity of epidemic manifestations of leptospirosis, the determination of the species composition of circulating Leptospira and the main carriers among mammals, taking into account the landscape, geographical and socio-economic factors.

1. Soboleva G.L., Ananyina Y.V., Nepoklonova I.V. [Actual problems of human and animal leptospirosis]. Rossijskij Veterinarny Zhurnal [Russian Veterinary Journal]. 2017; (8):14–8.

2. Dunay S., Bass J., Stremick J. Leptospirosis: a global health burden in review. EmergMed (Los Angels). 2016; 6:(5):336. DOI: 10.4172/2165-7548.1000336.

3. Tokarevich N.K., Blinova O.V. [Leptospirosis in Vietnam]. Infektsiya i Immunitet [Russian Journal of Infection and Immunity]. 2022; 12(6):1019–28. DOI: 10.15789/2220-7619-LIV-1988.

4. Koizumi N., Morita M., Pheng V., Wann C., Masuoka H., Higa Y., Wada T., Hirayama K., Ohnishi M., Miura K. Rat trade and leptospirosis: Molecular epidemiology of Leptospira species in rats exported from Cambodia to Vietnam. Transbound Emerg. Dis. 2022; 69(3):1641–8. DOI: 10.1111/tbed.14077.

5. Boqvist S., Chau B.L., Gunnarsson A., Olsson Engvall E., Vågsholm I., Magnusson U. Animaland herd-level risk factors for leptospiral seropositivity among sows in the Mekong delta, Vietnam. Prev. Vet. Med. 2002; 53(3):233–45. DOI: 10.1016/s0167-5877(01)00263-x.

6. Bierque E., Thibeaux R., Girault D., Soupé-Gilbert M.E., Goarant C. A systematic review of Leptospira in water and soil environments. PLoS One. 2020; 15(1):e0227055. DOI: 10.1371/journal. pone.0227055.

7. Naidenova E.V., Kartashov M.Yu., Boyko A.V., Safronov V.A., Lopatin A.A., Kutyrev I.V., Bacar I., Boumbaly S., Kolomoets E.V., Kalivogui S., Boiro M.Y., Shcherbakova S.A. [Determination of the level of the immune stratum of the population of the Republic of Guinea to the causative agents of leptospirosis]. Epidemiologiya i Infektsionnye Bolezni. Aktual’nye Voprosy [Epidemiology and Infectious Diseases. Current Issues]. 2019; (2):39–43. DOI: 10.18565/epidem.2019.9.2.39-43.

8. Lunde D., Nguyen Truong Son. An Identification Guide to the Rodents of Viet Nam. New York: Center for Biodiversity and Conservation, American Museum of Natural History; 2001. 80 p.

9. Kruskop S.V. Bats of Vietnam. Checklist and an Identification Manual. 2nd edition, revised and updated. Biodiversity of Vietnam Series. Moscow; 2013. 300 p., 70 fig., 52 photos, color paste.

10. Porshakov A.M., Chumachkova E.A., Kas’yan Zh.A., Oglodin E.G., Mo L., Cuong V., Toan Ch., Nga B. [Results of epizootiological survey on plague and other zoonotic infections in the northern provinces of the Socialist Republic of Vietnam during spring months of 2019]. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 2020; (1):133–8. DOI: 10.21055/0370-1069-2020-1-133-138.

11. Maitah K., Smutka L., Sahatqija J., Maitah M., Phuong Anh N. Rice as a determinant of vietnamese economic sustainability. Sustainability. 2020; 12(12):5123. DOI: 10.3390/su12125123.

12. Tran V.D., Mai L.T.P., Thu N.T., Linh B.K., Than P.D., Quyet N.T., Dung L.P., Mai T.N.P., Hanh N.T.M., Hai H., Duong T.N., Anh D.D. Seroprevalence and serovar distribution of Leptospirosis among healthy people in Vietnam: Results from a multi-center study. Clin. Epidemiol. Glob. Health. 2021; 10:100700. DOI: 10.1016/j.cegh.2021.100700.

13. Chumachkova E.A., Porshakov A.M., Luong T.M., Bui T.T., Dang T.V., Shcherbakova S.A. [Identification of contingents at risk of natural focal diseases in Vietnam using a questionnaire-based survey]. Zdorov’e Naseleniya i Sreda Obitaniya [Public Health and Life Environment]. 2023; 31(9):64–71. DOI: 10.35627/2219-5238/2023-31-9-64-71.

14. Della Rossa P., Tantrakarnapa K., Sutdan D., Kasetsinsombat K., Cosson J.F., Supputamongkol Y., Chaisiri K., Tran A., Supputamongkol S., Binot A., Lajaunie C., Morand S. Environmental factors and public health policy associated with human and rodent infection by leptospirosis: a land cover-based study in Nan province, Thailand. Epidemiol. Infect. 2016; 144(7):1550–62. DOI: 10.1017/S0950268815002903.

15. Sakundarno M., Bertolatti D., Maycock B., Spickett J., Dhaliwal S. Risk factors for leptospirosis infection in humans and implications for public health intervention in Indonesia and the AsiaPacific region. Asia Pac. J. Public Health. 2014; 26(1):15–32. DOI: 10.1177/1010539513498768.

16. Faisal S.M., McDonough S.P., Chang Y.-F. Leptospira: invasion, pathogenesis and persistence. In: Embers M.E., editor. The Pathogenic Spirochetes: Strategies for Evasion of Host Immunity and Persistence. Boston: Springer US; 2012. P. 143–72. DOI: 10.1007/978-1-4614-5404-5_8.

17. Haake D.A., Levett P.N. Leptospirosis in humans. Curr. Top. Microbiol. Immunol. 2015; 387:65–97. DOI: 10.1007/978-3-662-45059-8_5.

18. Managing Leptsopirosis outbreaks. A publication of Epidemiological Unit, Ministry of Healthcare & Nutrition Sri Lanka. Weekly Epidemiological Report. 2007; 34(47):1–2. (Cited 15 May 2025). [Internet]. Available from: https://www.epid.gov.lk/storage/post/pdfs/vol_34_no_47_english.pdf.