Molecular epidemiology of pathogenic Leptospira spp. in Thailand during 2024–2025, with detection of Leptospira weilii in human clinical specimens
- 1National Institute of Health of Thailand, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand
- 2Faculty of Medicine, Praboromarajchanok Institute, Ministry of Public Health, Nonthaburi, Thailand
Abstract
Background: Leptospirosis is a significant zoonotic disease in Thailand and globally. The causative agents are the spirochete bacteria in the genus Leptospira. An updated assessment of molecular epidemiology in Thailand is needed. Methodology/principal findings: Remnant EDTA blood specimens from suspected leptospirosis cases collected between June 2024 and July 2025 from the Central, Northern, Northeastern, and Southern regions of Thailand, were referred to the National Institute of Health. Demographic data were collected. Confirmed cases were diagnosed using TaqMan real-time PCR targeting LipL32 with a positively threshold of Ct < 37. Partial 16S rDNA (approximately 500 bp) was sequenced using Oxford Nanopore (Oxford, UK) and analyze by BLASTn. Among 1,063 suspected cases, 34 (3.2%) were real-time PCR confirmed. The majority of the cases were male (58.8%), primarily residing in Nan province (55.9%), and most positives were from specimens collected during the rainy season (76.5%). Twenty-six of 34 sequences (76.5%) clustered with L. interrogans, and 8 of 34 (23.5%) clustered with L. weilii within the primary pathogenic (P1) clade. Re-examination with published Thai and regional datasets showed broad circulation of L. interrogans and a Northern Thailand–Lao People Democratic Republic (PDR) focus for L. weilii To our knowledge, this is the first evidence of L. weilii detected in human clinical specimens in Thailand. Conclusion/significance: Pathogenic L. interrogans and L. weilii caused human Leptospirosis in Thailand during 2024–2025. These findings update the epidemiological status of Leptospira spp. in Thailand and can guide surveillance and control. Author summary: Leptospirosis is a zoonotic disease caused by pathogenic Leptospira spp., which is endemic in Thailand. Understanding the current molecular epidemiology of Leptospira spp. is important in public health intervention and disease control. In this study, we analyzed 1,063 suspected leptospirosis cases collected nationwide during 2024–2025. Thirty-four cases were confirmed by real-time PCR. The majority of cases were from Nan province, which is located in the Northern region of Thailand, and were collected during the rainy season (June – October). Genotypic analysis showed that 26 of 34 cases (76.5%) were infected with Leptospira interrogans, while 8 of 34 cases (23.5%) were infected with Leptospira weilii. L. interrogans and L. weilii are classified in primary pathogenic species that cause Leptospirosis. Specifically in Thailand, L. weilii has previously been identified in animal clinical specimens and environmental samples, but not in human clinical specimens. To our knowledge, this represents the first report of L. weilii detected in human clinical specimens in Thailand.
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BibTeX
@article{nukhonthod2026molecular,
title = {{Molecular epidemiology of pathogenic Leptospira spp. in Thailand during 2024–2025, with detection of Leptospira weilii in human clinical specimens}},
author = {Nattapon Nukhonthod and Ifwa Wirasit and Dararat Bangdee and Napaporn Sriden},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = sep,
doi = {10.1371/journal.pntd.0014720},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014720},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Molecular epidemiology of pathogenic Leptospira spp. in Thailand during 2024–2025, with detection of Leptospira weilii in human clinical specimens
AU - Nattapon Nukhonthod
AU - Ifwa Wirasit
AU - Dararat Bangdee
AU - Napaporn Sriden
PY - 2026
DA - 2026/09/15
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014720
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014720
AB - Background: Leptospirosis is a significant zoonotic disease in Thailand and globally. The causative agents are the spirochete bacteria in the genus Leptospira. An updated assessment of molecular epidemiology in Thailand is needed. Methodology/principal findings: Remnant EDTA blood specimens from suspected leptospirosis cases collected between June 2024 and July 2025 from the Central, Northern, Northeastern, and Southern regions of Thailand, were referred to the National Institute of Health. Demographic data were collected. Confirmed cases were diagnosed using TaqMan real-time PCR targeting LipL32 with a positively threshold of Ct < 37. Partial 16S rDNA (approximately 500 bp) was sequenced using Oxford Nanopore (Oxford, UK) and analyze by BLASTn. Among 1,063 suspected cases, 34 (3.2%) were real-time PCR confirmed. The majority of the cases were male (58.8%), primarily residing in Nan province (55.9%), and most positives were from specimens collected during the rainy season (76.5%). Twenty-six of 34 sequences (76.5%) clustered with L. interrogans, and 8 of 34 (23.5%) clustered with L. weilii within the primary pathogenic (P1) clade. Re-examination with published Thai and regional datasets showed broad circulation of L. interrogans and a Northern Thailand–Lao People Democratic Republic (PDR) focus for L. weilii To our knowledge, this is the first evidence of L. weilii detected in human clinical specimens in Thailand. Conclusion/significance: Pathogenic L. interrogans and L. weilii caused human Leptospirosis in Thailand during 2024–2025. These findings update the epidemiological status of Leptospira spp. in Thailand and can guide surveillance and control. Author summary: Leptospirosis is a zoonotic disease caused by pathogenic Leptospira spp., which is endemic in Thailand. Understanding the current molecular epidemiology of Leptospira spp. is important in public health intervention and disease control. In this study, we analyzed 1,063 suspected leptospirosis cases collected nationwide during 2024–2025. Thirty-four cases were confirmed by real-time PCR. The majority of cases were from Nan province, which is located in the Northern region of Thailand, and were collected during the rainy season (June – October). Genotypic analysis showed that 26 of 34 cases (76.5%) were infected with Leptospira interrogans, while 8 of 34 cases (23.5%) were infected with Leptospira weilii. L. interrogans and L. weilii are classified in primary pathogenic species that cause Leptospirosis. Specifically in Thailand, L. weilii has previously been identified in animal clinical specimens and environmental samples, but not in human clinical specimens. To our knowledge, this represents the first report of L. weilii detected in human clinical specimens in Thailand.
SN - 1935-2735
ER -