Endemicity, Clinical Features, Risk Factors, and the Potential for Severe Infection in Leptospira wolffii-Associated Leptospirosis in North-Central Bangladesh.

Leptospirosis is a zoonotic disease caused by pathogenic Leptospira, prevalent in tropical/sub-tropical regions. This study aimed to clarify the prevailing leptospiral species, clinical features, and risk factors of leptospirosis in north-central Bangladesh in 2024. Venous blood and urine samples were collected from 117 patients with clinically suspected leptospirosis. Among these cases, 75 (64%) tested positive for Leptospira infection by IgM ELISA test and/or PCR. By phylogenetic analysis of the 16S rRNA gene, all the samples tested were classified into L. wolffii (pathogenic group P2), showing high sequence identity to those of the type strain Khorat-H2 (97-99%) and L. wolffii reported in Bangladesh previously. Confirmed leptospirosis patients were mostly male (93%), aged 15-60 years (93%), living in rural areas in low socioeconomic conditions. Variable symptoms were presented by patients, with jaundice (84%), nausea/vomiting (84%), and myalgia (67%) being common. Some patients showed severe symptoms involving the nervous system (disorientation and neck stiffness) and the respiratory tract (cough, shortness of breath, and hemoptysis). Major risk factors for leptospirosis were exposures to mud/wet soil, sanding water, heavy rain, working in a paddy field, and cattle. In conclusion, L. wolffii was revealed to be circulating endemically in north-central Bangladesh, since its first detection in 2018, associated with variable and severe clinical symptoms in humans.