Geospatial distribution of Leptospira-specific antibodies in febrile illness cases from Dakshina Kannada, India (2022-2023).

Abstract

Background: Leptospirosis, a significant zoonotic disease, remains a major public health challenge in Dakshina Kannada, Karnataka, India, particularly during the monsoon.

Objectives: To conduct spatial and temporal analysis of leptospirosis and investigate serogroup-specific distribution of Leptospira antibodies among febrile illness cases in Dakshina Kannada district, Karnataka state, India during 2022-2023.

Methods: A total of 3489 serum samples from human febrile illness cases were screened for Leptospira-specific IgM antibodies using commercial ELISA. A subset of 1631 samples underwent the Microscopic Agglutination Test (MAT) with a panel of 20 serovars representing 17 serogroups. Additionally, PCR targeting the lipL32 gene was performed on a subset of samples to identify active infections. Spatial mapping of seroprevalence and serogroup distribution was carried out using QGIS software.

Results: The overall seroprevalence was (657/3489) 19%. IgM ELISA detected antibodies in (593/3489) 17% of cases, while MAT confirmed a seroprevalence of (154/1631) 9%. Among 80 samples tested by LipL32 PCR, 13 (16%) were positive. Djasiman, Hurstbridge, Javanica, and Icterohaemorrhagiae were the most frequently detected serogroups. The highest positivity rates were observed in Moodabidri (29%) and Sulya (27%) Taluks. Fever was the most common symptom, and the 30-39 age group had the highest prevalence (23%, p < 0.05). Seasonal peaks corresponded with monsoon months.

Conclusion: This study highlights the need for integrated diagnostics, including ELISA, MAT, and early molecular detection through PCR, to improve leptospirosis management during peak seasons. The findings support targeted interventions, such as water sanitation and rodent control, to reduce the burden in this region. Expanded surveillance of livestock, wildlife, and the environment is crucial for understanding reservoirs and contamination sources.