Detection of pathogenic Leptospira in the environment and its association with antagonistic Pseudomonas spp. and rainy season

Abstract Typically, humans contract leptospirosis through exposure to soil or water contaminated with the urine of infected animals. Specifically, people working in inundated fields, engaged in aquatic sports, or exposed to contaminated floodwater after periods of heavy rainfall bear the risk of contracting leptospirosis. There is a critical gap in the knowledge of the environmental cycle, transmission, and interaction of Leptospira species with its environment. A few studies establish the presence of higher concentration of leptospires during the rainy season when compared to the dry season. Therefore, we assessed the abundance of leptospires during the dry and wet months and their interaction with other microbes. The overall detection rate of leptospires in paddy field for the test period was 52 (49.5%). Leptospiral concentration positively correlated with the amount of rainfall (mm) during the sampling when compared to months that received comparatively less rainfall (60% vs. 28.5%, respectively). When observed for the microbial interaction, Leptospira showed significant negative correlation with Pseudomonas and rainfall in the paddy field. Moreover, Pseudomonas negatively correlated with the amount of rainfall. Corroborative results of in-vitro studies suggest the antagonistic effect of Pseudomonas spp. on leptospires. The results indicate that seasonal changes influence the diversity of free-living well-adaptive aquatic antagonistic microbe populations and may in turn determine the survival of Leptospira in the environment. Thus, microbial interaction can be the possible enigma for the fluctuation of Leptospira count in rainy and dry seasons in environmental surface water, which needs to be further confirmed. This will pave way for a better understanding of the survival of leptospires and the seasonal trend of exposure to humans.