Environmental determinants of leptospirosis: Integrating hydroclimatic and Ocean Health insights within a One Health framework

Background : Hydroclimatic events, such as intense rainfall and flooding, are known to amplify the transmission of the zoonotic disease leptospirosis on land. However, the fate of Leptospira once transported downstream into coastal ecosystems remains a critical knowledge gap. This review synthesizes the evidence for the land-sea continuum of leptospirosis risk under the One Health framework. Methods : A literature search of PubMed, Scopus, and SciELO (2014–2024) was conducted to identify terrestrial hydroclimatic drivers of leptospirosis in humans or animals. From 563 records, 196 articles were included for analysis. Results : Findings confirm that intense precipitation and flooding are the primary mechanisms for mobilizing Leptospira from terrestrial reservoirs, with 70% of studies identifying flooding as a definitive trigger. A key finding is the pathogen’s ability to survive in saline-affected coastal soils, suggesting a biological pathway into marine environments. While leptospirosis is a recognized cause of mortality in some marine mammals, the evidence highlights a complex “zoonotic cocktail” of serogroups/serovars – such as Pomona, Grippotyphosa, and Icterohaemorrhagiae – shared between terrestrial runoff and marine hosts. This underscores the potential for land-to-sea transmission, although endemic circulation within marine populations also plays a significant role. Conclusions : This review establishes the evidence for the hydroclimatic mobilization of Leptospira and proposes that this represents a significant, understudied threat to Ocean Health. We argue that a holistic One Health framework must bridge the land-sea divide. Integrating this continuum into surveillance – using tools such as integrated diagnostic protocols and shared databases – is a strategic imperative for addressing zoonotic challenges in a changing climate. One Health impact statement This review demonstrates that climate-driven flooding creates a direct hydrological and biological pathway for the “zoonotic cocktail” of Leptospira serogroups/serovars to contaminate coastal and marine ecosystems. This work provides actionable insights for public health officials, environmental managers, and marine conservationists by identifying a critical, underexplored risk at the land-sea interface. The added value of our One Health approach lies in integrating environmental triggers with multi-species epidemiological data, identifying a systemic threat – the potential for large-scale pathogen spillover into the marine food web – through integrated surveillance systems that monitor human, animal, and water-quality indicators in parallel. By bridging the conceptual gap between land and sea, this work offers a transdisciplinary framework for co-producing strategies with policy makers and local communities to assess and mitigate emerging zoonotic risks in a changing climate.