A geospatial study led by researchers at the University of Sydney found 79 canine leptospirosis cases and 281 human cases reported (190 analyzed) across New South Wales, concluding that the two sets of cases follow distinct transmission pathways with limited evidence of dog-to-human spread.

The study, published on 23-Sep-2025 (online ahead of print), mapped infections across regions including Greater Sydney, the South Coast and the North Coast and compared the serovars affecting each species. Its findings underscore separate patterns of exposure for people and dogs rather than a single, shared source of infection.

Researchers Christine Griebsch, Jacqueline Norris and Michael P. Ward of the University of Sydney conducted the geospatial analysis, which examined the locations and serovar profiles of cases. Bowen Li of the Shanghai Jiao Tong University Journal Center is listed as the media contact for the publication.

The team reported that canine infections were predominantly caused by serovar Australis and Copenhageni, with common symptoms in dogs such as vomiting, diarrhea, and lethargy. Those dog cases tended to cluster in urban environments where contamination from rat urine was observed in the study’s spatial data.

By contrast, human cases in the study were concentrated in agricultural settings linked to mouse plagues, reflecting different environmental drivers for infection in people. General symptoms of leptospirosis in humans include fever, chills, and muscle pain, highlighting the significant health impacts associated with the disease. The researchers found no spatial correlation between the human and canine case distributions at the scales analysed, a result that informed their conclusion of limited evidence for dog-to-human transmission.

The analysis covered locations across New South Wales and identified clear geographic separation in hotspots for each species. Canine clustering appeared in and around Greater Sydney and the South Coast, while human infections were more often centred on the North Coast.

Beyond mapping, the study compared serovar distributions: dogs were mainly affected by Australis and Copenhageni, whereas the human serovar profile in the broader dataset differed, supporting the spatial findings that the two epidemics are driven by distinct exposures.

Authors framed the results around the implications of different environmental reservoirs. In urban areas, the spatial pattern for dogs aligned with sites likely contaminated by rats, while in rural and agricultural zones, the human pattern aligned with mouse activity identified in the study’s contextual data. This aligns with the One Health approach, which integrates human, animal, and environmental health to prevent diseases.

Public reporting of regional canine infections has noted local impacts on the South Coast, where earlier accounts drew attention to rising cases; the South Coast reference here aligns with coverage available in regional outlets such as Region.

The University of Sydney led the research effort and compiled the geospatial dataset used to compare cases across New South Wales. The study’s publication date is 23-Sep-2025 (online ahead of print), and the paper lists Bowen Li of the Shanghai Jiao Tong University Journal Center as the media contact for press enquiries.

Where infections overlap geographically, the authors reported only limited evidence of shared sources at the spatial resolution they analysed, indicating that interventions may need to be tailored to the species and setting involved rather than assuming a single common source of transmission. Pet owners can reduce the risk of leptospirosis in dogs primarily by vaccinating annually with a leptospirosis vaccine and limiting access to standing or natural water sources.

As of the paper’s publication, the dataset included the 79 canine records and approximately 300 human records analysed for spatial and serovar patterns. The study’s geographic breakdown highlighted urban rat-associated contamination for dogs and agricultural mouse-associated clusters for people, conclusions the authors drew from the mapped distributions and serovar differences.

Source

Original reporting: view the original article.