Temporal and spatial dynamics of canine leptospirosis in Croatia

Leptospirosis is a re-emerging zoonotic disease of increasing importance in both veterinary and public health, with its epidemiology strongly influenced by environmental and climatic factors. The aim of this study was to investigate the temporal and spatial distribution of canine leptospirosis in Croatia over an 11-year period (2013–2023), with particular emphasis on prevalence trends and serovar distribution. A total of 2,444 canine blood samples submitted for diagnostic testing were analysed using the microscopic agglutination test (MAT) for antibodies against 12 Leptospira serovars. Overall, 983 samples (40.22%) were seropositive. Annual prevalence showed marked fluctuations, with the highest numbers of positive samples recorded in 2018, 2020, and 2021. Geographical analysis revealed higher prevalence in central and northwestern Croatia, particularly in the City of Zagreb and surrounding counties. The most frequently detected serovars were Pomona (26.12%), Grippotyphosa (22.20%), Australis (16.96%), and Sejroe (14.95%), while other serovars occurred only sporadically. Temporal changes in serovar distribution were also observed, indicating dynamic epidemiological patterns. The identified fluctuations in prevalence are likely associated with environmental conditions favorable for Leptospira survival and transmission, including periods of increased precipitation and flooding documented in Croatia during the study period. These findings highlight considerable temporal, geographical, and serovar-related variability in canine leptospirosis, and emphasise the importance of continuous surveillance, regionally relevant vaccination strategies, and a One Health approach to disease prevention and control.