This study presents the current status of human leptospirosis in Croatia from an epidemiological and clinical viewpoint. Data from annual reports of the Croatian Institute for Public Health as well as archives of the University Hospital for Infectious Diseases 'Dr Fran Mihaljevic' (UHID) in Zagreb were used in this retrospective cohort analysis. The mean yearly incidence of leptospirosis from 1990 to 2007 was 1.83/100 000 inhabitants, with an incidence >2.5/100 000 inhabitants recorded approximately every 3-4 years, making Croatia one of the countries with the highest incidence of human leptospirosis in Europe. In addition to the majority of sporadic cases, two minor outbreaks were recorded. The clinical burden and more detailed epidemiology of 130 patients hospitalised at UHID in the period 1997-2007 were also studied. Clinical presentations were as expected, with an overall case fatality rate (CFR) of 0.77%. The most commonly established infective serovars were Australis followed by Saxkoebing and Grippotyphosa. In comparison with previous periods, the mean yearly number of patients with leptospirosis hospitalised at UHID decreased, but among them a rather higher rate of patients with Weil's disease and a higher CFR was observed.

Leptospirosis is one of the most common zoonotic infections and a major problem in terms of both veterinary medicine and public health. However, the disease is under-recognised and under-diagnosed worldwide, particularly in horses. Clinical leptospirosis in horses is mainly associated with recurrent uveitis (ERU), which has recently been studied more intensively, and reproductive disorders, the epidemiology of which is still relatively poorly understood. To enhance our comprehension of abortions caused by leptospirosis in horses and to identify the causative strains, a serological study was carried out with subsequent molecular characterisation of the isolate obtained. Using the microscopic agglutination test (MAT), serum samples from mares that aborted and foetal fluids (when available) were tested for antibodies against Leptospira spp. Furthermore, bacteria isolation from kidney cultures was conducted. Of 97 mare serum samples, 21 (21.64%) tested positive, with Grippotyphosa and Pomona being the most frequently detected serogroups. A significantly higher seroprevalence was found in aborting mares compared to the healthy horse population from the same geographical area, as well as a pronounced seasonal variation. Leptospiral antibodies were not detected in any of the foetal fluids, but isolation was successful in 1 case out of 39 (2.56%). Genotyping by multilocus sequence typing (MLST) and core genome multilocus sequence typing (cgMLST) identified the obtained isolate as Leptospira kirschneri, serogroup Pomona, serovar Mozdok. Further surveillance and molecular typing of Leptospira strains causing abortion in horses would be invaluable in understanding the prevalence and impact of leptospirosis on equine reproductive health in Europe.

Wild animals often serve as reservoirs for vector-borne zoonoses, which are on the rise worldwide but have not yet been sufficiently researched. Vector-borne zoonoses, such as those caused by Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, and Dirofilaria immitis, are a growing public health concern due to their increasing incidence and broad host range. The aim of this study was to determine the prevalence and risk factors for vector-borne bacterial (borreliosis, anaplasmosis, ehrlichiosis) and parasitic (dirofilariasis) pathogens and to detect some of these pathogens in the red fox (Vulpes vulpes) population in Croatia. A total of 179 blood samples from foxes from nine districts were analysed. The SNAP ^® 4Dx ^® Plus rapid test was used to detect circulating D. immitis antigen and antibodies against B. burgdorferi, A. phagocytophilum/Anaplasma platys, and Ehrlichia canis/Ehrlichia ewingii. Circulating D. immitis antigen was detected in 6.70% of the samples (95% CI: 3.20–10.19%), while antibodies against A. phagocytophilum/A. platys were found in 10.06% (95% CI: 5.8–14.25%). Only one sample was positive for B. burgdorferi, while no antibodies were detected for E. canis/E. ewingii. Spatial analysis revealed statistically significant differences in prevalence by geographical region (district) and age, while no significant correlations were found. In the standard PCR analysis, DNA of D. immitis was not detected in any of the eight positive and eight negative SNAP ^® 4Dx ^® Plus samples. D. repens, A. reconditum, or co-infections were also not detected by PCR. Of the nine samples that tested positive for A. phagocytophilum/A. platys antibodies, four were confirmed to be positive for A. phagocytophilum by nested and semi-nested PCR targeting the 16S rRNA and GroEL genes. Phylogenetic analysis revealed similarities with various European strains, including zoonotic strains. This study is the first molecular detection of A. phagocytophilum from blood samples of red foxes in Croatia. The results show that red foxes are not free from infections such as anaplasmosis and dirofilariasis, emphasising their possible role in the maintenance and transmission of these pathogens in certain regions of Croatia. These results underline the need for further research to better understand the epidemiological importance of red foxes in the spread of vector-borne diseases.