Emergence of in Central Continental Croatia: A Human Case Series and Update on Prevalence in Foxes

Human alveolar echinococcosis (HAE), caused by the metacestode stage of , has emerged in many European countries over the last two decades. Here, we report the first data on the new HAE focus with increasing incidence in central Croatia, describe its clinical presentation and outcomes in diagnosed patients, and provide an update on the prevalence and geographic distribution of in red foxes. After the initial case in 2017 from the eastern state border, from 2019 to 2022, five new autochthonous HAE cases were diagnosed, all concentrated in the Bjelovar-Bilogora County (the county incidence in 2019 and 2021: 0.98/10, in 2022: 2.94/10/year; prevalence for 2019-2022: 4.91/10). The age range among four female and two male patients was 37-67 years. The patients' liver lesions varied in size from 3.1 to 15.5 cm (classification range: P2N0M0-P4N1M0), and one patient had dissemination to the lungs. While there were no fatalities, postoperative complications in one patient resulted in liver transplantation. In 2018, the overall prevalence of red foxes was 11.24% (28/249). A new focus on HAE has emerged in central continental Croatia, with the highest regional incidence in Europe. Screening projects among residents and the implementation of veterinary preventive measures following the One Health approach are warranted.