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

Abstract

Human alveolar echinococcosis (HAE), caused by the metacestode stage of Echinococcus multilocularis, 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 Echinococcus multilocuaris 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: 0.98/105, in 2022: 2.94/105/year; prevalence for 2019–2022: 4.91/105). 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.

Global and local drivers of Echinococcus multilocularis infection in the western Balkan region

“…Analysing the geographical distribution of infected and non-infected animals, we determined one significant high-rated cluster on the Drava Plain. This finding accords with previous studies, which suggest that the river and its catchment area provide appropriate circumstances for the parasite’s maintenance, in spite of the warm, albeit humid, climatic conditions, which considerably differ from the parasite’s environmental requirements 12 , 16 , 21 .…”

“…Despite the warming climate and the sub-Mediterranean or Mediterranean climatic conditions, an intensive spread can be seen in the wild canine population in the warmer regions of Europe 5 , 7 , 12 , 13 . This phenomenon also manifests in human alveolar echinococcosis cases 14 – 16 .…”

“…Echinococcus multilocularis is generally assumed to prefer cool and humid climates 11 , though its recent range extends to areas with warmer and drier climatic conditions 7 , 12 , 13 , 16 . In this study, we investigated the southwestern part of Hungary where the parasite forms a local endemic 7 .…”

The European Union One Health 2022 Zoonoses Report

“…In a few countries, the rise in case numbers over the last 5 years may be explained by increased human surveillance activities and improved notification systems for these diseases. Increased awareness about the diseases among clinicians, as well as immigration from endemic countries, may also have influenced the numbers of CE and AE diagnosed cases in some countries (Richter et al., 2019 )the recent discovery of AE in other countries such as Croatia and Serbia points to a geographical spread of the parasite (Balen Topić et al., 2023 ; Lalošević et al., 2023 ). It should be emphasised that the true prevalence of these diseases is extremely difficult to estimate due to the long incubation period, high proportion of asymptomatic or paucisymptomatic carriers who never seek medical attention, non‐specific symptoms and under‐reported or misdiagnosed CE and AE cases.…”

The One Health Concept

“…Foxes are the definitive hosts for the tapeworm Echinococcus multilocularis whose larval stage can infect humans within which they form potentially fatal alveolar hydatid cysts. The numbers of human infections with E. multilocularis have increased in several parts of Europe and one reason for this is undoubtedly the increase in the fox population [ 42 , 43 ].…”