Liver fluke infections are recognised as diseases with worldwide distribution and considerable veterinary and public health importance. The giant liver fluke, Fascioloides magna, is an important non-native parasite which has been introduced to Europe, posing a threat to the survival of local wildlife populations such as red deer (Cervus elaphus). The aim of the study was to analyse differences in liver proteomes between F. magna-infected and control red deer groups using a label-based high-throughput quantitative proteomics approach. The proteomics analysis identified 234 proteins with differential abundance between the control and infected groups. Our findings showed that F. magna infection in this definitive host is associated with changes in the metabolism of proteins and fatty acids, oxidative stress, fibrosis, and signaling pathways. The identified proteins and associated biological pathways represent a valuable contribution to the understanding of host–parasite interactions and the pathogenesis of liver fluke infection.

Fascioloidosis is a parasitic disease caused by a trematode Fascioloides magna. Since major histocompatibility complex (MHC) genes play an important role in the immune response, the aim of this study was to compare the potential differences in MHC class II SLA-DRB1 exon 2 genes between wild boar populations from infected (cases) and non-infected areas (controls). During the winter of 2021, a total of 136 wild boar tissue samples were collected, 39 cases and 97 controls. DNA was extracted and sequenced using the Illumina platform. Differences in distributions of allele combinations were calculated using the Chi-Square test for homogeneity and between proportions using the large-sample test and Fisher–Irwin test. Analysis revealed 19 previously described swine leucocyte antigen (SLA) alleles. The number of polymorphic sites was 79 (29.6%), with 99 mutations in total. Nucleotide diversity π was estimated at 0.11. Proportions of the alleles SLA-DRB1*12:05 (p = 0.0008379) and SLA-DRB1*0101 (p = 0.0002825) were statistically significantly higher in controls, and proportions of the SLA-DRB1*0602 (p = 0.006059) and SLA-DRB1*0901 (p = 0.0006601) in cases. Alleles SLA-DRB1*04:09, SLA-DRB1*0501, SLA-DRB1*11:09, and SLA-DRB1*1301 were detected only in cases, while SLA-DRB1*0404, SLA-DRB1*0701, SLA-DRB1*02:10, and SLA-DRB1*04:08 were present only in controls. We did not confirm the existence of specific alleles that could be linked to F. magna infection. Detected high variability of the MHC class II SLA-DRB1 exon 2 genes indicate high resistance potential against various pathogens.

Liver fluke infections are acknowledged as diseases with global prevalence and significant implications for both veterinary and public health. The large American liver fluke, Fascioloides magna, is a significant non-native parasite introduced to Europe, threatening the survival of local wildlife populations. The aim of this study was to analyze differences in the serum proteome and metabolome between F. magna-infected and control red deer. Serum samples from red deer were collected immediately following regular hunting operations, including 10 samples with confirmed F. magna infection and 10 samples from healthy red deer. A proteomics analysis of the serum samples was performed using a tandem mass tag (TMT)-based quantitative approach, and a metabolomics analysis of the serum was performed using an untargeted mass spectrometry-based metabolomics approach. A knowledge-driven approach was applied to integrate omics data. Our findings demonstrated that infection with liver fluke was associated with changes in amino acid metabolism, energy metabolism, lipid metabolism, inflammatory host response, and related biochemical pathways. This study offers a comprehensive overview of the serum proteome and metabolome in response to F. magna infection in red deer, unveiling new potential targets for future research. The identification of proteins, metabolites, and related biological pathways enhances our understanding of host–parasite interactions and may improve current tools for more effective liver fluke control.

The trematode Fascioloides magna is originally a parasite of North American deer species. Upon its arrival to Europe, F. magna met new intermediate and final hosts. Depending on the type of host, the clinical picture, pathological findings, epidemiology and outcome can vary significantly. As an aberrant host, it was long believed that the roe deer (Capreolus capreolus) fails to develop pseudocysts, and therefore the infected animal dies before the parasite can mature and start to produce eggs. In this study, 676 roe deer livers were collected in Croatia during the hunting years of four consecutive years (2019–2023) in Bjelovar-Bilogora County (BB), and 184 livers were collected from Zagreb County (ZG) in the hunting year 2022/2023. Livers were analysed macroscopically and on a cut surface for lesions and any developmental stage of F. magna according to a standard protocol. The mean prevalence of infected livers during the whole study period was 12.86% in BB and 3.8% in ZG. No pseudocysts were detected in samples from ZG, while there was an increasing trend of pseudocyst presence over time in BB. The occurrence of pseudocysts in infected livers showed a rapid increase after the hunting season 2019/2020, before becoming constant (at approx. 40%). The odds of finding pseudocysts ranged between 2.7 (OR = 2.7317, CI 95% 0.3108 to 24.0095, p = 0.365) and 2.9 (OR = 2.9167, CI 95% 0.3163 to 26.8924, p = 0.345) times higher in later years compared to 2019/2020. Similarly, an increasing trend (though less pronounced) was observed in the numbers of livers simultaneously containing pseudocysts and fluke migratory stages. The results indicate a potential change in the roe deer–F. magna association, where an increasing number of roe deer are forming pseudocysts and can survive even multiple infections.

Protoparvoviruses are highly contagious pathogens that cause severe, often fatal diseases in both domestic and wild carnivores. Golden jackal (Canis aureus) populations have experienced expansion in recent years, increasingly occupying urban and peri-urban areas. Despite this, they remain largely overlooked in scientific research. This study aimed to detect and characterise Protoparvovirus carnivoran1 circulating in a golden jackal population in Croatia and to assess their role in the epidemiology of parvovirus infections in companion animals. Small intestines from 55 jackals hunted in 2024 and 2025 were tested for Protoparvovirus carnivoran1 using real-time PCR. Positive samples were found across all sampling sites, with an overall positivity rate of 40%. Based on characteristic amino acid residues within the VP2 protein, the viruses detected in jackals were classified as feline panleukopenia virus (FPV). Phylogenetic analysis of the VP2 protein demonstrated considerable genetic diversity among strains circulating in Croatia. Additionally, a distinct group was identified, shared exclusively by Croatian domestic cats and golden jackals. Amino acid analysis revealed the novel A91T mutation, found only in jackals, and the E411Q mutation, unique to Croatian FPV strains. Structural modelling of the VP2 protein indicates that the observed mutations are located on the protein surface, within the antibody-binding site. These findings highlight the potential role of wild carnivores in parvovirus epidemiology and underscore the importance of including them in future surveillance and research efforts.

Summary: In Europe, red deer and fallow deer are the defi nitive hosts for the non-native fl uke Fascioloides magna . Upon entering the host, a juvenile fl uke emerges from the metacercariae and travels through the abdominal cavity in search of the liver. The aim of this study was to determine the distribution of F. magna pseudocysts in the livers of red deer and fallow deer, and to investigate whether this distribution varies within the livers according to host species and the severity of infection. In this study, 143 red deer livers and 178 fallow deer livers were collected. Livers were divided into three sections (observed from the diaphragm side): left containing the lobus hepatis sinister, middle containing the lobus caudatus and lobus quadratus, and right one containing the lobus hepatis dexter. Sections were sliced to a 2 cm thickness and analysed. A signifi cantly higher number of pseudocysts was found in the middle section of the liver compared to the left or right sections, while no differences were found between the left and right sections. The odds ratio indicates a 7 times (red deer) and 3.7 times (fallow deer) higher probability of pseudocysts being present in the middle section compared to the left section, or 10 and 3.8 times, respectively, compared to the right section. Red deer livers generally harboured more pseudocysts than fallow deer livers in all sections. Both species exhibited a similar pattern of pseudocyst distribution in the liver, with the middle section appearing to be the most suitable site for pseudocyst localization due to the abundance of blood vessels and bile duct terminations. No relationship was found between the severity of infection and pseudocyst distribution.