While mitogenome mutations leading to pathological manifestations are rare, more than 200 such mutations have been described in humans. In contrast, pathogenic mitogenome mutations are rare in domestic animals and have not been described at all in cattle. In the small local Slovenian cattle breed Cika, we identified (next-generation sequencing) two cows with the T10432C mitogenome mutation in the ND4L gene, which corresponds to the human T10663C mutation known to cause Leber’s hereditary optic neuropathy (LHON). Pedigree analysis revealed that the cows in which the mutation was identified belong to two different maternal lineages with 217 individual cows born between 1997 and 2020. The identified mutation and its maternal inheritance were confirmed by Sanger sequencing across multiple generations, whereas no single analysis revealed evidence of heteroplasmy. A closer clinical examination of one cow with the T10432C mutation revealed exophthalmos, whereas histopathological examination revealed retinal ablations, subretinal oedema, and haemorrhage. The results of these analyses confirm the presence of mitochondrial mutation T10432C with homoplasmic maternal inheritance as well as clinical and histopathological signs similar to LHON in humans. Live animals with the mutation could be used as a suitable animal model that can improve our understanding of the pathogenesis of LHON and other mitochondriopathies.

In a total of 1536 blood serum samples analysed by ELISA, antibodies for IAV nucleoprotein (NP) were detected in 30.3%. Results from HI show that the most common subtype of swIAV in the Croatian pig population was H1N1 (44.6%), followed by H3N2 (42.7%) and H1N2 (26.3%). Antibodies to at least one subtype were detected in 62.19% of blood serum samples. Detection of swIAV antigen was performed by IHC and detected in 8 of 28 lung samples collected post-mortem. The matrix (M) gene was detected in nine of one hundred and forty-two lung tissue samples and in seven of twenty-nine nasopharyngeal swabs. Phylogenetic analysis of amplified HA and NA gene fragments in Croatian isolates suggests the presence of swIAV H1avN1av.

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.

Bornaviruses are neurotropic, negative-sense RNA viruses with zoonotic potential, notably Borna disease virus 1 (BoDV-1) and variegated squirrel bornavirus 1 (VSBV-1). BoDV-1 is endemic in certain regions of Central Europe and maintained in bicolored white-toothed shrews, but its presence in Croatia has not been investigated. Given Croatia’s diverse biogeography and the prevalence of rodent-borne diseases, this study aimed to investigate the presence of orthobornaviruses in wild canids and mustelids. Brain samples from red foxes (Vulpes vulpes), golden jackals (Canis aureus moreoticus), wolves (Canis lupus), martens (Martes martes) and badgers (Meles meles) were analysed using pan-bornavirus RT-PCR. Despite successful RNA extraction and internal control amplification, bornavirus RNA was not detected in any of the 860 animal samples tested. Although no orthobornavirus RNA was detected, the results still provide valuable information: bornavirus infections appear to be absent or extremely rare in Croatian wild canids and mustelids. By excluding these species as current potential reservoir hosts, this study helps to refine the geographical extent of bornavirus endemicity and emphasises the importance of continuous One Health surveillance in regions with favourable ecological conditions for zoonotic spillover.

Porcine reproductive and respiratory syndrome virus (PRRSV) is among the most economically damaging swine pathogens worldwide, yet its evolutionary origins and the forces driving its diversification remain unclear. Using complete arterivirus genomes, we applied an integrative, high-resolution phylogenomic framework that combined time-calibrated evolutionary inference with recombination- and introgression-aware analyses. This approach resolved the divergence history of PRRSV and uncovered a cryptic mosaic genome and reticulation shaped by recurrent recombination and interspecies viral gene flow. We show that North American and European lineages diverged in the late 19th century – long before the emergence of disease on either continent and that their closest relatives are rodent arteriviruses, indicating a rodent ancestry. Genome-wide scans further reveal that PRRSV evolution is driven by adaptive changes in the glycoprotein ORF3, whereas the replicase genes remain a conserved genomic backbone. Demographic reconstructions suggest that the intensification of pig farming in the mid-20th century-imposed transmission bottlenecks that amplified genetic drift and accelerated the fixation of advantageous variants. Together, these findings rewrite the evolutionary timeline of PRRSV and provide a framework for understanding how human practices shape the emergence and spread of viral pathogens across animal and human health.

Yersinia pseudotuberculosis caused a fulminant outbreak in a Croatian breeding colony of 84 guinea pigs, in which 80 animals (95%) died within 72 hours after abrupt food refusal and marked lethargy, without diarrhoea. Seven freshly dead animals were examined. At necropsy, 2–5 mm, white-yellow nodules were found distributed in the liver, spleen, lungs, mesenteric lymph nodes and partly also in the small intestine. Aerobic culture of these organs on Columbia blood agar (28°C, 24–48 h) revealed pure growth of Y. pseudotuberculosis. Histology showed well demarcated necro-pyogranulomatous lesions with central bacterial colonies, margins of neutrophils and a peripheral coat of macrophages and few lymphocytes. Immunohistochemistry confirmed abundant lysozyme-positive macrophages and few CD3-positive T and CD79α-positive B cells, indicating a predominantly innate response. This case report emphasises the extreme lethality and rapid progression of guinea pig yersiniosis and highlights its zoonotic potential.