20.500.12556/RUL-185576 A Newcastle disease outbreak in backyard and free-range poultry in Slovenia Newcastle disease (ND) is a highly contagious and economically important viral disease of poultry, caused by virulent strains of Orthoavulavirus javaense (OAVJ). In Slovenia, vaccination is mandatory in commercial poultry and selected avian species, whereas backyard and free-range flock remain largely unregulated. In January and February 2025, two unrelated backyard and free-range flock of laying hens experienced acute outbreaks with severe clinical signs, increased mortality and distinct gross necropsy findings (haemorrhages in the mucosa of the gastrointestinal tract, multifocal pale foci in the liver, atrophy to enlarged hyperaemic spleen, oophoritis and salpingitis). OAVJ was detected in cloacal, oropharyngeal, and brain samples from both outbreaks using real-time RT-qPCR. Analysis of complete fusion (F) gene revealed identical nucleotide sequences in both outbreaks, with the cleavage site motif, characteristic of velogenic strains (amino acid sequence 112RRQKR116 at the C-terminus of the F2 protein and F at residue 117, the N-terminus of the F1 protein). Further phylogenetic analysis of the F gene demonstrated that both viruses belong to class II, sub-genotype VII.1.1, showing 99.6–100% identity with strains recently detected in Poland. The hemagglutinin-neuraminidase (HN) glycoprotein comprised 571 amino acids, consistent with genotype VII viruses, with several amino acid substitutions previously associated with functional relevance. These results highlight that, despite the absence of ND in Slovenia for more than three decades, local poultry populations remain highly susceptible to the introduction of the virus, especially in backyard flocks where monitoring and disease control are difficult to implement. Although a virulent virus was confirmed in both outbreaks, no further spread to other poultry holdings was detected. backyard poultry free-range poultry genotype VII.1.1 Newcastle disease Orthoavulavirus javaense Slovenia dvoriščna perutnina dvoriščna perutnina prostorejska perutnina genotip VII.1.1 atipična kokošja kuga Newcastleska bolezen Orthoavulavirus javaense Slovenija true false true Angleški jezik Slovenski jezik Članek v reviji 2026-08-11 04:01:33 2026-08-14 10:24:03 2026-08-15 04:01:46 0000-00-00 00:00:00 2026 0 0 8 str. Vol. 13 2026 0000-00-00 Zaloznikova Objavljeno apc 0000-00-00 0000-00-00 2026-01-01 616:579:636.5:579.62 2297-1769 10.3389/fvets.2026.1803248 280943363 Newcastle.pdf Newcastle.pdf 1 4A79E2AC2B8F06C4F8DC3BFF0DCF3673 b061e6df5b195576dbc032d319e72000bb602cd2acd5912f5324cb937fc2cdc7 d14026c1-97b8-11f1-9b0d-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=244369 https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2026.1803248/full 0 386efccc-97b9-11f1-9b0d-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=244372 Veterinarska fakulteta 0 0 0