Occurrence and molecular characterization of Giardia duodenalis in domestic and wild mesocarnivores in Bosnia and Herzegovina

<i>Giardia duodenalis</i> is a protozoan parasite with worldwide distribution and recognized zoonotic potential. Data on its molecular epidemiology in Bosnia and Herzegovina (BiH) are scarce, particularly in wild mesocarnivores. This study aimed to investigate the occurrence and genetic characterization of <i>G. duodenalis</i> in domestic and wild mesocarnivores across BiH. A total of 520 fecal samples were collected between 2023 and 2025, including dogs (<i>Canis lupus familiaris</i>, n = 433), cats (<i>Felis catus</i>, n = 21), red foxes (<i>Vulpes vulpes</i>, n = 39), golden jackals (<i>Canis aureus</i>, n = 17), European pine martens (<i>Martes martes</i>, n = 5), grey wolves (<i>Canis lupus</i>, n = 1), European badgers (<i>Meles meles</i>, n = 2), and European wildcats (<i>Felis silvestris</i>, n = 1). Screening was performed using fecal flotation and immunofluorescence assay (IFAT), with selected samples further analyzed by high-resolution melting (HRM) real-time PCR (qPCR-HRM) and targeted next-generation sequencing (NGS). Overall, <i>G. duodenalis</i> was detected in 20.96 % (109/520) of samples by flotation and IFAT. Cats showed the highest positivity rate (71.43 %), followed by dogs (21.02 %), whereas wild mesocarnivores exhibited substantially lower detection rates (5.13 % in red foxes and 5.88 % in golden jackals). Among dog subpopulations, hunting dogs showed the highest positivity (49.52 %) compared with shelter dogs (6.72 %). Molecular typing revealed assemblage D as predominant (65.91 %), followed by assemblages B (18.18 %), C (6.82 %), and F (4.55 %), with occasional mixed profiles. Assemblage D occurred across multiple hosts, while the zoonotic assemblage B was detected exclusively in wild canids. This study provides the first molecular epidemiological evidence of <i>G. duodenalis</i> assemblage circulation among domestic and wild mesocarnivores in Bosnia and Herzegovina. The findings identify cats and hunting dogs as key hosts contributing to parasite circulation and demonstrate limited but epidemiologically meaningful involvement of wild mesocarnivores, underscoring the importance of integrated One Health surveillance to assess transmission risks at the domestic-wildlife-human interface.