biostudies-literatureUtaaker KSNorwegian Environment Agency101004https://www.ebi.ac.uk/biostudies/studies/S-EPMC11513482biostudies-literatureUnknown25Wild and semi-domesticated reindeer graze freely on natural pastures in Norway, often sharing these with domestic sheep and other domestic and wild ruminants. In this study, faecal samples from wild reindeer and domestic sheep were collected from two areas in southern Norway and analysed to assess the occurrence and assemblage of <i>Giardia duodenalis.</i> Among 162 wild reindeer samples, 25 (15%) were positive for <i>Giardia</i>, showing high infection intensities, with most of the samples belonging to sub-assemblage AI, which has zoonotic potential. Interestingly, this study did not detect subassemblage AIII, known to be found in wild ruminants. Among 45 sheep samples, 13 (29%) were <i>Giardia-</i>positive, with most belonging to assemblage E. The finding of predominantly assemblage AI iInternational journal for parasitology. Parasites and wildlife<i>Giardia duodenalis</i> in sympatric wild reindeer and domestic sheep in Norway.PMC1151348220047048Utaaker KSRobertsen PAStrand OYtrehus BRobertson LJKifleyohannes Tfalse<i>Giardia duodenalis</i> in sympatric wild reindeer and domestic sheep in Norway.Wild and semi-domesticated reindeer graze freely on natural pastures in Norway, often sharing these with domestic sheep and other domestic and wild ruminants. In this study, faecal samples from wild reindeer and domestic sheep were collected from two areas in southern Norway and analysed to assess the occurrence and assemblage of <i>Giardia duodenalis.</i> Among 162 wild reindeer samples, 25 (15%) were positive for <i>Giardia</i>, showing high infection intensities, with most of the samples belonging to sub-assemblage AI, which has zoonotic potential. Interestingly, this study did not detect subassemblage AIII, known to be found in wild ruminants. Among 45 sheep samples, 13 (29%) were <i>Giardia-</i>positive, with most belonging to assemblage E. The finding of predominantly assemblage AI i2024-01-01T00:00:00Z2024 Dec2026-06-02T04:56:52.1Z2025-04-04T00:29:43.459ZS-EPMC115134823946913410.1016/j.ijppaw.2024.101004