Giardia duodenalis sub-Assemblage of animal and human origin in horses

In order to evaluate infection occurrence and the potential zoonotic role of horse isolates of Giardia 25 duodenalis, 431 individual fecal samples were genetically characterized by PCR tests –coupled sequencing 26 and phylogenetic analysis. Thirty-seven (8.6%) animals resulted infected by different Assemblage. The 27 presence of sub-Assemblage was assessed by characterizing the b-giardin gene for 16 of the 37 positive 28 horses. Ten isolates showed 99.6% to 100% homology with the sub-Assemblage described as B1–2 and 29 B1–6, three Assemblage A showed 99.8% homology with sub-Assemblage A1, while one Assemblage E 30 displayed 98.8% homology with sub-Assemblage E3. Furthermore, one isolate characterized as Assem- 31 blage A showed 99.6% homology with the sub-Assemblage B1–2 and one characterized as E was 100% 32 identical with sub-Assemblage B1–6. These results demonstrate the presence of both animal and human 33 sub-Assemblage of G. duodenalis in horses from Italy. Epidemiological and sanitary implications are 34 discussed.