biostudies-literatureUnknown29Kaufmann HGiardiosis is a worldwide intestinal parasitosis, affecting both humans and animals. Treatment in dogs remains limited and the lack of efficacy of the few approved medications is a rising concern. In this study, 23 dogs raised by veterinary students and naturally infected with Giardia duodenalis were treated in home conditions with fenbendazole (50 mg/kg orally for 5 consecutive days). Fecal samples were collected immediately before treatment (FS1), 2-4 days after treatment (FS2) and 8-10 days after treatment (FS3). Giardia duodenalis cyst excretion was measured quantitatively by direct immunofluorescence assay (DFA) at FS1, FS2 and FS3. Molecular typing with a nested PCR targeting the SSU _rDNA locus was also performed at FS1 and FS2. Fecal consistency improved in 16/21 dogs (76Parasite (Paris, France)49https://www.ebi.ac.uk/biostudies/studies/S-EPMC9621113biostudies-literatureLack of efficacy of fenbendazole against Giardia duodenalis in a naturally infected population of dogs in France.PMC9621113Kaufmann HPoirel MTZenner LBourgoin GBenabed SfalseLack of efficacy of fenbendazole against Giardia duodenalis in a naturally infected population of dogs in France.Giardiosis is a worldwide intestinal parasitosis, affecting both humans and animals. Treatment in dogs remains limited and the lack of efficacy of the few approved medications is a rising concern. In this study, 23 dogs raised by veterinary students and naturally infected with Giardia duodenalis were treated in home conditions with fenbendazole (50 mg/kg orally for 5 consecutive days). Fecal samples were collected immediately before treatment (FS1), 2-4 days after treatment (FS2) and 8-10 days after treatment (FS3). Giardia duodenalis cyst excretion was measured quantitatively by direct immunofluorescence assay (DFA) at FS1, FS2 and FS3. Molecular typing with a nested PCR targeting the SSU _rDNA locus was also performed at FS1 and FS2. Fecal consistency improved in 16/21 dogs (762022-01-01T00:00:00Z20222025-04-04T07:45:24.319Z2025-04-04T07:45:24.319ZS-EPMC96211133631510210.1051/parasite/2022048