Fecal microbiota transplantation shows promise in slowing or reducing cognitive impairment in aging dogs

OBJECTIVE: To investigate potential effects of fecal microbiota transplantation (FMT) on cognitive scores and bacterial microbiota composition in dogs with suspected canine cognitive dysfunction (CCD). METHODS: The study was conducted from September 19, 2024, to September 11, 2025. Dogs with presumptive CCD were given oral FMT capsules daily for 90 days. Each dog received 1 FMT capsule every 12 hours. Fecal samples and cognitive (disorientation, impaired social interactions, sleep disturbance, house soiling, learning and memory loss, activity changes, and anxiety and fear [DISHAA]) assessments were completed at baseline and on days 30, 60, and 90. Fecal samples were submitted for 16S rRNA gene sequencing. RESULTS: 11 dogs were enrolled; 10 dogs had no adverse events from FMT treatment, and 1 dog developed gastrointestinal signs and was removed from the study. All 10 remaining dogs had complete microbiome data; however, owners of 4 dogs did not report final (90-day) DISHAA scores. Of the 6 dogs with complete data, cognition improved in 4 (mean, -8.25 points) but worsened in 2 (mean, +7 points) according to owner-reported DISHAA scores. Microbiome richness and diversity increased in 4 of the 6 dogs. Several dogs also showed positive modulation of microbiome composition including reductions in Streptococcus spp and increases in Peptacetobacter hiranonis, Prevotella copri, and Bacteroides spp. CONCLUSIONS: These findings provided preliminary evidence that FMT may help improve cognitive function in dogs with CCD. However, the study sample size was small and ideal FMT dosing level and treatment duration remain undefined. A larger study with longer follow-up is warranted, based on our results. CLINICAL RELEVANCE: FMT showed promise in slowing or reducing cognitive impairment in aging dogs and may be considered as adjunct therapy in these cases.