Safety profile and effects on the peripheral immune response of fecal microbiota transplantation in clinically healthy dogs

Abstract Background Fecal microbiota transplantation (FMT) is increasingly used for gastrointestinal and extra‐gastrointestinal diseases in veterinary medicine. However, its effects on immune responses and possible adverse events have not been systematically investigated. Hypothesis/Objectives Determine the short‐term safety profile and changes in the peripheral immune system after a single FMT administration in healthy dogs. Animals Ten client‐owned, clinically healthy dogs as FMT recipients, and 2 client‐owned clinically healthy dogs as FMT donors. Methods Prospective non‐randomized clinical trial. A single rectal enema of 5 g/kg was given to clinically healthy canine recipients. During the 28 days after FMT administration, owners self‐reported adverse events and fecal scores. On Days 0 (baseline), 1, 4, 10, and 28 after FMT, fecal and blood samples were collected. The canine fecal dysbiosis index (DI) was calculated using qPCR. Results No significant changes were found in the following variables: CBC, serum biochemistry, C‐reactive protein, serum cytokines (interleukins IL‐2, ‐6, ‐8, tumor necrosis factor TNF‐α), peripheral leukocytes (B cells, T cells, cluster of differentiation CD4+ T cells, CD8+ T cells, T regulatory cells), and the canine DI. Mild vomiting (n = 3), diarrhea (n = 4), decreased activity (n = 2), and inappetence (n = 1) were reported, and resolved without intervention. Conclusions and Clinical Importance Fecal microbiota transplantation did not significantly alter the evaluated variables and recipients experienced minimal adverse events associated with FMT administration. Fecal microbiota transplantation was not associated with serious adverse events, changes in peripheral immunologic variables, or the canine DI in the short‐term.