Adverse events after fecal microbiota transplantation in nine cats: a case series

This case series describes nine cases of fecal microbiota transplantation in cats and associated adverse events (AEs) from two tertiary referral hospitals. AEs were graded according to criteria established by the Veterinary Cooperative Oncology Group's Common Terminology Criteria for Adverse Events (VCOG-CTCAE v2) for clinical trials. Cats received 5-6 g/kg donor feces 2-6 times for chronic enteropathy (n = 4) or therapy-resistant diarrhea (n = 5). AEs included lethargy (n = 7), vomiting (n = 5), diarrhea (n = 5), weight loss (n = 5), inappetence (n = 5), dehydration (n = 5), abdominal pain (n = 2), gastroenterocolitis based on ultrasound (n = 2) and anorexia (n = 1). Temperatures of up to 103.4°F were noted but did not meet the criteria for AEs (>103.5°F). Cats responded to antimicrobials (metronidazole, marbofloxacin), anthelmintics (fenbendazole), supportive care with fluids, ondansetron and mirtazapine (n = 5), gabapentin (n = 2), pradofloxacin (n = 1) or self-resolved (n = 1). Positive response to fecal microbiota transplantation for the presenting complaint was seen in eight cats (seven complete, one partial and transient).Relevance and novel informationFecal microbiota transplantation is increasing in usage among companion animals. Fecal microbiota transplantations in cats have been rarely described in the literature as have AEs after administration. This case series represents the first description of AEs after fecal microbiota transplantation in cats.