Chronic diarrhea in horses demands a broader diagnostic lens
A new The Horse report highlights a key clinical distinction for equine practitioners: not every horse with watery manure has true chronic diarrhea. In coverage of a January 17-21, 2026 presentation at the Veterinary Meeting & Expo in Orlando, Amy Stewart, DVM, PhD, Dipl. ACVIM-LA, of North Carolina State University urged veterinarians to separate fecal water syndrome from chronic diarrhea caused by infectious, inflammatory, infiltrative, toxic, or management-related disease. The article outlines a stepwise workup that starts with history, physical exam, bloodwork, fecal egg counts, and Salmonella testing, then moves to imaging, abdominocentesis, and rectal mucosal biopsy when needed. It also points to common differentials including cyathostomes, Salmonella, Clostridium-associated disease, sand enteropathy, right dorsal colitis linked to NSAID exposure, and infiltrative or neoplastic bowel disease. (thehorse.com)
Why it matters: For equine veterinarians, the takeaway is practical: horses with chronic loose manure or fecal water may look relatively stable while still carrying treatable disease. That matters because definitive causes are often hard to confirm, fecal egg counts can miss encysted cyathostomes, and infectious causes may require repeated or pooled fecal testing. Recent AAEP guidance also reinforces that diarrheic horses, especially acute cases, warrant biosecurity precautions because enteric pathogens can spread by the fecal-oral route. Meanwhile, the evidence base around fecal water syndrome remains unsettled, with microbiome studies suggesting the condition is still poorly understood and investigational approaches such as fecal microbiota transplantation not yet clearly established. (thehorse.com)
What to watch: Expect continued interest in better diagnostics for occult parasitism, chronic Salmonella shedding, and microbiome-linked fecal water syndrome, along with more scrutiny of which horses truly benefit from diet changes, anti-inflammatory therapy, or microbiota-based interventions. (thehorse.com)