Updated October 11, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Clostridium bacteria, mainly Clostridium perfringens and Clostridioides difficile, are commonly found in the intestines of healthy cats as well as sick ones. They can sometimes contribute to diarrhea, but a positive stool test alone doesn’t prove they’re the cause. Many cases improve with supportive care like a bland or high-fiber diet. Antibiotics are used only in specific situations. See your vet if diarrhea lasts more than a day or two or comes with blood, vomiting, or lethargy.
Signs
- Soft stool or diarrhea, often with mucus
- Straining and more frequent small stools (large-bowel diarrhea)
- Small amounts of fresh blood
- Gas or belly discomfort
- Vomiting or poor appetite in some cats
Why testing is tricky
Clostridium perfringens is often present in healthy cats, and many carry the genes for its toxins without being sick. Stool PCR panels frequently come back positive in cats with and without diarrhea. Specialist guidance says these results must be interpreted along with the cat’s signs and other tests, and a positive result alone shouldn’t lead to antibiotics.
Other causes vets consider
- Diet changes or food intolerance
- Parasites such as Giardia, Tritrichomonas, and worms
- Viral infections, including panleukopenia in unvaccinated kittens
- Inflammatory bowel disease or intestinal lymphoma in older cats
- Hyperthyroidism, pancreatic, or liver disease
- Stress
When to see a vet
Call your vet if diarrhea lasts more than 24–48 hours or keeps coming back. Go promptly if your cat has a lot of blood in the stool, is vomiting, stops eating, seems weak or lethargic, or is a kitten, senior, or has other health problems. Kittens can dehydrate quickly.
How vets diagnose it
Your vet will ask about diet and exposures, examine your cat, and usually check a stool sample for parasites. For ongoing diarrhea, bloodwork, a diet trial, imaging, or intestinal biopsies may follow.
Treatment
- Diet: a highly digestible gastrointestinal diet, or added fiber for large-bowel diarrhea.
- Probiotics: veterinary probiotics may help shorten diarrhea in some cats.
- Parasite treatment if any are found.
- Antibiotics are reserved for cats that are very ill, have signs of bacteria entering the bloodstream, or where other causes have been ruled out and Clostridium is strongly suspected.
- Fluids for dehydrated cats.
Supportive home care
- Keep fresh water available and encourage drinking. Wet food helps.
- Feed small, frequent meals of the diet your vet recommends.
- Make diet changes gradually over 7–10 days.
- Clean the litter box often and wash your hands after handling it.
- Keep your cat’s rear clean to prevent skin irritation.
What to avoid
- Human anti-diarrhea medications: Pepto-Bismol contains a salicylate that’s unsafe for cats, and loperamide (Imodium) can cause excitement or other problems in cats.
- Leftover antibiotics, which can make some diarrhea worse.
- Fasting for long periods: cats that don’t eat can develop fatty liver disease.
- Milk: most adult cats are lactose intolerant.
Frequently asked questions
Is Clostridium in cats contagious to people?
The risk appears low, but C. difficile can affect people. Wash your hands after cleaning litter, especially if someone in the home is elderly, pregnant, or has a weakened immune system.
Does canned pumpkin help?
A small amount of plain canned pumpkin adds fiber, but a vet-recommended fiber supplement or diet is more consistent. Ask your vet.
How long does Clostridium diarrhea last?
Mild cases often settle within a few days with supportive care. Ongoing diarrhea points to another underlying cause.
Sources
- Marks SL, et al. Enteropathogenic bacteria in dogs and cats: diagnosis, epidemiology, treatment, and control. J Vet Intern Med. 2011 (ACVIM consensus statement)
- Merck Veterinary Manual: Clostridial enterotoxicosis in small animals
- Cornell Feline Health Center: Diarrhea in cats
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.