What Is Tritrichomonas?
Tritrichomonas (Tritrichomonas foetus, also named Tritrichomonas blagburni in cats) is a single-celled parasite that lives in a cat’s large intestine and causes chronic large-bowel diarrhea. It is most common in young cats under about two years old that came from crowded settings such as catteries, shelters, and multi-cat homes. Purebreds, including Bengals, Siamese, and Abyssinians, are diagnosed often, but any cat can be infected.
The parasite spreads through the fecal-oral route, mainly via shared litter boxes and close contact. Many infected cats otherwise seem healthy, with a normal appetite and energy, which can make the ongoing diarrhea puzzling for owners.
Why it matters
Tritrichomonas is frequently mistaken for Giardia and does not respond to the usual dewormers. The right test saves months of failed treatments.
Signs Owners Notice
- Soft, cow-pat-like stools with a strong smell that come and go for weeks or months
- Mucus or small amounts of fresh blood in the stool
- Straining, more frequent litter box trips, or accidents outside the box
- A red, sore, or swollen area around the anus
- Usually a normal appetite and body weight
Diagnosis
Your vet may look at a fresh fecal sample under the microscope, but this misses many infections. A fecal culture pouch designed for this parasite or, most accurately, a PCR test on a fresh stool sample is usually recommended. Avoid giving antibiotics before testing when possible, since they can temporarily mask the parasite. Other causes of cat diarrhea, including Giardia, coccidia, diet, and inflammatory bowel disease, are ruled out as needed.
Treatment and Outlook
- Ronidazole: the only drug shown to consistently clear the infection. It is used off-label, usually compounded, and requires careful dosing because it can cause neurological side effects such as wobbliness or tremors. Wear gloves when handling it.
- Diet: a highly digestible or higher-fiber diet can firm up stools.
- Gut support: your vet may suggest cat probiotics alongside treatment.
- Common dewormers and metronidazole: generally do not clear Tritrichomonas.
Without treatment, diarrhea often settles on its own over many months, sometimes up to two years, but cats may remain carriers that can infect housemates. With ronidazole most cats improve, though relapses happen and retesting is worthwhile.
Practical Tips for US Pet Owners
- Ask breeders or shelters about any history of chronic diarrhea before adopting a kitten.
- Scoop litter boxes at least daily and provide extra boxes in multi-cat homes.
- Keep a newly adopted kitten’s litter box separate until diarrhea is ruled out.
- Find a nearby practice through veterinary clinic listings.
When to see a vet
Book a visit if a young cat has soft or smelly stools for more than a week or two. Go sooner if there is vomiting, weight loss, lethargy, or a lot of blood.
Key Takeaways
- Tritrichomonas causes chronic, smelly large-bowel diarrhea in young cats from multi-cat settings.
- PCR testing on fresh stool is the most reliable way to diagnose it.
- Ronidazole is the main effective treatment and needs close vet supervision.
FAQ
Can dogs or people catch Tritrichomonas from my cat?
The cat form is not considered a meaningful risk to people, and dogs are rarely affected. Good hand hygiene after litter box cleaning is still wise.
Is it the same as Giardia?
No. Both are single-celled gut parasites, but Tritrichomonas needs different tests and different treatment.
Will it go away by itself?
Diarrhea often fades over months, but the cat may still carry and spread the parasite.