Tritrichomonas Infection Causes Diarrhea in Cats 🐱💩

By Dr Duncan Houston, BVSc

Tritrichomonas blagburni is a microscopic parasite that causes chronic diarrhea in cats—especially in kittens and cats housed in groups. In this 2025 veterinary guide, I explain how to recognize it, how to test for it, and what to know about the only effective treatment option. 🧪

🔬 What Is Tritrichomonas blagburni?

Often confused with Giardia, Tritrichomonas blagburni is a flagellated protozoan parasite that lives in the cat’s colon. The infection causes colitis, leading to persistent, foul-smelling, sometimes bloody or mucousy diarrhea. 🚨

Transmission:

• 🐾 Direct contact with infected feces
• 🚽 Shared litter boxes
• 🛋️ Grooming after stepping in contaminated areas

Organisms can survive in feces for up to 7 days at room temperature. 😬

🩺 Symptoms to Watch For

• 💩 Chronic, soft or runny diarrhea
• 🧪 Mucus or blood in stool
• 😼 No weight loss or behavior change (typically)
• 👃 Strong, unpleasant stool odor

Most cats remain otherwise bright and healthy—but the diarrhea often persists for months or even years. 🧻

🧬 How Is It Diagnosed?

Diagnosis requires special tests—not your standard fecal float. Your vet may use one of the following:

1. 💦 Direct Smear (14% sensitivity)

• Needs fresh rectal sample—not home litter box sample
• Quick and cheap but not reliable

2. 🧫 Culture Pouch Test (InPouch TF)

• Fecal sample added to pouch medium
• Incubated and checked microscopically for up to 12 days
• Inexpensive and accurate for many practices

3. 🧪 PCR Testing

• DNA test sent to a reference lab
• Most sensitive method—best for confirmation
• More expensive but most accurate

4. 🔬 Biopsy

• Only done if the cat is undergoing a biopsy anyway
• Must request special staining

Important: A negative test doesn’t rule out infection. Fresh samples and no recent antibiotics are key to accuracy. 🧼

💊 Treatment: Ronidazole

Ronidazole is the only known effective treatment. But it comes with precautions:

• 🧴 Must be compounded for cats (not commercially available)
• ⚠️ Wear gloves—ronidazole is carcinogenic
• 😾 Tastes bitter—use capsules, not liquid
• 🧠 Monitor for neurological side effects: ataxia, seizures, loss of appetite

Typically given once daily for 14 days. Probiotics and high-fiber diets may improve response. 💊

🧪 Post-Treatment Testing

It’s difficult to confirm complete eradication. Best practice includes:

• 🧬 PCR test 1–2 weeks after treatment
• 📆 Repeat at 20 weeks to check for recurrence

Cats should be isolated during treatment to avoid reinfection from housemates. 🏠

🕒 What If You Don’t Treat?

• 🔄 88% of infected cats resolve diarrhea naturally within 2 years
• 😷 They often remain contagious
• ⚠️ Symptoms can return with stress

In mild cases or small households, symptom monitoring may be enough. But testing is still encouraged to avoid spreading infection. 🧫

📱 Ask A Vet App Support

Worried about chronic diarrhea in your cat? The Ask A Vet app can help with:

• 💩 Differentiating between Giardia, Tritrichomonas, and IBD
• 📋 Ronidazole dosing and side effect monitoring
• 🧪 Submitting samples for PCR testing
• 🧻 Dietary support and probiotic suggestions

🏁 Final Takeaway

Tritrichomonas causes smelly, stubborn diarrhea in otherwise healthy cats. Accurate testing and cautious treatment are key. Whether you treat or monitor, knowing what you're dealing with helps you protect your cat—and your home—from this persistent parasite. 🐱💊💩