Ollulanus tricuspis in Cats: A Vet’s 2025 Guide to Persistent Vomiting, Diagnosis & Treatment 🐱

👋 Hi, I’m Dr. Duncan Houston BVSc, veterinarian and founder of Ask A Vet. Chronic vomiting is common in cats—but when hairballs aren’t the culprit, one rare parasite to consider is Ollulanus tricuspis, the “stomach worm.” Though often overlooked, this tiny nematode can cause persistent vomiting, anorexia, and gastritis. In our 2025 guide, we’ll cover the science, diagnostics, treatment options, and home-care protocols to help your cat find relief.

📘 1. What Is Ollulanus tricuspis?

O. tricuspis is a minute, ovoviviparous (larviparous) nematode—typically ≤ 1 mm long—that colonizes the gastric mucosa of cats and other felids around the globe :contentReference[oaicite:3]{index=3}. Adult females produce live third-stage larvae directly inside the stomach, often causing low-grade inflammation and mucus production :contentReference[oaicite:4]{index=4}.

🌍 2. Prevalence & Risk Factors

While usually uncommon in single-pet households, prevalence can range up to 27–38% in multi-cat environments or strays :contentReference[oaicite:5]{index=5}. Risk factors include:

• Living in catteries or high-density colonies.
• Free-roaming or outdoor/hunting behavior.
• Sharing vomitus in multi-cat environments.

⚠️ 3. Why It Warrants Attention

• Causes chronic vomiting—often immediately after meals—distinct from hairballs :contentReference[oaicite:6]{index=6}.
• Can lead to weight loss, decreased appetite, and persistent gastritis :contentReference[oaicite:7]{index=7}.
• May contribute to gastric fibrosis or rare carcinogenesis in heavily infected cases :contentReference[oaicite:8]{index=8}.

🔍 4. Clinical Signs

Signs are often subtle or intermittent:

• Vomiting shortly after eating (not hairball-related).
• Poor appetite, dehydration, and lethargy.
• Weight loss or ongoing mild gastritis.
• Occasional diarrhea or mucus.

🧭 5. Diagnostic Strategies

1. History & Physical: note timing of vomit and household environment.
2. Vomitus examination: induction with xylazine or gastric lavage can recover larvae from ~70% of infected cats :contentReference[oaicite:9]{index=9}.
3. Baermann technique: separates live larvae from vomiting material—recommended for fresh samples :contentReference[oaicite:10]{index=10}.
4. Endoscopic biopsy: useful when lavage samples are inconclusive :contentReference[oaicite:11]{index=11}.
5. Histopathology (post-mortem): mucosal thickening, lymphoid aggregates :contentReference[oaicite:12]{index=12}.

🛠️ 6. Effective Treatment Protocols

While no drugs are officially labelled for this use, evidence supports several efficacious options:

• Fenbendazole 20–50 mg/kg PO for 3–5 days is most commonly used and generally well-tolerated :contentReference[oaicite:13]{index=13}.
• Tetramisole at 5 mg/kg has shown good efficacy with few side effects :contentReference[oaicite:14]{index=14}.
• Oxfendazole 10 mg/kg daily for 5 days is an alternative option :contentReference[oaicite:15]{index=15}.
• Ivermectin has been used extra-label, sometimes combined with fenbendazole, though less commonly reported :contentReference[oaicite:16]{index=16}.

📆 7. Supportive & Aftercare

• Hydration support—subcutaneous or IV fluids if needed.
• Gastric protectants such as famotidine or sucralfate.
• Dietary adjustments: small, bland, low-fat meals.
• Monitoring for vomiting recurrence—especially in multi-cat households.
• Follow-up vomiting samples or lavage may be repeated if symptoms persist.

📈 8. Prognosis & Prevention

With successful treatment:

• Most cats improve significantly, vomiting stops, and weight recovers.
• Prevention in multi-cat environments is essential—prompt removal of vomit and isolation during treatment :contentReference[oaicite:17]{index=17}.
• No known human health risk—zoonosis hasn’t been reported :contentReference[oaicite:18]{index=18}.

📚 9. Case Study: “Mittens”

Mittens, a 3‑year‑old indoor/outdoor cat in a cattery, had daily post-meal vomiting and mild weight loss. Gastric lavage and Baermann testing found O. tricuspis larvae. Treated with a 5-day fenbendazole course + gastric support diet—vomiting ceased within a week, and weight normalized in 3 weeks. No relapse.

🚨 10. When to Reevaluate

• Vomiting persists beyond treatment—repeat diagnostics recommended.
• Multiple cats affected—treat and manage environment.
• Additional signs like melena, severe gastritis, or weight loss warrant further investigation (e.g., endoscopy).

✨ 11. At-Home Care Checklist

• 🕒 Administer full medication course with Ask A Vet reminders.
• 🧼 Clean and remove vomit promptly to prevent spread.
• 🍽️ Feed bland, small meals to reduce irritation.
• ⚠️ Monitor appetite, vomiting, and hydration daily—record in Ask A Vet app.
• 📅 Schedule follow-up vet visits if symptoms return.

❤️ 12. Final Thoughts

Though uncommon, Ollulanus tricuspis can silently undermine your cat’s digestive health with persistent vomiting. Through targeted diagnosis, evidence-based treatment, and thoughtful recuperative care, most cats recover fully. In multi-cat homes, managing environment and hygiene helps prevent reinfection. With Ask A Vet, you'll receive guided support, medication schedules, and vomiting-tracking tools for a confident recovery journey 🐾.

For tailored care plans, tele-support, medication tracking, and expert advice, visit AskAVet.com or download the Ask A Vet app. We’re here to support you and your feline friend every step of the way. 🐱💛