Strongyloidiasis in Cats: Vet Guide 🐱🦠 2025

By Dr Duncan Houston BVSc, veterinarian & founder of Ask A Vet.

Strongyloidiasis (also called threadworm infection) is caused by Strongyloides spp.—small parasitic nematodes such as S. felis, S. planiceps, S. tumefaciens, and occasionally zoonotic S. stercoralis. Though rare and often underdiagnosed, it can cause diarrhea, malabsorption, respiratory signs, and even systemic disease—especially in kittens, immunocompromised cats, and shelter populations. This comprehensive 2025 guide covers:

• 🧠 Overview of Strongyloides species in cats
• 🔎 Transmission & life cycle
• 🚨 Clinical signs & at-risk groups
• 🧪 Diagnostic protocols
• 💊 Treatment recommendations
• 🛡️ Prevention and environmental hygiene
• 🤝 Ask A Vet telehealth support

🔬 Strongyloides Species in Cats

Four species are known to infect cats:

• S. felis – first described in India, occasionally reported; resides in small intestine :contentReference[oaicite:2]{index=2}.
• S. planiceps – identified in wild felids, similar small intestinal niche :contentReference[oaicite:3]{index=3}.
• S. tumefaciens – lives within colonic nodules; discovered during necropsy :contentReference[oaicite:4]{index=4}.
• S. stercoralis – zoonotic species found rarely in cats, more common in dogs and humans :contentReference[oaicite:5]{index=5}.

🔄 Life Cycle & Transmission

Strongyloides have complex life cycles with autoinfection potential:

• Infection via ingestion or skin penetration by infective filariform larvae :contentReference[oaicite:6]{index=6}.
• Larvae migrate through tissues—skin & lungs to small intestine, mature into reproducing females :contentReference[oaicite:7]{index=7}.
• Eggs hatch in gut; L1 larvae shed or develop into autoinfective stages in GI tract :contentReference[oaicite:8]{index=8}.
• Autoinfection cycle may lead to prolonged shedding and hyperinfection, especially in immunocompromised cats :contentReference[oaicite:9]{index=9}.

🚨 Who’s At Risk?

• Kittens and young cats—due to immature immunity :contentReference[oaicite:10]{index=10}.
• Shelter and stray populations with poor hygiene—stray cats prevalence ~29%, owned ~9% :contentReference[oaicite:11]{index=11}.
• Immunocompromised cats or those on long-term steroids—risk of disseminated disease :contentReference[oaicite:12]{index=12}.

📋 Clinical Signs

Signs vary with age and infection intensity:

• Gastrointestinal: chronic diarrhea (often blood/mucus), weight loss, malabsorption, occasionally vomiting :contentReference[oaicite:13]{index=13}.
• Pulmonary: coughing or tachypnea during lung larval migration :contentReference[oaicite:14]{index=14}.
• Dermatologic: dermatitis and skin lesions from larval entry—"larva currens" :contentReference[oaicite:15]{index=15}.
• Severe: lethargy, dehydration, bronchopneumonia, systemic spread in immunosuppressed cats :contentReference[oaicite:16]{index=16}.

🧪 Diagnosis

• Fecal Baermann test: gold standard for detecting L1 larvae :contentReference[oaicite:17]{index=17}.
• Fecal flotation: may miss larvae from intermittent shedding :contentReference[oaicite:18]{index=18}.
• Colonoscopic biopsy: can reveal parasites in colonic nodules from S. tumefaciens :contentReference[oaicite:19]{index=19}.
• Repeat sampling: often needed due to sporadic shedding :contentReference[oaicite:20]{index=20}.
• Serology/PCR: used in some settings but limited availability in cats :contentReference[oaicite:21]{index=21}.

💊 Treatment Protocols

No targeting drugs are specifically registered in cats—but off-label therapies used:

• Ivermectin: 200 µg/kg SC or PO, repeat every 4 days for 3–4 doses :contentReference[oaicite:22]{index=22}.
• Fenbendazole: 50 mg/kg PO daily for 3–14 days as alternative or adjunct :contentReference[oaicite:23]{index=23}.
• Albendazole: higher doses sometimes used but riskier :contentReference[oaicite:24]{index=24}.
• In hyperinfection or autoinfection: prolonged ivermectin plus fenbendazole for 7–14 days :contentReference[oaicite:25]{index=25}.

⚕️ Supportive Care

• Fluid therapy for dehydration and electrolytes.
• Antidiarrheals, nutritional support, and gut-healing supplements.
• Antibiotics for secondary bacterial overgrowth or pneumonia.
• Chest X-rays and oxygen support if respiratory signs present.
• Monitor for eosinophilia, weight, hydration, and symptom resolution.

🛡️ Prevention & Environmental Management

• Isolate infected cats until treatment completed and negative fecals confirmed.
• Clean bedding, litter boxes, and all environments—larvae survive in moist soil :contentReference[oaicite:26]{index=26}.
• Routine deworming and hygiene protocols for shelters and breeding facilities.
• Limit exposure to contaminated soil/water, skin penetration risks.

📆 Prognosis & Monitoring

• Mild cases in adults—excellent with treatment and supportive care.
• Kittens and immunocompromised cats—risk of chronicity or severe disease; prognosis depends on early treatment :contentReference[oaicite:27]{index=27}.
• Verify clearance with fecal testing 2–4 weeks after treatment completion.
• Extend therapy if larvae persist or relapse occurs.

🤝 Ask A Vet Telehealth Support

• 📸 Guide initial symptom evaluation—diarrhea, coughing, skin changes.
• 💬 Aid in choosing suitable treatment option and dosing schedule.
• 📆 Support monitoring during therapy and through follow-up fecals.
• 🔄 Offer advice on infection control, hygiene, and environmental management.

✅ Key Takeaways

• Strongyloidiasis is rare but potentially serious in cats, especially kittens and shelter populations.
• Diagnosis relies on Baermann fecal exams and, sometimes, colonic biopsy.
• Treatment includes ivermectin and/or fenbendazole—with prolonged courses in heavy or autoinfection cases.
• Supportive care and infection control are vital to recovery.
• Prognosis is good with timely treatment; follow-up testing is essential.
• Ask A Vet telehealth guides you every step—from diagnosis through clearance.

📞 Final Thoughts

While uncommon, strongyloidiasis can harm young or immunocompromised cats. Early detection, effective treatment, and sanitation minimize risks. With Ask A Vet’s expert telehealth guidance, you’ll be well-equipped to care for your cat through diagnosis, treatment, and clearing infection. 😊

Need help dosing, interpreting results, or setting a hygiene plan? Visit AskAVet.com and download the Ask A Vet app anytime!