Lungworm infection (Aelurostrongylus abstrusus) is a parasitic respiratory disease in cats spread by ingesting infected slugs, snails, or prey animals. Signs mimic asthma — coughing, wheezing, and labored breathing — but lungworm is treatable with antiparasitic medication once diagnosed. Outdoor and hunting cats are at highest risk.
Last reviewed: June 2026
What Is Lungworm in Cats?
Cat lungworm most commonly refers to infection with Aelurostrongylus abstrusus, a metastrongyloid nematode that lodges in the terminal bronchioles and alveoli of the lungs. Cats become infected by ingesting molluscs (slugs, snails) that carry the larvae, or by eating paratenic (transport) hosts such as frogs, lizards, or birds that have ingested infected molluscs. Once in the lungs, female worms lay eggs that hatch into larvae, trigger an inflammatory response, and cause progressive respiratory disease. As described in Ettinger's Textbook of Veterinary Internal Medicine, A. abstrusus infection is probably more prevalent than clinical case reports suggest because mild infections often go undiagnosed. The AAFP-AAHA Feline Life Stage Guidelines, 2021 recommend year-round parasite prevention for outdoor cats specifically to reduce lungworm exposure.
Signs of Lungworm in Cats
- Chronic cough — the most consistent sign; may be dry and hacking or productive
- Wheezing and labored breathing — heard particularly after activity
- Increased respiratory rate at rest — normal is 20–30 breaths per minute; over 40 is concerning
- Open-mouth breathing — in severe cases
- Reduced exercise tolerance — the cat tires quickly or avoids play
- Nasal discharge — mucopurulent in some cases
- Weight loss — in chronic, heavy infections
- Occasionally asymptomatic — light infections may be found incidentally on routine fecal examination
Diagnosis
Lungworm is diagnosed by identifying larvae in respiratory secretions or feces using the Baermann technique (a specialized larval flotation method). Thoracic radiographs show a diffuse bronchiointerstitial or alveolar pattern. Bronchoalveolar lavage may be needed for definitive diagnosis in coughing cats with negative fecals. Costs: fecal Baermann test $50–100; chest X-rays $150–300; BAL requires sedation and runs $300–600.
Treatment
Antiparasitic treatment is effective. Commonly used agents include:
- Fenbendazole (50 mg/kg daily for 3 weeks — exotic-licensed use, dose per Plumb's Veterinary Drug Handbook)
- Selamectin (topical spot-on; labeled for some parasites, used off-label for lungworm)
- Moxidectin/imidacloprid combination (Advantage Multi) has demonstrated efficacy in European studies
Anti-inflammatory medications (prednisolone) reduce the inflammatory component when coughing and breathing distress are severe. Most cats improve significantly within 2–4 weeks of treatment.
The AAFP Feline Retrovirus Guidelines, 2020 context is relevant here because cats hunting outdoors face combined risk of both viral disease (FeLV/FIV) and parasitic infections including lungworm — integrated parasite + retrovirus screening is recommended for outdoor cats.
Prevention
- Keep cats indoors or in secured outdoor enclosures
- Use monthly broad-spectrum parasite prevention (selamectin, moxidectin combinations)
- Prevent hunting of slugs, snails, frogs, and lizards
- Annual fecal screening for outdoor cats
When to See a Vet
Call your vet today if:
- Your outdoor or hunting cat develops a new cough that lasts more than a week
- You notice wheezing or labored breathing after activity
- Your cat's resting breathing rate is elevated (count breaths for 60 seconds while sleeping — over 30/min is abnormal)
- Your cat is losing weight despite eating
Go to the ER immediately if:
- Your cat is open-mouth breathing or breathing with visible effort
- Breathing rate at rest exceeds 40 breaths per minute
- Gums appear blue, grey, or white (cyanosis)
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Frequently Asked Questions
Can indoor cats get lungworm? Primarily outdoor cats get lungworm because they hunt slugs, snails, and prey animals. Indoor cats face very low risk unless they occasionally go outdoors. If an indoor cat develops a chronic cough, lungworm is far less likely than asthma or herpesvirus-related respiratory disease.
How is cat lungworm diagnosed? The Baermann fecal technique detects first-stage larvae in feces, but shedding is intermittent and false negatives occur. Chest X-rays show a lung pattern consistent with lungworm, and bronchoalveolar lavage (examining lung wash fluid) provides definitive identification of larvae. Total diagnostic cost: $200–600.
How long does lungworm treatment take in cats? Most cats respond within 2–4 weeks of antiparasitic treatment. Severe cases with significant lung inflammation may need a longer course of anti-inflammatory medication. Recheck chest X-rays at 4–6 weeks confirm resolution. Treatment medication itself typically costs $30–80 for a full course.
Is cat lungworm contagious to humans or dogs? Aelurostrongylus abstrusus does not infect humans or dogs — it is cat-specific. However, dogs have their own lungworm species (Angiostrongylus vasorum) transmitted by the same mollusc intermediate hosts. Cleaning up pet feces promptly limits environmental contamination.
What does lungworm treatment cost in cats? Diagnostics (Baermann fecal + chest X-rays): $200–400. Treatment medication: $30–80. Follow-up exam and recheck X-rays: $150–300. Total typical case: $400–800. Severe cases requiring hospitalization for respiratory support cost $500–1,500+.
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