If Your Cat Keeps Coughing — Lungworm Infection Symptoms, Transmission Routes, and Treatment Timing

Infection/ParasitesDiseasesMeongsiljang Veterinary Advisory Board

Feline lungworm infection is a respiratory parasitic disease caused by lungworms that parasitize the lungs and bronchi. The main symptoms are chronic coughing and difficulty breathing, and the primary route of infection is through the ingestion of slugs or lizards.

What Is Feline Lungworm Infection?

Feline lungworm disease is a respiratory parasitic condition caused by the lungworm Aelurostrongylus abstrusus, which parasitizes the lungs and bronchioles, triggering inflammation. What’s truly important to note is that while early signs may appear as mild coughing, leaving the condition untreated can lead to chronic lung damage. Cats that roam outdoors freely or hunt prey such as slugs, lizards, or mice are at particularly high risk of infection.

How Does Infection Occur? — Transmission Routes and Life Cycle

The primary route of infection for lungworms is the direct ingestion of intermediate hosts, such as snails and slugs. Infection can also occur when cats hunt and consume frogs, lizards, birds, or mice that have eaten snails. Once a cat ingests an infected host, the larvae are absorbed in the intestines and travel through the bloodstream and lymphatic system to the lungs. The larvae settle in the lungs, mature into adults around the bronchioles, and lay eggs. The hatched larvae are coughed up, swallowed, and then passed in the feces. Snails in the environment contaminated by these feces ingest the larvae, continuing the life cycle.

Checklist of Main Symptoms of Lungworm Infection

Chronic cough: A dry cough or one with phlegm that persists for several weeks or longer.

Rapid breathing or panting: A noticeably increased respiratory rate, even while at rest.

Wheezing: A whistling sound during breathing caused by narrowed airways.

Nasal discharge and eye discharge: Mucous secretions increase if a secondary bacterial infection develops.

Lethargy and decreased appetite: Reduced activity levels and a poor appetite.

Weight loss: Significant weight loss can occur as the condition becomes chronic.

A cat showing signs of coughing and lethargy

When Immediate Emergency Veterinary Care Is Needed

If your cat is panting with its mouth open, if its gums or tongue appear pale or bluish, if its abdomen is noticeably expanding and contracting with each breath, or if it has refused food and water for more than 24 hours, seek immediate veterinary care. These signs may indicate a life-threatening emergency involving a sudden decline in lung function.

How Is It Diagnosed?

The Baermann technique is a diagnostic method that isolates live first-stage larvae from feces by allowing them to migrate into water, where they can then be examined under a microscope. Unlike fecal flotation, which detects eggs, this method is specifically suited for directly identifying larvae of the lungworm *Aelurostrongylus abstrusus*, making it the most commonly used diagnostic test. However, both the Baermann technique and fecal flotation have relatively low sensitivity. Therefore, if clinical suspicion remains despite a negative result, it is advisable to repeat the tests several times at intervals of a few days. On chest radiographs, early-stage infection may present with a bronchial or focal alveolar pattern, which can progress to a broncho-interstitial pattern as the disease advances. Computed tomography (CT) provides a more detailed assessment of pulmonary lesions. A definitive diagnosis can be achieved by collecting bronchial secretions via bronchoalveolar lavage (BAL) and confirming the presence of larvae.

Treatment Methods — Deworming Medication and Supportive Care

The cornerstone of treatment is administering deworming medication. The most common approach is oral fenbendazole at a dose of 50 mg/kg for 3 to 14 days. Other options include selamectin (applied twice, one month apart), topical combinations of imidacloprid and moxidectin, or eprinomectin spot-on solutions, which can be effective with a single application. Milbemycin may also be given orally for six weeks at two-week intervals. For severe respiratory symptoms, bronchodilators or short-term steroids may be used as adjunctive therapy. Your veterinarian will determine the exact dosage and duration based on your pet’s weight and condition. After treatment is complete, a follow-up Baermann test is performed; if no larvae are detected, the case is considered cured.

A veterinarian auscultating a cat’s chest at the animal hospital

Home Management and Care Points

To prevent reinfection during treatment, the most effective approach is to keep your pet indoors. If outdoor access is necessary, avoid flower beds or damp grassy areas where slugs and snails are common, and prevent your pet from hunting prey. If coughing or difficulty breathing occurs, minimize stress and avoid environments with high humidity or dust. In multi-cat households, we recommend separating the cats during the treatment period. Clean up feces daily and always wash your hands thoroughly afterward.

A healthy cat resting comfortably indoors

Preventing Reinfection and Breed-Specific Precautions

Kittens under six months of age and immunocompromised senior cats may experience a more rapid worsening of symptoms. Brachycephalic breeds, such as Persians and Exotic Shorthairs, have naturally narrower airways, which can lead to more severe respiratory symptoms. Even after full recovery, it is advisable for outdoor cats to undergo fecal examinations every six months and to receive monthly deworming preventatives consistently.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can heartworms be transmitted to humans?

Feline lungworms are rarely transmitted to humans. However, it's important to always wash your hands after handling feces as a basic hygiene practice.

Can even indoor cats get infected with heartworm?

Indoor-only cats are at very low risk. However, if slugs or snails have entered your balcony or yard, or if your cat has ever been outdoors, there is a possibility of infection.

How long does treatment take?

Typically, we recheck with a Baermann test four weeks after administering dewormer for two to four weeks. Depending on the severity of the infection, the entire process may take two to three months.

Is there a separate preventive medication?

Monthly preventive treatments, such as topical formulations containing selamectin or a combination of imidacloprid and moxidectin, are effective in preventing heartworm disease. Consult with your veterinarian to choose the product best suited for your cat’s individual health needs.

Does coughing always mean a heartworm infection?

Not necessarily. Coughing in cats can stem from a variety of causes, including asthma, bronchitis, heart disease, and hairballs. To pinpoint the exact cause, it is essential to have your cat examined by a veterinarian.

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References

[1] Traversa D, Di Cesare A, Conboy G. Canine and feline cardiopulmonary parasitic nematodes in Europe: emerging and underestimated. Parasit Vectors. 2010;3:62.

[2] Little SE (ed). The Cat: Clinical Medicine and Management, 2nd Edition. Elsevier Saunders, 2012.

[3] Ettinger SJ, Feldman EC, Côté E (eds). Textbook of Veterinary Internal Medicine, 8th Edition. Elsevier, 2017.

[4] Bowman DD. Georgis' Parasitology for Veterinarians, 10th Edition. Elsevier Saunders, 2014.