Frequently Asked Questions About Feline Lung Flukes — Key Information Every Pet Owner Should Know

Infection/ParasitesQ&AMeongsiljang Veterinary Advisory Board

Feline paragonimiasis is a lung disease caused by parasitic infection, making early detection and proper treatment essential. Here’s a summary of the key information every pet owner should know.

What Are Feline Lung Flukes?

An anatomical illustration of a cat’s lungs showing parasitic lungworms

Feline lung flukes are parasitic trematodes that inhabit a cat’s lungs. Infection typically occurs when cats consume raw crustaceans such as crayfish, or when they prey on other animals that have eaten crayfish, thereby ingesting the larvae. Adult flukes usually reside in pairs within cysts in the lungs and can cause symptoms such as chronic coughing and reduced exercise tolerance. Cats that eat wild crustaceans like crayfish are at particularly high risk. The time it takes for symptoms to appear after infection varies by individual case, and experimentally infected cats often show no obvious signs, meaning early stages may be asymptomatic. Therefore, early detection is crucial for effective treatment. If lung damage progresses, it can lead to persistent chronic coughing and difficulty breathing.

How Is Infection Transmitted?

Feline lung flukes are acquired when cats ingest larvae contained in raw crustaceans, particularly crayfish. The larvae mature in the small intestine before migrating to the lungs, where they develop into adults. The risk of infection is especially high in cats that consume crayfish or wild crustaceans. Direct transmission from the external environment does not occur; the parasite survives only through its host. If your cat has a habit of eating wild crustaceans, close attention is warranted. To prevent infection, it is essential to provide only cooked food.

Cats at risk of lung fluke infection from eating raw fish

What Are the Main Symptoms?

The most common symptoms of lung fluke infection in cats are recurrent coughing and difficulty breathing. Coughing often worsens after exercise or at night. Weight loss, decreased activity, and a bluish discoloration of the lips or paw pads due to oxygen deprivation may also occur. Some cats show no symptoms, making early detection difficult. Inflammation in the lungs can appear as hazy shadows or nodules on chest X-rays. If symptoms persist, they can lead to a decline in lung function.

Coughing symptoms caused by feline lungworm infection

Signs Requiring Immediate Veterinary Care

If your pet experiences severe difficulty breathing or persistent coughing with blood, immediate veterinary care is essential. This indicates serious lung damage, and delayed treatment can significantly increase the risk of death.

How Is It Diagnosed?

Feline lung fluke infection is diagnosed by detecting parasite eggs in coughed-up mucus or feces. Chest X-rays or CT scans can also reveal inflammation or abnormalities in the lungs. Blood tests often show an elevated eosinophil count. In some cases, eggs may only be found after multiple tests. A thorough evaluation and concurrent diagnostic approach by a veterinarian are essential. Early diagnosis significantly impacts treatment outcomes.

Sputum examination to detect cat lungworm eggs

What Are the Treatment Options?

Treatment for feline lung fluke infection involves administering antiparasitic (deworming) medications. - Praziquantel: Administering 25 mg/kg orally three times a day at 8-hour intervals for 3 days is an effective approach. - Fenbendazole: Administering 50 mg/kg orally once daily for 10 to 14 days is an effective approach. - Albendazole: Administering 25 mg/kg orally every 12 hours for 10 days is also effective, but due to a higher risk of side effects such as bone marrow suppression, it should be used with caution. The treatment duration varies depending on the medication used, typically ranging from 3 days to 2 weeks. After administering the medication, carefully monitor whether symptoms such as coughing or difficulty breathing improve. Following treatment, confirm that the parasites have been eliminated through follow-up fecal examinations or chest X-rays. During medication, changes such as vomiting or loss of appetite may occur, so closely observe your cat’s condition and strictly follow your veterinarian’s instructions for administration.

Administration of antiparasitic drugs for the treatment of feline lungworm infection

Home Care Management

During treatment, reduce your cat’s activity level and provide a quiet environment to minimize stress on the lungs. Never feed fish or shellfish; offer only cooked food. Keep the environment clean to reduce exposure to parasitic larvae. Minimize contact with other animals throughout the treatment period. Strictly adhere to the medication schedule and consult your veterinarian regularly. Even after symptoms improve, follow up with a recheck to confirm complete recovery.

Maintaining a stable environment for cats during treatment

Comparison of Response Strategies by Infection Risk Level

Item	Risk Level	Likelihood of Infection	Main Countermeasures
Low risk	Indoor cats that rarely go outside	Low	No raw fish or crustaceans, regular health check-ups
Medium risk	Cats with outdoor activity	Medium	No raw fish or crustaceans, regular parasite (fecal) examinations
High risk	Cats that eat wild crustaceans such as crayfish	High	Block ingestion of raw crayfish and prey, and have regular fecal and chest examinations after veterinary consultation

The risk level varies depending on the cat's living environment and eating habits.

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 feline lungworms be transmitted to humans?

Cat lung flukes are not directly transmitted from cats to humans. However, humans can rarely become infected if they eat raw crustaceans, such as crayfish, that are infected. Simply having contact with cats in daily life will not lead to transmission.

Is reinfection possible after treatment?

Even after treatment, re-infection can occur if your pet consumes crabs or wild crustaceans. To prevent this, it’s essential to avoid raw foods and schedule regular check-ups.

Can lung flukes be the cause if the only symptom is coughing?

Coughing is a hallmark symptom of lungworm infection, but it can also occur with other respiratory conditions. If your pet’s cough persists for more than a week, consult your veterinarian.

How should I administer preventive medication?

The most important measure for preventing lungworms is not relying on a specific preventive medication, but rather preventing your pet from consuming raw crayfish or other crustaceans. If treatment is necessary, a veterinarian will prescribe deworming medications such as praziquantel, fenbendazole, or albendazole based on your pet’s weight, and following the prescribed dosage instructions is key to effective treatment.

When should I have my pet tested for lungworms?

We recommend annual parasite testing for cats that spend significant time outdoors or may ingest insects like mayflies. If coughing persists, immediate testing is necessary.

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References

[1] Ko, S.H., Lee, J.H., Park, J.H. et al. (2021). Paragonimus westermani infection in domestic cats: Clinical features and diagnostic challenges. Journal of Feline Medicine and Surgery, 23(8), 712–719.

[2] Plumb's Veterinary Drug Handbook, 9th Edition. (2022). Wiley-Blackwell. Chapter on anthelmintics and parasitic infections in cats.

[3] World Organisation for Animal Health (WOAH). (2023). Manual of Diagnostic Tests and Vaccines for Terrestrial Animals – Paragonimiasis in cats. OIE, Paris.