Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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As the name of the disease implies, feline lungworm is caused by parasitic worms which live in the lungs of infected cats. 

ere are several helminth worms which have been reported to cause lungworm disease in cats :

  • Aelurostrongylus abstrusus (the most common cause)
  • Filaroides trostratus
  • Osleroides massinoi
  • Troglostrongylus brevior
  • Troglostrongylus subcrenatus

In the case of Aelurostrongylus abstrusus adult worms lay their eggs in the small airways of the lungs (the bronchioles and alveolar ducts). When the eggs hatch the larvae that emerge damage lung tissue before they are coughed up, swallowed and passed out  in the cat's faeces. Once in the environment the larvae need to be eaten by another host (eg birds, molluscs or rodents) which is called an intermediate host. Cats then get re-infected when they eat their prey and the larvae migrate from the gastrointestinal tract to the lungs where they develop into adults , and the lifecycle of the worm begins again.

Breed Occurrence
There are no specific breed predispositions to developing this disease, however cats that hunt birds, slugs or snails and rodents are most at risk to contract the parasite, as these can be intermediate hosts for the larval stage of the parasite.


Many cats that have lungworms present show no signs at all. When signs do occur the cat usually has a large number of worms present, and they include  :

  • Coughing
  • Difficulty breathing (called dyspnoea)

Damage to the lungs and airways can lead to secondary infections and pneumonia.

The diagnosis is confirmed by identifying early stage larvae of the worm  in the faeces of infected cats. The faeces is examined using the Baermann technique, however eggs are not shed all the time, and so repeated testing is often needed before they are found.

Several drugs have been used to treat lungworm in cats including :

  • Benzimidazoles
  • Ivermectin

Many infected cats do not show any signs of disease and the condition is self-limiting , the cat naturally eliminating it's worm burden in 3-4 months. The prognosis is good for most treated cats with heavy parasite burdens, unless severe secondary pneumonia develops.


Updated October 2013