What are canine lung worms?

While a lung worm infection is rare in a dog living in the city, the canine's country cousins aren't so lucky—especially those rural dogs who hunt or are in a field regularly.

A parasite, lung worms infect the respiratory tracts of dogs and live in the windpipe where they pass larvae that are either coughed up, spit out or swallowed and passed in the stool.

Treatment of lung worm infections is usually simple, inexpensive and successful, as long as the infection is treated quickly.


Dogs are infected with lung worms through exposure to another animal carrying the parasite.

Crayfish and snails are often carriers, as are raccoons, which often feed on crayfish. This makes dogs who hunt raccoons especially vulnerable to contracting a lung worm infection.

Lung worms infect puppies when the puppies come into contact with the saliva of an infected animal, eat the faeces of an infected animal, or through their mother's milk if she is infected.

Life Cycle

A female lung worm lays her eggs in a dog's lungs, and the parasite develops through all five stages of its life inside the lung tissue of the infected pet.

Between 32 and 35 days after the infection, the worms mature and begin laying more eggs.

Unlike many other parasites, lung worms do not require any of the parts of their life cycle to take place outside of their host's body.


The primary symptom of a lung worm infection is a chronic cough. Often the cough is worsened when the dog exercises of becomes excited.

While some pets may show no symptoms of the infection, others may become lethargic, not able to exercise and lose weight.

A symptom your veterinarian will look for will be a rise in the dog's white blood cells called eosinophiles.


If your dog has a suspected lung worm infection, the veterinarian will likely perform a fecal examination. The larvae of the lung worms will likely be visible, under microscope, in your dog's faeces.

The veterinarian will also want to get your pet's medical history and do a physical exam, during which she will listen to your dog's lungs through a stethoscope.

She may do a chest x-ray and examine your dog's respiratory secretions.

Veterinarians often will also perform a heart worm test to rule out that type of infection, which has many symptoms similar to a lung worm infection.


The treatment for a lung worm infection is usually a three-day prescription of Panacur, a "de-wormer" that is given for other types of parasite infections. It is relatively inexpensive and easy to administer. In a powdered form, you administer the medication to your pet by putting the correct dosage in moist food each day for three days.

If your dog has had a severe reaction to the infection, the veterinarian may also prescribe a three- to 10-day round of anti-inflammatory medications.


Nearly all dogs make a full recovery from lung worm infections.

The only exceptions would be dogs who already had a compromised immune system or those in whom the infection lingered for months or even years.

In the case of a pet whose lung worm infection went untreated for a length of time, there may be permanent scarring of the lung tissue and the dog may continue to have a chronic cough throughout her life.


There is little to do to prevent a lung worm infection.

With the exception of not letting your dog roam and ensuring that he doesn't eat infected crayfish or snails, the best measure you can take it to be aware of his health.

If he develops a cough, take him to a veterinarian for a fecal examination to determine if lung worm larvae are present in his stool. This will allow you to begin the "de-worming" process before the infection has damaged his lung tissues.

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About the Author

Bethney Foster is social justice coordinator for Mercy Junction ministry, where she edits the monthly publication "Holy Heretic." She is also an adoption coordinator with a pet rescue agency. Foster spent nearly two decades as a newspaper reporter/editor. She graduated from Campbellsville University, receiving a Bachelor of Arts in English, journalism and political science.