Lungworm Infections in Pets

Lungworm is an emerging infectious parasite in our dog population in Ontario. There are multiple types of lungworms found across the world, but in Ontario we are currently concerned about the Fox Lungworm (Crenosoma vulpis). As the name depicts, foxes are the natural host of lungworm. The lungworm resides in the upper airways of foxes and dogs.

Life cycle

A fox infected with lungworm will have adult worms living in their upper airways (trachea, bronchi, bronchioles). These worms lay eggs which are coughed up, swallowed and passed in the stool. Snails (and slugs) consume the infected feces where the larvae mature. For the parasite to be transmitted to dogs, they must ingest an infected snail. Inside the dog, the immature lungworms will penetrate the stomach wall and migrate to the airways. Once there, they mature into adult lungworms and the cycle continues.

Clinical Signs

The presence of lungworms in the upper airways can cause inflammation and irritation. This leads to coughing, retching, difficulty breathing and/ or discharge from the nose.


Diagnosing lungworm relies on identifying them in the feces or in the upper airways. This can be accomplished through fecal testing or tracheal endoscopy to visualize the worms. For best results with the fecal test, it is recommended to collect a fresh fecal sample over 3 days. The sample is sent off to the lab to perform a Baermann test to detect the presence of eggs.  Finding lungworm eggs in feces can be difficult. A negative test does not necessarily mean there isn’t an infection present.

Treatment and Prevention

Luckily, killing lungworm is relatively simple. It involves using monthly dewormer medication that can be obtained from your veterinarian. The same medication is used monthly to prevent against lungworm infections.

So if your dog decides to dine on escargot, we can keep them safe from lungworm infections!

Please feel free to contact Coxwell Animal Clinic if you have any questions about lungworm. Our staff would be happy to answer any of your questions!

By Dr. Ashley Woo