The pulmonary worm

What is it?

It is a worm, whose scientific name is Crenosoma vulpis, which lives mainly in the feline bronchi, but occasionally infects dogs too. It measures between 3.5 mm and 16 mm in length.

Clinical signs

Infected dogs suffer from bronchitis that causes chronic cough and nausea.


The infection is acquired by ingestion of snails or by contact with an object or with liquid exposed to snail mucus.

The parasite cycle

The larvae of the parasite found in the snail, which is ingested by the dog, are absorbed in the dog's intestine through his liver and reach it's bloodstream.

Subsequently, the larvae spread to the heart and lungs where they develop and mature.

Once grown, worms lay eggs, in which new larvae are found, in the dog's bronchioles.

After a first maturation, the larvae are expectorated, swallowed, excreted in the feces of the animal and then ingested by a snail where they continue their development.

The duration of the parasite cycle is approximately nineteen days. It begins when the dog becomes infected by eating the snail and ends when adult worms lay eggs.

Is the parasite contagious to humans?

Luckily they aren't! 

The diagnosis

The diagnosis is confirmed when larvae are seen in the dog's stool. These have a typical appearance: a conical head and a pointed tail.

Following the death of the animal, adult worms can also be observed in the bronchi upon necropsy.

The treatment

There are various medications, sold under prescription, that are safe and effective in killing the parasite. 


In dogs, the medication usually used to prevent common parasitic infections is probably not effective in the case of the pulmonary worm.

It is therefore best to minimize hunting or keep dogs on a leash or in a fenced yard to try to prevent their access to snails.