Lungworm in Dogs

Dogs can be infected by several different lungworms, and they are not equally serious. The one that worries vets most is Angiostrongylus vasorum, sometimes called “French heartworm,” which lives in the heart and the large blood vessels of the lungs. Two others — Crenosoma vulpis and Oslerus osleri — live in the airways themselves and tend to cause a more straightforward cough.

Angiostrongylus vasorum (French heartworm)

This parasite is spread when a dog eats an infected slug or snail — or accidentally swallows one while playing with toys, drinking from puddles or eating grass. It can cause coughing and exercise intolerance, but its most dangerous feature is interference with normal blood clotting, which can lead to unexplained bruising, nosebleeds or internal bleeding.

Crenosoma vulpis & Oslerus osleri

These airway lungworms typically cause a chronic, dry cough that does not respond to ordinary cough treatment. Oslerus forms small nodules at the base of the windpipe that a vet may see on a bronchoscope, while Crenosoma is more common in dogs that scavenge or hunt.

Treatment in dogs

Several dewormers are effective. Fenbendazole is widely used for the airway lungworms, usually given daily for several days. Products containing moxidectin (often combined with imidacloprid as a spot-on) are commonly used for A. vasorum. Because dosing and duration vary by parasite and by patient, your vet should confirm the protocol.

Use the calculator for a fenbendazole estimate, then talk to your vet about the best product for your dog’s situation.

Quick reference

• Most serious: Angiostrongylus vasorum — affects clotting; needs urgent care.
• Most common cough cause: Crenosoma vulpis in scavenging dogs.
• Main route of infection: eating slugs, snails or contaminated grass/water.