Could My Dog Have Lungworm? Symptoms, Diagnosis, and Treatment

Lungworm causes coughing, breathing problems, bleeding and sometimes neurological signs in dogs. This guide explains signs, tests, treatment, home care and when to seek emergency help.

What is lungworm in dogs?

Lungworm is a general name for parasitic worms that infect a dog's respiratory system and sometimes blood vessels. In dogs the most important species are Angiostrongylus vasorum (often called the French heartworm), Crenosoma vulpis, and Eucoleus (Capillaria) aerophilus. These parasites cause a range of signs from mild coughing to life-threatening bleeding, respiratory failure and neurological problems.

Lungworm is more common in some regions (notably parts of the UK, Europe and some areas of North America) and risk is higher where dogs eat or investigate slugs, snails, frogs or wild gastropods, or where they scavenge wildlife feces.

Sources: Merck Veterinary Manual, regional veterinary public health resources.

Common signs and symptoms

Signs can develop gradually or suddenly depending on worm species, parasite load and complications (for example coagulopathy). Common symptoms include:

• Coughing (moist or dry), sometimes with exercise intolerance
• Rapid or difficult breathing (tachypnea, dyspnea)
• Lethargy, reduced appetite
• Weight loss and poor body condition with chronic infection
• Intermittent bleeding (nosebleeds), bruising or bleeding gums with Angiostrongylus vasorum
• Sudden collapse, fainting or weakness
• Neurological signs (seizures, ataxia, behavioral changes) if worms or bleeding affect the nervous system
• Lameness or sudden rear-limb weakness (can be related to blood clots or bleeding)

When to See a Vet Immediately

If your dog shows any of the following, seek veterinary care right away:

• Severe difficulty breathing, open-mouth breathing, blue-tinged gums or tongue
• Sudden collapse or repeated fainting
• Uncontrolled bleeding (nosebleeds, blood in vomit or stool), large bruises
• Seizures, severe disorientation or sudden paralysis

How veterinarians diagnose lungworm

A veterinarian will combine history, clinical exam and tests. Common diagnostic steps:

• Detailed history: exposure to slugs/snails, recent hunting, travel to endemic areas
• Physical exam: lung sounds, mucous membrane color, neurological exam
• Fecal testing: Baermann technique to recover larvae (useful for many lungworms). Multiple samples on different days increase sensitivity.
• Fecal flotation or direct smear: may find eggs or larvae of some species.
• Blood tests: CBC (look for eosinophilia, anemia), chemistry profile, coagulation tests (PT, aPTT), D-dimer if clotting problem suspected.
• Serology / antigen tests: commercial antigen or antibody tests exist for Angiostrongylus vasorum (for example the AngioDetect/IDEXX tests) and can be helpful when fecal tests are negative.
• Thoracic radiographs (chest X-rays): assess lung patterns (bronchial, interstitial or alveolar changes), heart size and complications.
• Advanced imaging (CT) or bronchoscopy in complex cases.

Differential diagnosis (common causes ranked by likelihood)

When a dog has coughing or breathing problems, the veterinarian will consider several possibilities. These are common causes ranked roughly by how often they are encountered in practice (actual prevalence varies by region):

Your veterinarian will use the history, exam and tests to determine which of these is most likely.

Treatment options (what the vet will do)

Treatment depends on the species of lungworm, severity and complications. Important points:

• Anthelmintics: Several drugs are effective against canine lungworm but the choice and duration depend on species and local guidelines. Commonly used agents include:

• Supportive care:

• Management of coagulopathy or bleeding:

• Monitoring: Repeat fecal testing, follow-up chest X-rays and bloodwork to document clearing of infection and resolution of complications.

Home care and prevention steps

While diagnosis and treatment must be managed by a veterinarian, owners can help with supportive home care and prevention:

• Follow the veterinarian’s medication and recheck schedule precisely; do not stop treatments early.
• Rest and restrict strenuous activity until your vet says it’s safe; exercise can worsen breathing or clot-related problems.
• Keep the dog calm and in a cool, well-ventilated area if breathing is increased, and minimize stress.
• Prevent access to slugs, snails, frogs and areas with heavy wildlife fecal contamination. Consider excluding your dog from garden areas known to have gastropods or to dig in compost/wet vegetation.
• Promptly collect and dispose of feces; routine deworming and preventive products (monthly heartworm/lungworm preventives where recommended) reduce risk.
• Check with your vet about regular fecal screening or regional prevention protocols — geographic risk influences the best prevention plan.

Red Flags — Seek Emergency Care

Go to the nearest emergency clinic if your dog has any of these:

• Severe or worsening difficulty breathing, gasping, open-mouth breathing
• Collapse or repeated fainting episodes
• Ongoing or heavy bleeding from nose, mouth, rectum or unusual bruising
• Seizures, loss of coordination, inability to rise
• Sudden severe worsening after starting treatment (new bleeding or collapse)

What to expect at the vet visit

Bring a focused history: duration of signs, exposure to wildlife or slugs, previous deworming and travel history. The vet will likely perform physical exam, blood tests (CBC, chemistry, clotting), fecal testing (Baermann and possibly antigen testing), and chest X-rays. Severe cases may be hospitalized for oxygen, IV fluids, blood products and close monitoring. Treatment may start before all test results are back if the vet suspects a life-threatening infection.

Prognosis

Prognosis varies by species and severity. Many dogs recover fully with appropriate treatment, especially when detected early. Dogs with severe respiratory failure, uncontrolled bleeding or extensive neurologic disease have a more guarded prognosis and may require intensive care.

Key Takeaways

• Lungworm (including Angiostrongylus vasorum and other species) can cause coughing, breathing problems, bleeding and neurological signs in dogs.
• Diagnosis typically uses fecal testing (Baermann), antigen/antibody tests, bloodwork and chest X-rays; repeated testing may be necessary.
• Treatment requires veterinary-prescribed anthelmintics and supportive care; emergencies (respiratory distress, collapse, bleeding, seizures) require immediate veterinary attention.
• Prevent by reducing exposure to slugs/snails/wildlife, keeping dogs from scavenging and discussing regional preventive protocols with your veterinarian.

Frequently Asked Questions