Lungworm in dogs: symptoms, spread and prevention

This guide is general information, not veterinary advice. If you're worried about your dog, speak to your vet.

Lungworm (Angiostrongylus vasorum) is a parasite that can cause severe illness and even death. Despite its name, it travels around the whole body (PDSA). The good news is that it's preventable, and usually treatable if caught early (PDSA; Blue Cross).

Symptoms to look out for

Lungworm symptoms can be vague and varied, depending on how many worms there are and which organs they reach (PDSA). In mild cases, owners may not notice anything (Blue Cross). Signs include:

• Coughing (PDSA; Blue Cross)
• Breathing problems: fast, heavy or noisy breathing (PDSA; Blue Cross)
• Not wanting to exercise (Blue Cross)
• Loss of appetite, vomiting or diarrhoea (Blue Cross)
• Weight loss (PDSA; Blue Cross)
• Unexplained bruising or bleeding, including nosebleeds, or a small cut that bleeds for longer than usual (PDSA; Blue Cross)
• Seizures (fits), or a wobbly or abnormal walk (PDSA; Blue Cross)
• Collapse and shock (PDSA)
• Blindness (PDSA)

How dogs catch lungworm

• Slugs and snails: dogs catch lungworm by eating infected slugs and snails, which often happens by accident while eating grass or drinking outside (PDSA).
• Frogs: Blue Cross says dogs can also catch it from larvae in infected frogs (Blue Cross).
• By accident: dogs can swallow infected slugs that are on a toy or on their fur, or on discarded food in the park (Blue Cross).

Lungworm doesn't pass directly from dog to dog. Infected dogs pass larvae in their poo, which infects more slugs and snails, which are then eaten by more dogs. That's how it can spread quickly (Blue Cross). Inside the dog, adult worms live in the heart and blood vessels, and start producing larvae after about 28 days (Blue Cross).

Where in the UK is lungworm found?

Sources agree it's spreading, but describe the picture a little differently:

• PDSA says lungworm infection is becoming much more common and is now a risk to dogs across much of the UK (PDSA).
• Blue Cross says it's becoming more common across areas of the UK, and that cases are higher in southern England and South Wales, so it's worth talking to your vet if you travel there with your dog (Blue Cross).

Ask your vet about the risk where you live and walk.

How to prevent lungworm

• Use a wormer that covers lungworm. PDSA says it's easy to prevent lungworm by making sure your dog's worming routine includes lungworm protection, using a veterinary licensed product (PDSA).
• Check where it comes from. PDSA says there are currently no lungworm treatments available without a prescription. Products sold without one, in supermarkets, pharmacies, pet shops or online, aren't veterinary licensed (PDSA). Blue Cross says standard pet shop wormers don't cover lungworm (Blue Cross), and that many common worming treatments aren't effective against it (Blue Cross).
• Ask how often. Your vet can advise which product suits your dog and how often to use it (Blue Cross).
• Discourage slug and snail snacking. Make sure your dog doesn't eat slugs, snails or frogs (Blue Cross).
• Refresh outdoor water bowls. Change the water in outdoor bowls regularly (Blue Cross).

Our guide to how dog illnesses spread covers other everyday parasite risks.

Diagnosis and treatment

No test is totally reliable, but most vets use a blood test. They may also check a poo sample, though larvae aren't present in every sample, and in severe cases an X-ray can show changes in the lungs (Blue Cross).

Treatment depends on how ill your dog is (PDSA). Your vet will kill the worms with a deworming product and monitor your dog carefully, because killing lots of worms at once can cause a reaction. Seriously ill dogs may need hospital care, such as oxygen, a fluid drip or a blood transfusion (PDSA).

If lungworm is caught and treated early, the outlook is likely to be good. Infections that cause breathing difficulties or seizures generally have a poorer outlook, and severe cases can be fatal (PDSA). Blue Cross says most dogs recover if treated early, though a small number may have lung scarring afterwards (Blue Cross).

Can people catch lungworm?

No. Blue Cross says lungworm isn't known to infect humans (Blue Cross). The parasite that causes lungworm in dogs is also different from the one that affects cats (Blue Cross).

Finding a vet in Liverpool

Your vet can prescribe lungworm prevention and advise on local risk. Browse our Liverpool vets directory to find a practice near you.

Out-of-hours emergencies in Liverpool: Medivet 24 Hour Alder, 410 Eaton Road, West Derby, L12 3HG, says it is open 24 hours a day, 365 days a year. Call 0151 220 4668 (Medivet, checked 18 Oct 2026). Vets Now Liverpool, based in the PDSA Pet Hospital on Woolfall Heath Avenue, Huyton, L36 3YD, opens from 6pm on weeknights, from noon on Saturdays, and all day on Sundays and bank holidays. Call 0151 271 5727 (Vets Now, checked 18 Oct 2026). Always ring before you set off, and ask your own vet which service covers their out-of-hours calls.

More in our dog health series

• How dog illnesses spread
• Dog vaccinations explained
• Puppy vaccination timeline
• Parvovirus in dogs
• Kennel cough
• Leptospirosis in dogs

See all our dog health and first aid guides

There are no affiliate links on this page. Affiliate disclosure. This guide is general information, not veterinary advice. Always speak to your vet.