Puppy Alfie in a garden

Lungworm in dogs

Lungworm is a condition which is becoming more common across areas of the UK. It is caught when a dog or cat eats snails, slugs and frogs, and can be fatal if not treated.

What is lungworm?

Lungworm is caused by a parasitic worm that can travel around your dog's body through their blood vessels and affect the heart, lungs and other parts of the body.

Symptoms of lungworm in dogs

Diagnosing lungworm can be difficult because symptoms vary, but they can include:

  • coughing
  • breathing problems
  • not wanting to exercise
  • loss of appetite
  • vomiting or diarrhoea
  • weight loss
  • if a dog gets a minor injury, like a small cut, it might bleed for longer

Speak to your vet straight away if you think your dog might have lungworm.

How do dogs catch lungworm?

Dogs get lungworm by eating larvae found in infected snails, slugs or frogs. They can also accidentally eat infected slugs if they are on a toy or their fur.

The lungworm larvae then grow inside the dog and adult lungworms move through their body to live in their heart and blood vessels. In severe cases, this can cause heart problems, breathing problems and pneumonia. 

In mild cases, infection can remain unnoticed by owners. After about 28 days the worms start to produce their own larvae which can lead to serious problems. 

It can cause haemorrhages in the lungs, liver, intestine, eyes and spinal cord, but also pretty much anywhere in the body. If left untreated, it can be fatal in severe cases. The good news is that lungworm is usually treatable.

Dogs cannot pass the disease directly from dog to dog but they will pass the larvae in their faeces. This then infects more slugs and snails who are eaten by more dogs, so the disease can spread quickly.


The parasite that causes lungworm in dogs and cats is caused by a different worm.

Preventing lungworm in dogs

Talk to your vet about regular lungworm treatment and prevention, particularly if you travel with your dog around southern England or South Wales as cases are higher in these areas.

Regular anti-parasite treatment

There are currently many worming treatments available through a prescription from your vet. These often cover lungworm, so if your pet is at risk your vet can advise you which product will suit them and how often should be used.

Other preventative measures:

  • Make sure your dog does not eat slugs, snails or frogs.
  • Change the water in any outdoor water bowls regularly.
  • If you spot slugs and snails in your garden or local parks then be extra vigilant when out with your dog and always consult your vet as soon as possible if your dog becomes unwell.

Testing for lungworm

Your vet will ask you about any symptoms your dog might have and may do a blood test. They can also examine a sample of a dog’s faeces (poo) under the microscope to help diagnose lungworm, although this is not 100 per cent reliable as there are not always lungworms present in every sample. 

In more severe cases, an X-ray will also show changes or abnormalities in their lungs.

Treatment for lungworm

Most dogs will recover from lungworm if caught and treated early. The type of medication given will depend on how severe the condition is. However, a small number of dogs may have lung scarring afterwards. 

If left untreated, lungworm can do more harm causing inflammation and, in severe cases, internal bleeding and organ failure. This might mean your dog needs more treatment, so prevention is always better than cure. Sadly, in some cases, it can be fatal.

Can humans get lungworm?

No, lungworm is not known to infect humans. 

There are, however, other types of worms – roundworms, tapeworms, hookworms and whipworms – which can be transmitted from pets to humans, so it's crucial that regular worming takes place at least four times a year. Some tapeworms can also be passed on through infected fleas, but this can be prevented with regular flea treatment. 

Find out more about basic healthcare in dogs.

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• 7 November 2022

Next review

• 7 November 2025

Approved by
Róisín Bolger

Veterinary Surgeon MRCVS