Guide to Lungworm: what is it, how to spot the signs and protect your dog

Lungworm can be fatal to dogs and is on the rise in the UK, with thousands of cases and fatalities being reported. Our expert guide explains what lungworm is, how to spot the signs and what you can do to protect your dog from this potentially deadly parasite.


Lungworm has been a common problem in Southern England but there has been a spike in cases in Northern England and Scotland. Head Veterinary Nurse Laura Hawkins and British Veterinary Association (BVA) Past President Gudrun Ravetz explains more about how to spot the signs and treat lungworm.


Our expert guide explains what lungworm is, how to spot the signs and what you can do to protect your dog from this potentially deadly parasite.

What is lungworm?

Lungworm (Angiostrongylus Vasorum) is an infection caused by the round worm parasite called Angiostrongylus Vasorum (AV). Slugs and snails carry the lungworm larvae and dogs generally become infected when they play with and consume them. They can also come into contact by eating grass, drinking from puddles, outdoor water bowls or toys that have been left outside in grass as the larvae can be left in the slugs and snails slime trail.

Unlike many diseases, lungworm cannot be passed from dog to dog.  The worm needs slugs and snails to act as a host in order to grow and develop. Frogs can also be used as a host.

Incidents of lungworm being diagnosed in dogs were originally more prevalent in the South East and in South Wales, but there have been an increasing number of cases in other parts of the country, including Scotland. However it is still a rare diagnosis.


How is lungworm contracted?

Dogs pick up the AV larvae after eating infected slugs and snails. The larvae mature and migrate around the body, ending up in and around the lungs. Worms will then lay eggs which mature into larvae in the dog’s body and are then coughed up by the dog, swallowed and passed in the faeces, which will go on to infect more snails and slugs… And the cycle starts again

Garden pests

Slugs and snails are hermaphrodites – each individual has both male and female sex organs, so any two individuals can mate and reproduce, and a single individual can even self-fertilise to reproduce. Eggs form in clusters in the soil, beneath leaves, or in other areas where the soil is damp. The eggs can lie dormant in the soil for months and hatch only when conditions are suitable.

Slugs and snails can carry lungworm larvae/Credit: Getty

Agronomist Ryan Hudson says numbers will generally increase during a warm and wet period, such as a wet spring, which can encourage higher adult numbers resulting in more eggs laid for the autumn.


Foxes can become infected with lungworm, and have been massively implicated in the spread of the parasite across the country. Studies show that 18% of foxes across the UK are now infected (50% in the south east)

What breed of dog is most at risk from lungworm?

Dogs of all ages and breeds can become infected but studies have shown that some breeds are more commonly affected than others, although why this is the case is not yet known.

Spaniels are one of the most commonly affected breeds. It is thought this could be the result of breed defect or that the breed is commonly outdoors and used for working.

Young dogs can be at great risk of lungworm so give toys a regular clean/Credit:Getty

Younger and greedy dogs also seem to be more prone to picking up the parasite due to their inquisitive nature.

What are the signs and symptoms lungworm in dogs?

Many dogs won’t initially show symptoms of Lungworm and it can go unnoticed for quite some time as the symptoms can easily be confused with other illnesses.

  • Some dogs will show no symptoms but can shed the larvae in their faeces for significant periods of time.
  • The severity of clinical signs can vary from subclinical – where the owner will not notice any illness – to mild symptoms, severe symptoms and death.
  • Dogs will often cough due to the physical presence of the worms in their lung area.
  • Problems associated with bleeding, such as blood in urine, vomiting blood and petechial haemorrhage (pink blood spots on the gums) may be signs of lungworm.
  • Owners may also notice a severe reddening around the eye – scleral haemorrhage.

Other symptoms of lungworm can include:

  • Breathing problems
  • Coughing
  • Tiring easily
  • Poor blood clotting
  • Excessive bleeding from even minor wounds or cuts
  • Nose bleeds
  • Weight loss
  • Poor appetite
  • Vomiting
  • Changes in behaviour
  • Depression
  • Lethargy
  • Anaemia
  • Diarrhoea
  • Seizures

What is the treatment of lungworm in dogs and cats?

  • Vets can test for the presence of the worm in a number of different ways and many practices will have an in-clinic test that can give a result quickly.
  • The infection can be very serious and can cause death. Treatment is aimed at killing the worms but occasionally treatment can worsen the clinical signs due to the large number of dying worms.
  • There are preventive medications that owners can get from their vets to try and reduce the risk of infection. Owners can also restrict their dogs from accessing areas where there are slugs and snails.
  • Avoid leaving dog toys out in the garden where they may be covered in snails and slugs, which your dog may then ingest.
  • Lungworm is not common but owners should discuss the risks with their veterinary surgeon who can then provide the correct preventive treatment.

How do you prevent lungworm in dogs and cats?

Many Veterinary practices will routinely carry out a lungworm test before performing surgery on a dog or to check that they have been receiving a preventative treatment. This aims to reduce the risk of bleeding post-surgery which can be fatal if the dog has lungworm.

Clean dog water bowls regularly to prevent your dog contracting lungworm/Credit: Getty

To reduce the chances of your dog contracting lungworm, simple methods of dog hygiene should be carried out, such ensuring faeces is picked up and disposed of correctly and not leaving toys or bowls outside. Obviously, it is harder to stop a dog drinking from puddles or eating slugs and snails if this is their nature, but a simple monthly spot on treatment can be used to treat and prevent lungworm. Alternatively,  if your dog will eat a tablet (try hiding in a small piece of meat or in their dog food) tablet versions also prevent lungworm if taken monthly.

Why is lungworm on the rise?

The reason for the increased numbers of dogs diagnosed with lungworm is not completely clear but may be due to a number of factors, including changes in the environment that increase the number of snails. The fact that diagnostic tests are becoming more available may also have increased the number of reported cases.

This lungworm map of the UK reports on all recorded cases in your area.

Screen Shot 2019-03-26 at 11.43.00
Recent cases of lungworm in the UK

In 2019 there have already been a number of lungworm cases reported with warmer seasons thought to be contributing to an increase in cases.