Dog owners: beware the spread of lungworm in the UK

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Lungworm, which can cause serious health problems in dogs, and can be fatal if not diagnosed and treated, is spreading across the UK. Find out the essential facts about lungworm, and how to keep your dog protected from this potentially fatal parasite.

Slugs and snails can carry lungworm larvae, and dogs become infected when they eat these infected molluscs

Lungworm (Angiostrongylus vasorum) is a particularly nasty parasitic worm that can cause serious health problems and, sadly, can even be fatal to dogs.

Unfortunately, whilst it used to be confined to certain areas, it has now spread throughout much of the UK, and new cases are being reported in many different areas of the country.

The good news is that if it is caught in time it is treatable. And even better, it can be prevented.

What is lungworm and why is it so dangerous for my dog?

Lungworm (A. vasorum) is a potentially fatal parasite of dogs. The adult worms lives in the heart and major vessels of infected dogs, and their larvae hatch in the lung tissue; where they can cause breathing problems such as coughing. Lungworm can also result in some more unusual symptoms such as blood clotting issues and neurological problems, as well as more general symptoms like vomiting, diarrhoea and lethargy. Untreated, lungworm can be fatal.

As more cases of lungworm are reported around the UK, many vets are urging dog owners to take the growing threat of lungworm seriously and take steps to protect their dog against this potentially fatal parasite.

How do dogs become infected with lungworm?

Slugs and snails can carry lungworm larvae, and dogs become infected when they eat these infected molluscs, which can happen intentionally or accidentally when dogs rummage through undergrowth, eat grass or drink from puddles or outdoor water bowls etc. Lungworm larvae can also be released into the slime trail;1 meaning areas a slug has crawled over could pose a potential risk. Once swallowed, the larvae travel to the dog’s heart where they develop into adult lungworms. Frogs can also carry the larvae, posing an additional risk to dogs.

slugs and snails can carry lungworm larvae

Why is lungworm spreading in the UK?

Infected dogs will pass lungworm larvae out in their poo. This then infects more slugs and snails, and these infected molluscs can then pass lungworm on to other dogs.

Foxes can also become infected with lungworm, and play a part in spreading the parasite around the country. Research suggests that the percentage of foxes in the UK that are infected has more than doubled in the last ten years to 18% - this research showed that prevalence in foxes was as high as 50% in the South-East.2

With more people travelling in the UK with their pets, and foxes roaming the towns and countryside, the parasite is likely to continue to spread around the country.

Where is lungworm found in the UK – and is it near my area?

Lungworm used to be found only in certain ‘hotspots’ in the UK, mainly in the South of England and Wales. However, recent studies show that lungworm is spreading throughout much of the UK, and it is now also endemic in Central England, with an increasing number of cases being reported in Northern England and Scotland.

You can see whether cases have been reported in your area by visiting this handy lungworm map. But remember, it is important to be vigilant against lungworm wherever you live in the UK.

How common is lungworm in the UK?

A survey by researchers at the Royal Veterinary College in London found that one in five vet practices in the UK have reported at least one case of lungworm in a dog.3

This lungworm map shows cases of lungworm that have been reported across the UK, making it clear that much of the country is affected–it is now widely accepted as being endemic across much of the UK.

How do I know if my dog has lungworm?

The signs of lungworm can be easily confused with other illnesses, so it is important to consult your vet immediately if your pet displays any of the following:

  • Changes in behaviour – depression, lethargy or seizures
  • Breathing problems – coughing or tiring easily
  • General sickness – weight loss, poor appetite, vomiting or diarrhoea
  • Poor blood clotting – for example excessive bleeding from minor wounds, nose bleeds, bleeding into the eyes or paleness around the eyes and gums indicating possible anaemia

Dogs can show just one of these symptoms, or a combination of them, or may even show no symptoms at all in the early stages.

Can my dog be treated if he has lungworm?

The good news is that treatment for lungworm is available and if it is caught early enough, most dogs will make a full recovery.

If you suspect your dog may be infected, book an appointment with your vet immediately.

How can I prevent lungworm?

The great news is that lungworm is avoidable. It can be prevented with a regular monthly worming regime, available from your vet.

There are two important things to remember. Firstly, not all wormers are effective against lungworm, so talk to your vet about a suitable product. Secondly, lungworm prevention must be given monthly. Worming every three months (which is often advised for other parasites such as round and tapeworm) will not be effective at preventing this parasite.

Some people find it useful to set a monthly reminder to stay on top of this – it is definitely better to be safe than sorry when it comes to this nasty and potentially fatal parasite.

For further information on preventing lungworm, see our guide to lungworm treatment and prevention.


1 Conboy G et al., Parasitol Res (2017), 116: S41-S54

2 Taylor et al., (2015),142 (9); 1190-5

3 Kirk et al., Vet Record (2014), 175, 118

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Date of review October 2021

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