Lungworm in Dogs: Understanding Causes, Symptoms, and Effective Treatments

Brief summary

• Lungworm is caused by a parasitic worm picked up from slugs and snails
• It is not directly contagious, but infected dogs will pass eggs that can then hatch into larvae and infect other dogs and foxes.
• Symptoms include coughing, breathing problems, gastrointestinal symptoms and unexplained bleeding
• Treatment is available but can be difficult once an infection is well-established
• It is recommended to use anti-parasite medication regularly in most dogs to prevent infection

What is lungworm?

The disease lungworm is caused by a worm called Angiostrongylus vasorum. The larvae of these worms are found in slugs and snails. Dogs get infected with lungworm by eating or playing with slugs and snails. The larvae are even present in the snail and slug slime trails, meaning dogs can become infected through grass, water or outside toys. Not every slug or snail carries these worm larvae, but cases have been rising over the last decade. 

The larvae grow and mature inside the dog. Adult worms are about 2.5cm long and migrate to the dog’s heart and blood vessels, where they cause damage to vital structures. After around a month, the adult worms produce their own larvae, which cause further problems. 

The new larvae are coughed up, eaten and pass out in the infected dog’s poo. They can then re-infect more slugs and snails, and the cycle begins again. Dogs cannot transmit lungworm directly to each other but will shed larvae out into their environment. Humans can’t catch lungworm from their pets - although they can get other worms, such as tapeworm, from dogs. 

Can any dog get lungworm?

All dogs - of any breed, age and size - are susceptible to lungworm. There are some differences by region across the UK, with southern regions generally more affected.

Generally, lungworm cases are increasing across the UK. Foxes also carry the worm, and a rise in the number of affected foxes is causing an increase in cases in dogs. A recent study showed that an average of 18% of UK foxes are infected, with this number rising to 50% in the South-East areas and a huge 74.4% in Greater London.

What are the symptoms of lungworm in dogs?

The symptoms of lungworm are quite varied, but often include:

• Coughing
• Breathing harshly, heavily or rapidly (panting)
• Lethargic, not wanting to play or exercise
• Not eating well
• Vomiting and diarrhoea
• Weight loss
• Bleeding problems such as unexplained bruising, prolonged bleeding from cuts and grazes and nosebleeds
• Pale gums

On rare occasions, the worms can infect the blood vessels of the eyes and brain, causing neurological symptoms such as acute blindness or seizures.

Lungworm can be an extremely dangerous disease, and in around 9% of cases is fatal. Mild symptoms are often difficult to spot but can progress rapidly to severe disease.  

Lungworm diagnosis

If your dog has any possible lungworm symptoms, speak to your veterinary surgeon. They will be able to examine your dog closely for any concerns. There is a blood test for lungworm, and your vet may also take a poo sample to examine under the microscope. Changes to your dog’s airways and lungs can be examined using X-rays.

How to treat lungworm in dogs

If lungworm infection is caught early, the treatment is relatively simple. Some dog worming tablets and other anti-parasitics are effective against the Angiostrongylus vasorum parasite, so your vet can dispense a suitable medication.

However, treating severely infected dogs is more complicated. Worming treatments can kill the worms, but the dead parasites can block up blood vessels and cause severe inflammatory reactions. This is why prevention is so important, as well as being vigilant for potential infections. Lungworm infection can also have long-term consequences for health, such as scarring of the lungs.

Preventing lungworm in dogs

Luckily, there are ways to minimise the risk of lungworm to your pet.

Some worming treatments for dogs can act preventatively against this parasite. Speak to your vet about whether lungworm is common in your area and what level of protection your dog needs. For most dogs, adding lungworm prevention tablets into your routine parasite treatments is recommended. 

There are also some ways to reduce the risk of your dog being exposed to lungworm. Keep outside water sources clean and fresh, and bring toys and chews indoors overnight. Pick up your dog’s faeces quickly and always practise good hygiene principles. Try to keep dogs from eating slugs and snails where possible. 

Have there been any studies looking into lungworm in dogs?

Yes, research shows that younger dogs, especially those under two years old, are more likely to get infected with lungworm compared to older dogs. However, this illness can happen at any age. The reason younger dogs might get it more often could be because they eat, play, and explore differently than older dogs. Also, their immune systems aren't fully strong yet. It's important to know that any dog can get this disease, no matter their gender or breed. That said, some breeds like Cavalier King Charles Spaniels, Staffordshire Bull Terriers, Labrador Retrievers, and dogs used for hunting have been reported more often to have this infection.

Need advice and information on lungworm in dogs?

For expert advice on recognising, preventing and treating lungworm in your dog, contact your local vet.

Find your nearest vet using our Find a Vet page, or speak to a vet online using Online Vets.