Lungworm in Dogs: What Owners Need to Know
Lungworm is one of those parasites most dog owners have heard about, but it can be hard to know exactly what to look out for.
One of the main lungworms affecting dogs is Angiostrongylus vasorum. Adult worms live in the blood vessels supplying the lungs and around the right side of the heart.
The signs of infection can vary quite a bit. Some dogs develop breathing problems or a cough, while others can show unusual bleeding, weakness or, in some cases, neurological problems.
How do dogs get lungworm?
Slugs and snails play an important role in the life cycle of Angiostrongylus vasorum.
Dogs can become infected by swallowing an infected slug or snail carrying the infective stage of the parasite.
That doesn’t necessarily mean your dog has to be deliberately eating slugs from the garden.
A 2021 study looking at dogs and gastropods in public dog-walking areas found that dogs and slugs or snails regularly used the same spaces, highlighting how opportunities for exposure can arise during normal outdoor activity.
What signs can lungworm cause?
There isn’t one single set of symptoms that every infected dog will develop.
A 2021 study of dogs naturally infected with Angiostrongylus vasorum found a wide range of clinical presentations, showing why the infection can sometimes be difficult to recognise from symptoms alone.
Possible signs include:
coughing
difficulty breathing
reduced tolerance for exercise
weakness or tiredness
unexplained bleeding or bruising
nosebleeds
neurological signs in some dogs
Some infected dogs can also have relatively mild or non-specific signs.
Why can lungworm cause serious illness?
Although we call it lungworm, Angiostrongylus vasorum is actually a cardiopulmonary parasite.
Adult worms live primarily in the pulmonary arteries, the blood vessels carrying blood from the heart towards the lungs.
Recent research continues to show that infection can cause significant damage to the lungs and blood vessels. A 2023 study examining four severely affected dogs found adult worms in the pulmonary arteries as well as lung inflammation, haemorrhage and damage to pulmonary blood vessels.
These were severe cases and shouldn’t be taken as representative of every infected dog, but they demonstrate why lungworm can sometimes become a serious condition.
Can lungworm affect blood clotting?
Yes. One of the more unusual features of Angiostrongylus vasorum infection is its association with bleeding and clotting abnormalities in some dogs.
This means signs may not always look like a straightforward lung problem.
Unexplained bruising, nosebleeds or other abnormal bleeding can sometimes form part of the clinical picture.
Not every infected dog develops bleeding problems, and these signs can have many other causes, so they should always be investigated by a vet rather than assumed to be lungworm.
How is lungworm diagnosed?
Lungworm can’t reliably be diagnosed from symptoms alone.
One method involves examining faeces for the parasite's larvae using a technique known as the Baermann test.
More recent research has also highlighted some of the limitations of diagnostic testing.
A 2022 study found that the amount of larvae shed in faeces was related to the adult worm burden, but also showed why factors such as sample handling and timing can affect faecal testing.
Depending on the individual dog, your vet may recommend faecal testing alongside blood tests, imaging or other investigations.
Can lungworm be prevented?
There are veterinary parasite-control options that cover Angiostrongylus vasorum, but not every worming programme provides the same protection.
That is why it is worth checking exactly what your dog's current parasite treatment covers rather than assuming that all wormers protect against lungworm.
The right parasite-control programme will depend on the individual dog, including their lifestyle and likely exposure.
Your vet can advise you on what is appropriate for your dog.
Can I reduce my dog's risk?
It may not be possible to prevent every encounter with slugs and snails, particularly if your dog spends plenty of time outdoors.
It is sensible to discourage dogs from eating slugs and snails and to regularly check outdoor bowls and toys for them.
These precautions cannot guarantee that a dog will avoid infection, so they shouldn’t be treated as a substitute for veterinary advice on parasite control.
When should I contact my vet?
Speak to your vet if your dog develops a persistent or unexplained cough, difficulty breathing, unusual bleeding or bruising, weakness or other symptoms that worry you.
Breathing difficulty, collapse or significant unexplained bleeding should be treated as urgent.
These symptoms do not automatically mean a dog has lungworm. A number of other conditions can cause similar signs, and veterinary examination and testing may be needed to find the cause.
Is your dog protected against lungworm?
If you’re unsure whether your dog's current parasite-control routine covers lungworm, East Limerick Vets can look at your dog's lifestyle and individual risk and advise you on an appropriate parasite-control plan.
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