Lungworm: What are the risks?

Lungworm (Angiostrongylus vasorum) is a parasitic worm that can cause serious health problems and even be fatal to dogs. It was first seen in 1975 and used to be confined to certain areas of the UK. It has now been re-labelled an emerging disease. The risks of infection are higher in the south, but it has now spread throughout much of the UK. On a positive note, if caught in time, it is treatable, and can also be prevented. 


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

Lungworm is a type of parasitic worm affecting dogs, and also foxes, who are often implicated in spreading the disease from area to area. With the number of urban foxes in London, it means there is a relatively high risk of infection. 

Once infected, adult lungworm live in the host dog’s heart and the major blood vessels supplying the lungs, where they often cause a host of potentially serious problems. The developing larvae cause inflammation of the lung tissue leading to coughing as well as less specific signs such as lethargy, vomiting and diarrhoea. Presence of lungworm can lead to clotting issues signified by nosebleeds, bleeding within the whites of the eyes or skin, or blood in the urine or faeces. If not treated it can be fatal. This type of lungworm thankfully poses no risk to humans.

How do dogs get lungworm?

Only snails and slugs carry the infectious late-stage larvae. When a dog (or fox) eats a snail or slug (either on purpose or accidentally), the larvae migrate from the gut wall through the liver tissue and into the bloodstream on its way to the heart (the right ventricle and pulmonary arteries, to be precise) where they mature into adults. There they breed, and their eggs hatch into larvae which enter the airways. From the lungs, the larvae are coughed up, swallowed, and passed within faeces, finally infecting passing slugs and snails. 

Slime trails can also contain larvae, making anything the snail or slug has crawled over a risk. This includes bowls, toys and grass, which a dog may eat. Young dogs may be more at risk, purely because they may be more curious. 

Although a dog cannot directly catch lungworm from another dog or fox, an infected fox (or dog) in the area can infect local snails and slugs, thus increasing the risk for everyone in the locality. 

How common is it?

Once rare in the UK, it has spread into new areas and now cases are being reported across the country, including the Midlands, north of England and Scotland, as well as expanding in the already established hot spots in the south of England and Wales.

Researchers have recently found that while the number of infected foxes has grown rapidly in Britain, the growth was most significant in Greater London, with approximately three in every four foxes found to be carrying lungworm. Land type, dog density and climatic factors may be involved, but the simple presence of foxes locally increased the risk of lungworm infection in dogs five-fold. 

It is not just Greater London where lungworm prevalence in foxes is on the rise. Bristol University published a study in 2015 which found 18.3% of foxes across the UK were found to be carrying lungworm. This was more than double what was found in a similar study published 7 years before.

These foxes infect local slugs and snails, putting our pet dogs more at risk. Not all slugs or snails contain lungworm larvae, but according to an almost unbelievable Countryfile statistic, an average British garden is home to more than 20,000 slugs and snails. The risk of a dog encountering a lungworm host is therefore high.

It’s also thought that more people now travel around the UK with their pets, spreading this parasite further and further to local fox populations and thus, if preventative measures are not taken, also to the local dog population. It is now accepted that it is endemic across much of the UK. Wider recognition, vigilance and testing throughout the veterinary profession may also explain some of the increase in reported cases. Ticks, fleas and canine lungworm are all likely to benefit from milder winters and warmer summers, thus climate change may be another factor in the emergence of this disease. 

One in five practices in the UK have reported at least one case of lungworm. Importantly, as lungworm can be difficult to diagnose, confirmed cases may not represent all cases actually seen. Our vets may recommend using blood, faecal or lung fluid samples to look for evidence, alongside tests to check for other causes of signs such as a cough or bleeding. We can get false negatives with these tests so sometimes we recommend treating for lungworm to cover all bases.

How is it treated?

Thankfully, lungworm often does not require invasive or costly treatment if caught early. It may be as simple as changing from one anti-parasite product to another (moxidectin-based spot-ons will kill the parasite, and both moxidectin and milbemycin spot-ons and tablets will prevent it from developing). However, if the symptoms are advanced or the level of infection is severe there is a greater likelihood of permanent damage.

How do I reduce the risks?

  • It’s advisable to add an anti-lungworm preventative into your anti-parasite routine wherever you live, but especially here in London. Not all wormers prevent this type of worm, and treatments are a prescription-only medication, needing to be given monthly to successfully prevent infection. Please speak to a member of our team for more information on protecting your pet. 
  • Remove snails and slugs in your garden when possible, and try to prevent your dog from swallowing them. Don’t leave toys out overnight as your dog may inadvertently eat a hiding slug or their slime. Wash outside water bowls regularly and always pick up your dog’s poop to limit the spread of disease. 
  • It’s not advisable to use slug bait as certain types of slug bait are very toxic to dogs if eaten.
  • There are many conditions in dogs that cannot be prevented, so despite its potentially serious nature, the silver lining with lungworm is that it’s risk can be removed relatively easily.

If you require further advice of information, please contact your local Goddard vet today.