In this article

1. How dogs become infected
2. What local slug studies can and cannot tell you
3. The signs can extend beyond a cough
4. Testing is part of a wider investigation
5. Ask what the prevention plan actually covers
6. Garden slug control is a separate safety decision
7. Make prevention a manageable part of normal care

A dog does not have to deliberately hunt snails to encounter lungworm. PDSA explains that infected slugs and snails can be swallowed accidentally, including while eating grass. Lungworm can cause serious disease, and the useful first step is to ask whether your dog's prevention plan specifically covers it¹.

You can have that conversation without treating every garden exploration as an emergency. Tell the practice what your dog tends to eat, where they spend time and what parasite treatments they already receive. Those ordinary details are more useful than guessing the risk from the number of slugs outside tonight.

How dogs become infected

The parasite usually meant by lungworm in UK dog advice is Angiostrongylus vasorum. A September 2026 veterinary review describes adult worms living in the pulmonary arteries and right side of the heart. Dogs and foxes are important hosts; slugs and snails carry a developing stage of the parasite².

Dogs become infected by eating an infected intermediate host, or another host such as a frog carrying infective larvae. Larvae passed in infected dogs' faeces help continue the cycle. The review describes spread beyond the old southern UK hotspots, with fox studies supporting a much wider distribution².

Research has also demonstrated larvae leaving infected molluscs and surviving outside them under experimental conditions. The importance of these possible environmental routes in everyday transmission remains uncertain. A 2021 study makes that limitation clear; a plausible route should not be presented as a measured risk from every slime trail or puddle³.

That distinction matters when deciding what a practical household plan should promise. You can reduce opportunities for eating slugs and discuss appropriate prevention with the practice. You cannot inspect a patch of grass and certify that it presents no possible exposure.

What local slug studies can and cannot tell you

A Guildford study collected 97 slugs and snails from six sites in autumn 2016. Parasite DNA was detected in four specimens, all slugs: four of 44 slugs, or 9.1%, and four of 97 molluscs overall. The positive specimens came from urban and suburban sites⁴.

That supports taking ordinary town and garden environments seriously. It does not mean one in eleven slugs everywhere in the UK is infected, or that a particular encounter gives a dog a nine-percent infection risk. It was a small, local sample using molecular detection, with further work needed on place and season⁴.

The 2021 Brighton and Hove study examined where dogs and molluscs overlapped in seven walking areas. Grassland and vegetated habitats were important places of co-occurrence. The surveys counted hosts and their habitats; they did not directly measure dogs becoming infected during a walk or test a prevention routine³.

Use the studies to ask better questions about your dog's routine. A city postcode is not the whole exposure history, and a countryside walk is not a diagnosis. Tell the practice about local outings and travel, including changes since your last parasite review.

The signs can extend beyond a cough

PDSA lists cough, breathing problems, weight loss, unexplained bruising or bleeding, seizures and collapse among possible signs. These can vary considerably between dogs. Contact your vet promptly if you notice them, and seek emergency help for breathing difficulty, collapse, seizures or serious bleeding¹.

The 2026 review notes that some infected dogs with bleeding problems have no respiratory signs. Others have mild or vague signs, and some infections are initially unnoticed. A dog does not need the complete combination of cough, bruising and breathing trouble before lungworm belongs among the vet's possibilities².

Describe the actual change rather than trying to make the symptoms fit a lungworm story. When did coughing begin? What does the bleeding look like? Is the dog able to do their normal activities? Other causes may need investigation as well, so keep the account open.

Testing is part of a wider investigation

ESCCAP UK and Ireland's diagnostic guidance describes blood antigen testing and examination of faeces using the Baermann technique, which looks for larvae. Faecal testing can require fresh samples from several days because shedding is intermittent. Follow the practice's collection instructions; a single ordinary worm check may answer a different question⁵.

The guidance places lungworm tests within a broader work-up for respiratory, bleeding or neurological signs. A negative antigen result makes infection less likely, but further faecal testing may be appropriate if suspicion remains. Your vet interprets the result alongside the history, examination and other possible explanations⁵.

Testing may also matter before a procedure where bleeding would be a concern. ESCCAP advises considering infection even when signs are not obvious and recommends follow-up testing after treatment. Ask the team whether testing is relevant to your dog's symptoms, planned surgery or local risk⁵.

Question	Why to ask
What is this test looking for?	Antigen and faecal tests examine different evidence of infection5.
How should I collect samples?	Freshness and collection across days can matter5.
What happens after the result?	Results need a clinical plan and sometimes further testing5.

Ask what the prevention plan actually covers

PDSA recommends veterinary advice and a licensed product for lungworm protection. Check the exact indication with the practice rather than assuming a treatment described as a wormer covers every parasite. Bring product names and administration dates so the team can see what is already in place¹.

Ask for a written plan: what is covered, when it is due and what to do if a treatment is missed or you are unsure it was given successfully. Share the record with everyone who arranges care. A reminder works best when it refers to an agreed treatment, rather than the vague instruction to “do the worms.”

Explain if giving a treatment is difficult. You might need a different practical arrangement, a demonstration or help keeping the dates clear. The conversation should leave you knowing how to follow the recommendation and how to get advice when the routine goes off course.

Garden slug control is a separate safety decision

Defra and HSE announced the phase-out of outdoor metaldehyde slug-pellet use in Great Britain by 31 March 2022 because of risks to birds and mammals. This concerns a garden poison, rather than a treatment for the parasite in dogs. Do not regard killing garden slugs as a substitute for veterinary lungworm prevention⁶.

Animal PoisonLine's slug-control leaflet explains that ferric-phosphate products generally have lower poisoning risk, but ingestion can still cause vomiting, diarrhoea, lethargy or abdominal discomfort. Other deterrent materials can also cause problems if eaten. A less toxic formulation should not become something the dog is allowed to investigate by mouth⁷.

If your dog eats a slug-control product, seek immediate professional advice with the packaging available, even before symptoms develop. Move them away from the source and do not induce vomiting or give salt water. The product, amount and dog's circumstances determine what care is needed⁷.

Make prevention a manageable part of normal care

HSE recommends keeping garden pesticides in their original containers, securely closed and out of children's and pets' reach. Its advice also suggests considering non-chemical approaches such as hand removal or physical barriers. Check current authorisation and disposal advice for old garden products rather than using them because they are already in the shed⁸.

You do not need to remove nature from your dog's life. A clear veterinary plan, attention to changing health and sensible garden storage can sit alongside enjoyable walks and time outdoors. Start by checking the record and asking what your particular dog needs next.

Sources and further reading8 sources

The small numbers in the article link to the source behind each fact. Sources open on their own websites.

1. Lungworm in dogsPDSA
2. New Insights Into Pathogenesis, Diagnostics, and Therapeutic Options for Canine AngiostrongylosisJournal of Veterinary Emergency and Critical Care
3. Co-Occurrence of Domestic Dogs and Gastropod Molluscs in Public Dog-Walking Spaces and Implications for Infection …Animals
4. Molecular detection of Angiostrongylus vasorum in gastropods in Surrey, UKParasitology Research
5. Canine Lungworm Angiostrongylus vasorum Diagnostic RecommendationsESCCAP UK & Ireland
6. Outdoor use of metaldehyde to be banned to protect wildlifeDefra / Health and Safety Executive
7. Prevention of poisoning with slug and snail control productsAnimal PoisonLine / Veterinary Poisons Information Service
8. Using pesticides in your garden, home or allotmentHealth and Safety Executive