Lungworm: Slugs, Coughing, and Bleeding
Lungworm is spread by slugs and snails and has spread across the UK. Most dogs cough, but some bleed. What a 2026 review says about risk and prevention.
Written by thecanineledger
If your dog has unexplained bruising, a nosebleed, blood in the eye, coughs up blood, or struggles to breathe, go to a vet now. If your dog has a cough that won’t settle, or tires easily, see your vet within a day or two.
Our note: This advice is ours. The review lists these signs but gives no owner advice.
Lungworm (Angiostrongylus vasorum) is a parasite that lives in the blood vessels of the lungs and the right side of the heart. Dogs catch it from slugs and snails. In the UK it was once found mainly in southern England and Wales. Based on studies in foxes, it “is now considered endemic across the country”, according to a 2026 review (Elgueta et al., Journal of Veterinary Emergency and Critical Care 2026).
While most infected dogs have breathing signs, the more frightening problem is bleeding. That can show up in ways owners wouldn’t link to a worm.
→ Deworming: How Often Depends on Your Dog
1. The source
What it is. A review by four UK-based authors, summarising published research. It is not a new study.
Funding. A veterinary group’s research fund paid for the work. Two authors work for veterinary groups. The authors declare no conflicts of interest.
2. How dogs catch it
Slugs and snails. These carry the infective larvae. Dogs are infected by eating an infected slug or snail.
Other hosts. Frogs and chickens can also carry the larvae, and eating them can infect a dog.
Infected dogs shed larvae. Larvae pass out in the faeces, which is how the cycle continues. Dogs without obvious illness may shed them for long periods.
Foxes. Foxes are the main wild reservoir.
Young dogs. Dogs of all ages can be infected, but “younger dogs, especially under 1 year of age, seem more likely to become infected”. This may be because young dogs scavenge more.
Our note: The review says larvae shed by slugs survive in the laboratory, but it doesn’t know whether dogs catch the infection from slime on toys, water bowls or grass.
3. The signs
Breathing. Cough and difficulty breathing are the most common signs.
Bleeding. Bleeding problems are the second most common. They can include small red spots or bruises on the skin, bleeding into the eye, nosebleeds, coughing up blood, blood in the urine and bleeding after surgery.
The brain. In one large study the review cites, more than 10% of dogs had neurological signs linked to bleeding in the brain or spinal cord.
Heart. In longer-standing cases, high blood pressure in the lungs and heart failure can follow, with weakness, fainting or a swollen belly.
→ Emergency Signs in Dogs: When to Go Now, Not Tomorrow
4. Outlook
The review says “the prognosis is highly variable and is related to the severity of clinical signs at presentation.” Prompt treatment can lead to full recovery.
Bleeding worsens the outlook. In one large study the review cites, 76.9% of dogs with bleeding survived to discharge, against 94.8% of those without.
Figures vary. Studies report bleeding in anywhere from 5.6% to 71% of infected dogs. Elsewhere, the review gives 35% to 60%. Much of the data comes from specialist hospitals, where dogs tend to be sicker.
Our note: The review gives two different ranges for bleeding: 35% to 60%, and 5.6% to 71%.
5. Prevention
Monthly treatment. Licensed preventive treatments are given monthly. Less frequent worming, or unlicensed products given monthly, “probably reduces the risk of infection, it does not eliminate the possibility”.
No product names. We name no products. Your vet can advise which treatment fits your dog and area.
Our note: The review doesn’t say whether all UK dogs need monthly prevention. Ask your vet about your dog’s risk.
→ Deworming: How Often Depends on Your Dog
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “Lungworm is only in the south of England” | No longer. It is now considered endemic across the UK, based on fox studies. |
| “Lungworm only causes coughing” | No. Bleeding is the second most common problem. |
| “Dogs catch it from slug slime on toys” | Not shown in dogs. It is possible in the laboratory; the field risk is unknown. |
Sources
- Elgueta I, Lewis D, Morgan ER, Helm J. New insights into pathogenesis, diagnostics, and therapeutic options for canine angiostrongylosis. J Vet Emerg Crit Care 2026. ⚠️ narrative review. Funded by a veterinary group’s research fund
Always confirm with your vet before acting on anything on this page.