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Slugs, Snails and Lungworm: Protecting Your Dog in the UK

Lungworm (Angiostrongylus vasorum) is a parasitic worm that can cause severe illness and death in UK dogs — and it is spread by one of the most common garden creatures: slugs and snails. Awareness of this disease has grown significantly in recent years, but many dog owners are still unaware of the risk. This guide explains everything you need to know.

What Is Lungworm and How Do Dogs Get It?

Angiostrongylus vasorum, commonly called lungworm, is a parasitic worm that lives in a dog's heart and the blood vessels supplying the lungs. Dogs become infected by accidentally (or deliberately) eating slugs, snails, or their slime trails — which can be present on toys, water bowls, or grass.

The larvae are deposited in slugs and snails by infected foxes, which are a major reservoir of the disease in the UK. When a dog eats an infected mollusc, the larvae migrate through the gut wall, travel to the heart and pulmonary arteries, and develop into adult worms. The adult worms then produce larvae that are coughed up, swallowed, and passed in faeces — completing the cycle.

Lungworm is not spread directly between dogs. However, the parasite has spread geographically across the UK over the past two decades and is no longer confined to the South East, where it was historically concentrated. PDSA and the RCVS advise that owners across the whole of the UK should be aware of the risk.

Slugs are particularly active in damp, mild conditions — which describes much of the UK climate for a large part of the year. Dogs that sniff at or eat grass, play with toys left outside, or drink from outdoor water bowls are at risk.

Symptoms of Lungworm Infection

The symptoms of lungworm can be subtle at first, which is one reason the disease is sometimes diagnosed late. The parasite disrupts the dog's ability to clot blood normally, which leads to a distinctive bleeding tendency. You might notice unusual bruising, prolonged bleeding from minor cuts, or blood in urine or faeces.

Respiratory symptoms include coughing, wheezing, and breathing difficulties — reflecting the worms' presence in the heart and lungs. Some dogs develop general signs including lethargy, weight loss, reduced appetite, and vomiting or diarrhoea. Neurological signs such as seizures or wobbliness can occur if the parasite migrates to unusual locations, including the spinal cord or brain.

The PDSA notes that lungworm can be mistaken for other conditions including kennel cough, heart disease, or even a general bacterial infection. Any dog showing unexplained bleeding alongside respiratory signs should be assessed by a vet as a matter of urgency.

Puppies and young dogs appear to be at higher risk of severe illness, possibly because they are more likely to eat slugs and snails and have less developed immune responses. However, dogs of any age can be affected.

Prevention: What You Can Do

The good news is that lungworm is preventable with regular parasite treatment. Monthly prescription anti-parasitic products — such as those containing milbemycin oxime or moxidectin — are effective against lungworm and are available from your vet. These are prescription-only medicines in the UK and require a consultation or written prescription to obtain.

Standard over-the-counter flea and worm treatments do not protect against lungworm. If your dog is currently on a non-prescription wormer, speak to your vet about whether it is appropriate for your dog's level of risk.

Beyond medication, practical measures help reduce exposure. Bring outdoor toys inside overnight, empty and refill water bowls regularly, and supervise your dog when they are sniffing in grass or leaf litter — particularly in the evening or after rain when slugs are most active. Teach a reliable 'leave it' command, which can prevent your dog from eating found objects.

Foxes are a significant reservoir host and are present in both rural and urban environments across the UK. In areas with high fox populations, the background risk from contaminated slugs is correspondingly higher. Urban dog owners should not be complacent.

Treatment and Vet Costs

Lungworm is treatable if caught early. The same anti-parasitic drugs used for prevention can be used at higher or more frequent doses to treat an active infection. Your vet will likely recommend blood tests to assess the impact on clotting ability and may prescribe supportive medication to address symptoms.

A diagnosis typically involves a consultation (£40–£65), blood tests (£80–£150), and may include chest X-rays (£150–£300) or a specific Baermann larval test. The Angio Detect rapid test, now widely available in UK practices, can give a result within minutes during a consultation.

If the dog's condition is severe — for example, if there is significant internal bleeding or respiratory failure — hospitalisation and intensive care will be required. This can cost £500–£2,000 or more. Dogs that are treated early generally recover well, but delayed treatment can result in irreversible organ damage.

The cost of monthly preventative treatment is typically £10–£20 per month, depending on your dog's size and the product used. Prevention is both more reliable and far cheaper than treatment.

Find the Right Vet with CompareMyVet

Regular preventative care for lungworm requires a good ongoing relationship with a vet who knows your dog. If you are looking for a vet that offers competitive prices on prescription parasite treatments and routine consultations, CompareMyVet can help you compare local practices at app.comparemyvet.uk.

Under the CMA's 2026 reforms, vets must now publish their standard prices, making it easier than ever to compare the cost of consultations and treatments across practices near you. You can also request a written prescription to source preventatives elsewhere if your vet's prices are high.

Read more about how written prescriptions work and your rights as a pet owner on our dedicated written prescriptions guide.