Lungworm in Dogs: Signs, Risks and How to Ask About Prevention

Lungworm in dogs is an infection with a parasitic worm that spreads through the whole body and not just the lungs, according to the PDSA. Dogs catch it by swallowing slugs or snails, often by accident, and it can cause severe illness and even death. It is far easier to prevent than treat, so speak to your vet about protection.

At a glance

• What it is: a parasite carried by slugs and snails that can affect the heart, lungs and other organs.
• Who it affects: any dog that might swallow a slug or snail, including dogs that graze on grass or drink from outdoor bowls and puddles.
• Urgency: urgent if your dog has signs. The PDSA says to contact your vet immediately.
• Vet needed? Yes, for diagnosis, treatment and prescription prevention.

Signs to look for

The signs are vague and vary, because they depend on how many worms are present and which organs they reach. The PDSA lists coughing, fast or noisy breathing, weight loss, unexplained bruising or bleeding, seizures, collapse and blindness. Blue Cross adds reluctance to exercise, loss of appetite, vomiting or diarrhoea, nosebleeds, bleeding for longer than expected from minor cuts and an unsteady gait.

Many of these overlap with other illnesses, which is why diagnosis is hard. If your dog has started coughing, our guide to why dogs cough covers the wider picture, and kennel cough is a more familiar cause.

Causes and risk factors

Blue Cross explains that dogs become infected by eating larvae in infected snails, slugs or frogs. They can also swallow tiny slugs by accident on toys, in fur or in dropped food. Infected dogs pass larvae in their faeces, which can infect more slugs and snails, but dogs don’t pass it directly to other dogs.

The PDSA says dogs that eat slugs and snails, often while eating grass, are at risk. Blue Cross says lungworm is becoming more common in parts of the UK, with cases higher in southern England and South Wales. The European parasite body ESCCAP also lists dogs that eat grass, slugs or snails as higher risk. If your dog does this a lot, our page on why dogs eat grass is worth a read.

When to call your vet

The PDSA is clear: contact your vet immediately if your dog has symptoms of lungworm. Blue Cross says the same: speak to your vet straight away. Collapse, seizures, breathing difficulty and unexplained bleeding are all on the PDSA’s list of signs, so if you see any of them, ring your practice or its out-of-hours service without delay. If you need to find a practice, use our vets database.

How vets diagnose it

Blue Cross says vets most often use a blood test alongside questions about symptoms. A faecal sample can help but is not 100 per cent reliable, and X-rays may show lung changes in more severe cases. ESCCAP describes looking for first-stage larvae in fresh faeces using the Baermann method, ideally from three consecutive samples, and notes that a commercial test for circulating antigen also exists.

What vets generally do about it

Treatment depends on how severe the infection is and what signs your dog has, and it is for your vet to decide. The PDSA says a vet kills the worms with a deworming product and monitors the dog closely, because killing many worms at once can cause a serious allergic reaction. Mild cases may only need medication at home. Severe cases may need hospital care, such as oxygen, fluids through a drip, a blood transfusion or anti-seizure medication.

Blue Cross says most dogs recover if the infection is caught and treated early, though some are left with lung scarring. The PDSA says dogs with breathing difficulty or seizures have a poorer outlook, and severe cases can be fatal.

Living with it and prevention

Prevention is the sensible route, and it is a conversation for your vet. The PDSA says there are currently no lungworm treatments available without a prescription, and shop-bought or online products that claim to help are not licensed and are often less effective. Blue Cross adds that standard pet shop wormers usually don’t cover lungworm. So ask your vet which prescription product suits your dog and how often it is needed.

Blue Cross also suggests stopping your dog from eating slugs, snails and frogs where you can, and changing the water in outdoor bowls regularly. Blue Cross says lungworm is not known to infect people. Treatment can be expensive, so our pet insurance guide is worth a look.

Related conditions

• Worms in dogs
• Kennel cough in dogs
• Heart disease in dogs
• Epilepsy and seizures in dogs
• Ticks on dogs

You can browse every condition in the dog illnesses and conditions A to Z.

Sources

• PDSA, Lungworm in Dogs
• Blue Cross, Lungworm in Dogs
• ESCCAP, Guideline 01: Worm Control in Dogs and Cats (7th edition, 2025)

This page is general information, not veterinary advice. If you are worried about your dog, speak to your vet. Written by Georgiana & Figo, who are dog owners, not vets. Have a look around Calmshops for everyday dog essentials.