Lungworm in Dogs UK — Angiostrongylus Vasorum Symptoms & Prevention

According to the BVA and PDSA, lungworm in UK dogs is caused by the parasite Angiostrongylus vasorum. Unlike intestinal worms, lungworm lives in the heart and major blood vessels of the lungs, causing bleeding and respiratory disease.

The parasite was once considered a southern England problem but has spread widely. Cases are now reported across England, Wales, Scotland, and parts of Northern Ireland. Any dog that explores gardens, parks, or countryside can be exposed.

Lungworm is not contagious between dogs directly. Infection requires ingesting the intermediate hosts — slugs, snails, or their slime — or frogs that have ingested larvae.

Dogs cannot get lungworm from dry slug pellets — that is a separate poison risk — see slug pellet poisoning. Lungworm transmission works like this:

1. Slugs and snails carry lungworm larvae
2. Dogs eat the mollusc or lick slime trails on grass, pavements, toys, or water bowls
3. Larvae migrate through the body to the heart and pulmonary arteries
4. Adult worms produce larvae that pass in faeces — slugs eat faeces, continuing the cycle

High-risk behaviours:

• Eating slugs and snails deliberately
• Chewing grass where slugs have crawled
• Playing with outdoor toys and bowls left in the garden overnight
• Drinking from puddles and outdoor water sources
• Puppies exploring with their mouths

Even small slugs and invisible slime trails can carry enough larvae to cause disease.

Signs vary from mild to life-threatening. Some dogs show few early symptoms while worms cause progressive damage.

Respiratory signs

• Coughing — persistent or intermittent — see why is my dog coughing
• Breathing difficulty and exercise intolerance
• Lethargy after walks that used to be easy

Bleeding disorders

Lungworm damages blood clotting. Warning signs include:

• Nosebleeds or blood from the mouth
• Pale gums and weakness — anaemia
• Unexplained bruising on skin or gums
• Prolonged bleeding from minor wounds
• Blood in urine or faeces

Bleeding can be sudden and severe — a life-threatening emergency.

Neurological signs

In some cases, larvae migrate to the spinal cord or brain, causing:

• Weakness or paralysis of hind legs
• Seizures
• Head tilt and balance problems
• Collapse

General signs

• Weight loss despite good appetite
• Vomiting and diarrhoea
• Reduced appetite
• General failure to thrive in puppies

Chronic low-grade infection may mimic other conditions — arthritis, kennel cough, or heart disease — delaying diagnosis.

Your vet diagnoses lungworm through:

• History — slug access, outdoor lifestyle, geographic area
• Clinical signs — especially bleeding with respiratory signs
• Faecal tests — larvae detection (may need repeat samples)
• Blood tests — clotting abnormalities and antibody tests
• X-rays or ultrasound — lung and heart changes in advanced cases

Treatment uses vet-prescribed antiparasitic medication — typically fenbendazole or milbemycin-based products at treatment doses. Severe cases need hospital care:

• Oxygen therapy for breathing difficulty
• Blood transfusions for severe anaemia
• IV fluids and supportive care
• Cage rest during recovery

Early treatment improves outcomes. Delayed diagnosis — especially when bleeding is advanced — carries higher mortality.

According to the BVA and Blue Cross, prevention is far safer than treatment. Not all wormers cover lungworm — many supermarket products only treat roundworm and tapeworm.

Effective prevention requires monthly vet-prescribed products containing milbemycin oxime, moxidectin, or similar agents licensed for lungworm. Your vet selects products based on:

• Local endemic risk
• Your dog's weight and age
• Other parasites needing cover (fleas, ticks, intestinal worms)
• Health status and concurrent medications

See our complete guide: dog worming schedule UK.

Puppies can start lungworm prevention from the first worming visits — coordinate with puppy care UK schedules.

Prevention beyond medication

• Bring toys and bowls indoors overnight — slugs crawl on them in darkness
• Wash outdoor bowls before refilling
• Supervise puppies in gardens — slugs hide under leaves and pots
• Avoid slug pellets — metaldehyde poisoning kills dogs; use pet-safe slug control
• Check parasite prevention for pets UK for integrated flea, tick, and worm plans

You cannot eliminate every slug from a UK garden. Monthly prevention is the reliable strategy.

If your dog coughs with bleeding or bruising, mention lungworm specifically to your vet.

Angiostrongylus vasorum affects dogs and foxes — not humans. However, other slugs and snails carry French heartworm (Angiostrongylus cantonensis) rarely in the UK context. The main human message is pet protection, not owner infection from dog lungworm.

Roundworm from dogs is zoonotic — another reason for regular worming — see dog worming schedule UK.