How Do Lungworms Affect Dogs?

Lungworms are parasitic nematodes that inhabit the respiratory tract of dogs, and whilst they're less commonly discussed than intestinal worms, they pose a genuine health threat to our canine companions. Unlike their intestinal cousins, lungworms can cause chronic coughing, breathing difficulties, and in severe cases, life-threatening complications. Understanding how these parasites affect dogs is essential for early detection and effective treatment.

What Are Lungworms and How Dogs Get Infected?

Lungworms are parasitic worms that live in the lungs and airways of infected dogs. The most common species affecting UK dogs is Angiostrongylus vasorum, also known as the French heartworm, though it's found throughout Europe.

Dogs typically contract lungworms by ingesting infected intermediate hosts, including:

Slugs and snails (the primary source)
Frogs and toads
Small rodents that have consumed infected slugs
Contaminated water or vegetation

Many dogs pick up infections whilst playing outdoors, drinking from puddles, or eating grass contaminated with slug slime—a common behaviour that puts them at particular risk.

Signs and Symptoms of Lungworm Infection

Lungworm symptoms can be subtle initially, making early diagnosis challenging. Watch for these warning signs:

Persistent cough, often described as a "reverse sneeze"
Lethargy and reduced exercise tolerance
Laboured or rapid breathing
Loss of appetite and weight loss
Wheezing or respiratory distress
Bleeding from the nose or mouth (in severe cases)
Pale gums indicating anaemia
Reluctance to play or exercise

Symptoms typically appear two to four weeks after infection, though some dogs remain asymptomatic whilst harbouring the parasites.

Serious Complications of Untreated Lungworm

If left untreated, lungworm infections can progress to serious conditions:

Pneumonia: Secondary bacterial infections in damaged airways
Pulmonary haemorrhage: Bleeding into the lungs
Coagulopathy: Blood clotting disorders affecting the entire body
Cardiovascular complications: Including heart arrhythmias and heart failure
Neurological issues: Rarely, parasites can migrate to the brain

In worst-case scenarios, severe untreated infections can be fatal, which is why prompt veterinary attention is crucial.

Diagnosis and Treatment Options

Your vet can diagnose lungworm through several methods:

Faecal examination to identify parasite larvae
Blood tests showing antibodies or altered blood counts
X-rays revealing lung abnormalities
Bronchoscopy (in complex cases)

Treatment typically involves anthelmintic medications prescribed by your veterinarian. Most dogs respond well to targeted antiparasitic drugs, though treatment duration varies depending on infection severity. Your vet may also prescribe supportive care such as antibiotics for secondary infections or anti-inflammatory medications.

Prevention Strategies

Prevention is far more effective than treatment. Implement these practical measures:

Use monthly parasite preventatives recommended by your vet—many modern spot-on treatments and tablets protect against lungworms
Discourage your dog from eating slugs, snails, or scavenging outdoors
Provide fresh, clean drinking water instead of allowing puddle drinking
Maintain good garden hygiene and remove visible slugs and snails
Consider keeping your garden less hospitable to slugs by reducing damp areas

Key Takeaways

Lungworms are serious parasites that require prompt veterinary attention. By recognising early symptoms, maintaining regular preventative treatments, and discouraging outdoor scavenging behaviours, you can protect your dog from this potentially life-threatening condition. If your dog shows any respiratory symptoms or has access to areas with slugs and snails, discuss lungworm protection with your vet at your next appointment.