The Lungworm Life Cycle
Almost every lungworm relies on a stepping-stone host — usually a slug or snail. Understanding the loop is how you break it.
A cycle built around slugs and snails
Most lungworms cannot pass directly from one animal to another. Instead they depend on an intermediate host — typically a slug or snail — to develop into the infective stage. This is the central fact that makes prevention possible.
Step by step
Adult worms in the lungs
Mature lungworms live in the airways, lung tissue or nearby vessels and produce eggs or larvae.
Larvae leave the body
The animal coughs up larvae, swallows them, and passes them out in its faeces onto the ground.
Slugs & snails pick them up
Larvae are eaten by — or actively burrow into — slugs and snails, where they become infective.
The animal is infected
The host swallows an infected slug or snail (or a prey animal that ate one), or grazes contaminated pasture.
Migration to the lungs
Immature worms travel from the gut through the body to the lungs, mature, and start the cycle again.
Why the cycle matters for prevention
Because slugs and snails are the link, much of prevention comes down to limiting contact with them: picking up toys and water bowls overnight (when molluscs are active), not letting pets eat grass or drink from puddles, and on farms, managing grazing so animals aren’t turned onto heavily contaminated pasture. Regular, vet-guided worming closes the gap.
Paratenic hosts: the shortcut
Cats and some dogs often get infected indirectly, by eating frogs, birds or rodents that have themselves eaten infected slugs or snails. These “transport” hosts let the parasite reach a hunter that never touches a slug.
Treating a lungworm infection?
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