Dogs become infected with Aelurostrongylus abstrusus by ingesting intermediate hosts such as snails or paratenic (paratenic describes an intermediate host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite) hosts (birds, rodents etc).

After ingestion, the larvae pass into the intestine. The larvae penetrate intestine wall and migrate to the lungs in the blood, once they have matured to adult worms (approx 40 days) they lay eggs, these hatch into microscopic larvae which are coughed up, swallowed & passed in the faeces.