Pigs get infected with A. suum by ingesting infectious parasite eggs that are present in the environment.

[3] The larvae hatch from the egg inside the pig's intestines and subsequently start their migration through the body.

Once the larvae are inside the lung, they migrate up the respiratory tree and are eventually coughed up and swallowed by the host to reach the small intestine again as soon as 10 days after infection.

There, the larvae undergo their first molt inside the host to reach the L4 stage by day 14 post-infection.

These may include beetles and earthworms, as well as large to jumbo chicken eggs from at-risk fowl.

[citation needed] Ascaris eggs can remain infective for years in the soil, even in a temperate climate.

[5] The migration of A. suum larvae through the lungs may cause secondary bacterial infections and result in acute respiratory symptoms in pigs.

The mammillated layer is stained golden-brown by the host's bile when the eggs are passed in faeces.