By several routes, they migrate to the veins of the intestine and liver where they mature. A bulkier male worm mates with the very slender and petite female. She then moves into smaller and smaller veins and lays her eggs and then leaves. The contractions of the vessels and intestine actually push the eggs through the wall of the vessel, the wall of the intestine, and into the intestine's lumen. The eggs are then passed in the feces.
Inflammation occurs at the site where the infective form enters.
An intense inflammation occurs in the intestine as the eggs pass through it. Diarrhea, with mucous and often blood, results. Dogs lose their appetite and may become emaciated. The wall of the intestine may become very thickened. Cirrhosis of the liver can occur if the eggs are laid in its small veins and then enter the liver itself.