The preparasitic phase of this life cycle is virtually identical to that of Strongylus vulgaris described previously . Of the three large strongyles, we know the least about the parasitic phase of the life cycle of Strongylus equinus because it is less common than the others and so has been little studied.
Infection is by ingestion of third stage larvae and exsheathment occurs in the small intestine.
L3s invade the wall of the small intestine, cecum and colon and become encapsulated in nodules in which they molt to L4s by 12-14 days after infection. L4s leave their nodules and cross the peritoneal cavity to the liver, the right lobe of which is in close aposition to the cecum. Most L4s will have reached the liver by 19-20 days after infection and will remain there for at least 12 weeks. L5s penetrate the gut wall and enter the lumen of the large intestine via the formation of nodules. Reproduction takes place and the prepatent period is approximately 9 months.