The preparasitic phase of Oesophagostomum is typically strongyloid, and
infection is by ingestion of L3s.
() The L3s
exsheath in the small intestine then enter the mucosa of any part of the small or large
intestines. In some species (Oe. columbianum, Oe. quadrispinulatum and Oe. radiatum)
L3s become enclosed in obvious nodules in which they moult to L4s . These L4s then
emerge on to the mucosal surface, migrate to the colon (A),
and develop to the adult stage.
The prepatent period is 32 to 45 days, depending on the species. On reinfection
with most species, the larvae may remain arrested as L4s, in nodules, for up to one year.