Thus all the important changes associated with Ostertagiasis occur here. These larvae grow and molt twice to become immature adults. The inflammatory responses induced by growing larvae produce a constant erosion of the secretory epithelium lining the gastric glands and its replacement by an immature non-secretory epithelium. At post mortem these parasitized glands can be seen as white raised nodules on the abomasal surface. The functional consequences of these changes are fairly insignificant, at least, for now.
Infected animals eat and gain weight Plasma pepsinogen levels rise slightly.
However, in young susceptible animals on pasture for their first grazing season, significant changes are about to occur.