Pathophysiological changes in the ruminant abomasum caused by Ostertagia
infections include changes in the activity and concentration of gastrointestinal
enzymes and
hormones. Under certain circumstances, increases in concentration also occur in the bloodstream and, as such, are detectable. Determination of serum
pepsinogen levels is useful in evaluating the risk or presence of
ostertagiasis Type I in a herd. It seems less reliable when used to diagnose (pre)
ostertagiasis in individual animals. Measurement of the concentration of other
zymogens is not useful. The variations in methodology to determine
pepsinogen levels (e.g. biochemical and immunological measurements) are discussed. Serum
gastrin levels are, generally, increased in animals with
ostertagiasis. At present,
gastrin is mainly determined by RIA assays using human
gastrin antibodies, but few baseline data are available on normal levels in ruminants. The use of
gastrin determination as a diagnostic tool in Ostertagia-infected ruminants is limited.