Ostertagia ostertagi and Cooperia oncophora are widely distributed and are the most important parasites affecting young bovine livestock. Therefore, there is a substantial need for sensitive and specific parameters in support of their diagnosis, especially for sub-clinical disease correlated to production loss. In this review, the value and the application as a diagnostic tool of
pepsinogen,
gastrin and antibody response are discussed. An increase in
pepsinogen or
gastrin reflects mucosal damage caused by an Ostertagia
infection. Some controversy exists about the level of
pepsinogen and
gastrin, which may be considered indicative for the diagnosis of clinical and sub-clinical
ostertagiasis.
Pepsinogen levels between 3,000 tot 4,000 mU
tyrosine are regarded indicative for subclinical disease, values in excess of 5,000 mU
tyrosine are considered significant for diagnosing clinical disease. For
gastrin, it is suggested that based on group means, values of 400 pg/ml are indicative for subclinical
parasitic disease in calves with reduced daily
weight gain, while threshold levels of > or = 1000 pg/ml
gastrin are representative for clinical
ostertagiasis. Antibody responses to Ostertagia and Cooperia can be assessed using the
enzyme immunoassay (EIA). Until now, mainly crude worm extracts have been used as
antigen source in the EIA. They are not species-specific as discussed experiments provide evidence of a close relationship between the onset of
parasitic disease and the evolution of the group mean parameters. However, data demonstrate serious variations between animals, which impede a reliable individual diagnosis. For longitudinal epidemiological studies especially
pepsinogen and
gastrin have proven their value, exhibiting fast fluctuations induced by
infection or as a result of treatment. Conversely antibody levels were found to be more stable and therefore are useful in large cross-sectional studies, enabling a rough assessment of the degree of
infection.