Screening tests for animal TSE: present and future

In 1999, three rapid tests (Prionics, Bio-Rad, Enfer) have been validated by the European Commission for the post-mortem diagnosis of BSE in cattle. They are now used on a large scale over the entire Europe. In absence of antibodies specifically recognizing the native conformation PrPres, its selective determination is based on the biochemical properties of this abnormal form (PK resistance, aggregation in presence of detergents). In addition, all these tests include a denaturation step so that PrP can be detected by appropriate antibodies. When applied on "risk populations" or on "healthy animals" entering into the human food chain, these rapid tests have provided a better estimation of the epizootic and allowed an efficient removal of animals bearing a risk for human consumption. Since 2002, they have also been used for the post-mortem diagnosis of scrapie in sheep and goat. Five new tests have been recently evaluated (ID-Lelystad; Perkin-elmer, Prionics Check LIA, UCSF, Imperial college) but it is too early to know which place they will take in the field. Current tests allow a preclinical diagnosis of TSE, especially in sheep and goats for which a very early detection is possible in peripheral lymphoid tissues. However, to date, no test on living animal has been validated. Taking into account the important number of research teams now involved on this topic one may expect spectacular progress in the forthcoming years.