Surveillance of BSE

The current method used to identify suspect BSE cases is based on reporting cattle displaying clinical signs compatible with BSE. The reporting of suc h cases is dependent on the ability of farmers and veterinarians to recogni se the disease symptoms and on the willingness to report such cases. Furthe rmore, it depends on the stage of the disease, because early clinical signs of BSE are not always typical. Histology and immunohistochemistry are established and reliable to confirm BSE in cattle, but the procedure is cumbersome, time consuming and therefor e not suited for mass testing of animals. A targeted surveillance system using the Prionics-Western-Blot Test was ini tiated in Switzerland in 1999. Prionics-positive results are confirmed by h istology or immunohistochemistry by the BSE-reference laboratory. This surv eillance scheme has confirmed fallen stock and cows subjected to emergency slaughter as the major risk groups. Currently all cattle from these two cat egories are tested. As a further measure a random sample of cows from regul ar slaughtering is tested. This enables to determine the BSE status indepen dent of the inaccuracies of a clinical case reporting system. This approach may be helpful to reliably assess the BSE situation in countries with low incidence in order to verify their BSE status and in countries which want t o prove their BSE-free status.