In each U.S. case, detection of unusual BSE occurred through routine screening programs for classical BSE. The two cases discovered in the United States were a result of the surveillance program administered by the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS).
Unusual BSE can be detected by ELISA, Western Blot and immunohistochemistry, which are also used for detection of classical BSE. Each detects the specific disease-causing abnormal form of the prion protein, PrPSc, but by different methodology. Because the molecular fingerprint of each form of BSE (L-type, H-type, classical) is distinct, the Western Blot technique (allows for the determination of molecular characteristics) is considered the best testing method to distinguish between these different forms of BSE.