Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 11/3/2005
Citation: Hall, M.S., Richt, J.A., Davis, A.J., Levings, R.L. 2005. Where we've been and where we're going with BSE testing in the United States [abstract]. 48th Annual Meeting of the American Association of Veterinary Laboratory Diagnosticians. p. 20. Interpretive Summary:
Technical Abstract: A review of the laboratory aspects of the United States Department of Agriculture's (USDA) Bovine Spongiform Encephalopathy (BSE) Surveillance Program from its beginning to the present day will be provided. Validated diagnostic tests for BSE require brain tissue. There are no ante mortem (blood/serum) tests for BSE available at present. From a historical perspective, diagnostic tests for BSE continue to evolve. The original diagnostic test method was histopathology in which sections of brain were examined under a microscope, and the classical vacuoles and spongiform change in specific areas of the brain would allow a diagnosis to be made. This method was accurate but only allowed a diagnosis to be made relatively late in the course of the disease. In the mid-1990s, immunohistochemistry (IHC) and Western blotting were developed which allow the detection of the abnormal form of the prion protein (PrPSc) and a diagnosis could be made prior to the development of spongiform changes and clinical signs. In the past decade, so-called "rapid tests" have been introduced commercially for BSE. Five commercial tests are currently licensed/permitted in the United States for BSE. These licensed tests include the Prionics Western blot, Prionics ELISA, Enfer/Abbott ELISA, IDEXX ELISA, and the BioRad ELISA. This presentation will discuss various attributes of the validated test methods available today. Both IHC and Western blot are considered confirmatory tests for BSE by the World Organisation of Animal Health (OIE). IHC provides for a specific immunological detection of PrPSc and enables the specific anatomical location to be determined. Western blot provides both immunological detection of PrPSc as well as specific molecular weight characterizations; certain Western blot procedures can be extremely sensitive due to various concentration procedures before analysis of the sample. The OIE recommended Western blot and IHC methods for confirmatory diagnosis of BSE used by USDA and the Veterinary Laboratories Agency in Weybridge, England, will be discussed. The overall enhanced testing plan that has been used for the past 18 months will be described including changes that have occurred during this time. The USDA's BSE enhanced surveillance plan has been a very successful national surveillance testing program that has been a shared effort between state veterinary diagnostic laboratories as part of the National Animal Health Laboratory Network and the National Veterinary Services Laboratories.