In response to the discovery of an imported cow confirmed positive for bovine spongiform encephalopathy on December 25, 2003, the USDA developed an enhanced surveillance program in an attempt to accurately determine the incidence of BSE in the United States cattle population.  The enhanced surveillance began on June 1, 2004. 

 In this program, USDA officials targeted cattle from high risk categories for BSE testing.  High risk cattle are those that are condemned at slaughter for abnormal central nervous system (CNS) signs, cattle found dead without a known cause, cattle euthanized for lameness or injury without a known cause, cattle that died with signs of incoordination or severe depression. In addition, samples collected must have originated from a cow that was 30 months of age or older.

 Between June 1, 2004 and March 17, 2006, 647,045 samples were collected from 5,776 unique locations across the United States. These locations included slaughter facilities, rendering facilities and animal disease diagnostic laboratories. Of these 647,045 samples, two were confirmed positive for BSE (0.0003 percent of the test population).

 The data collected from the enhanced surveillance program will be used to develop a BSE maintenance surveillance plan for the United States that conforms with the World Organization for Animal Health (OIE) standards. The OIE is an international organization with 167 member countries that establishes animal health standards and facilitates world trade in animals and animal products. The data collected by the USDA will also be used to increase the sensitivity and representativeness of the maintenance surveillance testing program. This data will also be used to calculate the probable prevalence of BSE in the United States.

 Information in this section from USDA-APHIS Summary of Enhanced BSE Surveillance in the United States

On April 27, 2004, Agriculture Secretary, Ann Veneman, announced the framework for implementation of a National Animal Identification System (NAIS) designed to identify any agricultural premise exposed to a foreign animal disease so that control measures can be more quickly and efficiently implemented. The goal of the NAIS is to identify all animals and premises that have had contact with an emerging or foreign animal disease of concern within 48 hours.

The National Animal Identification System will support the following species and/or industries on a voluntary basis:  bison, beef cattle, dairy cattle, swine, sheep, goats, camelids (alpacas and llamas), horses, cervids (deer and elk), poultry (eight species including game birds), and aquaculture (eleven species). The first phase of the NAIS is premises indentification.  The goal of this phase is to provide more timely gathering of data in response to animal diseases. As of March 2006, 235,000 premises across all fifty states, five tribes and two territories were registered. The current goal of the NAIS is to have all of the estimated 2 million livestock premises registered by January 2009.

The second phase of the NAIS is individual animal identification. The goal is to have each animal assigned a unique number that will link it to its premises of origin.  This unique identification will allow officials to rapidly identify other animals from the same premises that may also be infected. In this manner, epidemiologic investigations will have a starting point. This phase of the NAIS began in March 2006.

The third phase of the NAIS is the creation and maintenance of animal tracking databases. These databases will maintain records on the movement of each animal into a premises and the other animals it had contact with.  The integration of this phase is targeted for 2007.

Resources:

NAIS website - USDA-APHIS

Currently, premises registration with the National Animal Identification System is voluntary.  However, premises registration is an important step in protecting our herds and food supply. Please click on your state to access NAIS online premises information and registration forms.

BSE Rapid Screening Tests: Testing cattle for BSE is dependent on detecting an abnormal prion protein in specific areas of the central nervous system.  These screening tests are utilized by USDA and Food Safety and Inspection Service (FSIS) officials to determine if an animal is suspected positive for BSE. In the event of a positive or inconclusive test, the animal's meat will either be condemned or quarantined until a confirmed result is obtained.

BSE Confirmatory Tests: If a positive or inconclusive result is obtained from the BSE rapid screening test, the sample is sent to the National Veterinary Service Laboratories for confirmation. There are two types of tests considered confirmatory for BSE: Immunohistochemistry (IHC) and Western blot.

In the IHC test, a portion of the intact brain is visually examined to determine the presence of holes or a spongy appearance.  The portion of brain will then treated with a special stain to determine the presence of abnormal prion proteins that indicate BSE. 

In the Western blot, the brain sample is exposed to a protease enzyme that will destroy any normal prion proteins in the sample leaving only abnormal prion proteins.  The sample is run through a gel which will separate the prion protein components by molecular weight. The proteins are then treated with a special stain to determine the presence of BSE prions.  Diagnosis of BSE is made when three distinctive staining bands are present. 

For more information about BSE confirmatory testing, visit the APHIS Factsheet.

National Animal Health Laboratory Network: This laboratory network was developed in 2002 as a way to improve the testing and surveillance of domestic animal diseases, such as BSE, that are a potential threat to animal and public health and the national economy. For more information and resources on this topic, please visit EDEN's NAHLN page.