Usda Selects Â??mad Cow’ Rapid Test that Was First Evaluated at Colorado State

One of the rapid tests that the U.S. Department of Agriculture today announced it has licensed to screen for bovine spongiform encephalopathy in cattle, known as BSE or mad cow, was first validated for use in the United States at Colorado State University’s Veterinary Diagnostic Laboratory to detect chronic wasting disease in deer and elk. The Bio-Rad rapid test was the first rapid test approved for use in the United States and is currently the only rapid test approved for all three species of deer (white tailed, mule and elk).

"We have extensive experience using the Bio-Rad rapid test and fully support USDA’s decision to use the procedure to test for BSE," said Barbara Powers, director of Colorado State’s Veterinary Diagnostic Laboratory. "The procedure for detecting BSE in cows is the same as detecting chronic wasting disease, or CWD, in wildlife, and the Bio-Rad rapid test has been proven in our laboratory to be an effective assay for quickly and accurately testing samples for CWD. European data indicates that the test is equally effective in testing for BSE."

As a result of Colorado State’s in-depth testing, in a joint effort between the university and the Colorado Division of Wildlife, the Bio-Rad rapid test was approved in late 2002 by the USDA for use nationwide in detecting CWD. Colorado State’s Diagnostic Laboratory also provided information to the USDA regarding the logistics of handling large sample volumes over short time periods during the recent BSE surveillance program review process. As a result of USDA’s enhanced BSE surveillance plan, U.S. diagnosticians will now also use the rapid test procedures and equipment to detect mad cow disease.

BSE and CWD are both transmissible spongiform encephalopathies, or TSEs, diseases that cause neurodegenerative disorders and are characterized by the accumulation of an abnormal form of the naturally occurring prion protein in the central nervous system.

Colorado State research results show that the Bio-Rad rapid test is a highly efficient procedure for diagnosing large numbers of TSE samples in a short period of time. The test takes only four to five hours to complete compared to the five days necessary for the previously used "gold standard" immunohistochemistry test, or IHC. The rapid test permits four to five times more samples to be processed in a single day. Because of the increased efficiency, over the past 18 months the Colorado State laboratory has screened nearly 47,000 deer and elk with the rapid test system compared to the approximate 40,000 they were able to do over the last four years with the IHC test.

"IHC is a costly, labor-intensive and time-consuming technique necessitating several histology technicians and pathologists to diagnose samples," said Powers. "The Bio-Rad rapid test is designed for large-volume sample screening and is a very effective and practical solution to meet increased demand for TSE testing and surveillance. It is faster, requires fewer personnel, allows for automation and larger daily volumes of samples is less expensive, and is extremely accurate."

The Bio-Rad rapid test is designed to run on a robotic system that automates a portion of the testing procedure, speeds up sample preparation and enables laboratories to provide faster results using fewer technicians. Colorado State’s Veterinary Diagnostic Laboratory was the first laboratory in the world to use the new robotic system to screen CWD samples.

"With the automated system, we are usually able to provide results within 24 hours after we receive samples," said Powers.

The rapid test originally performed well in field validation trials at Colorado State on more than 25,000 CWD samples, successfully identifying all positive animals. For the initial validation phase, Veterinary Diagnostic Laboratory researchers examined more than 4,000 samples independently by the rapid test and IHC; overall agreement between the two tests was nearly 100 percent for lymph nodes. Based on these results, the rapid test to detect CWD in deer and elk was granted a license by the USDA for nationwide use in November 2002.

For the second phase, more than 20,000 lymph nodes were analyzed. For this phase, the immunohistochemistry test was only used to confirm positive rapid test results. The rapid test proved to be equally as sensitive, specific and reliable in the larger field application as in the validation tests for diagnosing brain and lymphoid tissue samples.

Based on these positive results, Colorado State used the rapid test as its standard operation to evaluate nearly 17,000 hunter-submitted samples of elk and deer for CWD in the state for the 2003-2004 hunting season. Each of the samples that tested positive also was tested with the IHC test that confirmed the positive Bio-Rad test results, the same procedure that will be used by USDA if any positive BSE samples are found.

Colorado State University’s Veterinary Diagnostic Laboratory System’s responsibilities include monitoring and testing for animal diseases. The laboratory is part of both of USDA’s two networks of laboratories: the TSE contract laboratory network of 26 USDA inspected laboratories and the National Animal Health Laboratory Network of 12 laboratories. The Colorado State laboratory also is accredited by the American Association of Veterinary Laboratory Diagnosticians as a full-service laboratory for all species of animals.