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Easy, Inexpensive Test Detects Tuberculosis in Livestock and Wildlife

By Luis Pons
November 21, 2002

A test developed by Agricultural Research Service scientists for detecting bovine tuberculosis may not only be revolutionary, but very timely as well.

The breakthrough--a new blood-based assay for detecting the disease in animals--is important because it is applicable for most if not all species of mammals and requires only a single blood sample. That means animals are handled just once.

A patent application for the test has been submitted by the U.S. Department of Agriculture on behalf of the inventors, veterinarians Ray Waters and Mitch Palmer. They work in the Bacterial Diseases of Livestock Research Unit at ARS' National Animal Disease Center in Ames, Iowa. ARS is the USDA's chief scientific research agency.

The assay detects nitrite--as an indication of nitric oxide production--in blood-sample cultures. Mammals produce nitric oxide as a natural response when fighting tuberculosis.

According to Waters, the test is an inexpensive and easy process for diagnostic laboratories and regulatory agencies. It will likely be used on livestock species such as cattle, sheep and goats and on wildlife such as deer, bison and elk.

Currently, the only government-approved tuberculosis-detection method is a skin test that causes a reaction that is measured 72 hours later. Handling the animal a second time can lead to injury and stress, especially to wildlife species, according to Waters.

Eradication efforts started by the USDA in 1917 almost eliminated bovine tuberculosis. But recent developments, including outbreaks among white-tailed deer in Michigan and feeder cattle in Texas, show that the disease is still active in the United States.

The new, still-unnamed test can detect all three types of tuberculosis--human, avian, and bovine--according to Palmer. He notes that another test, an interferon gamma assay already in use for livestock, is based upon the same blood-culture principle as their procedure. However, it can't be used on other species and can only be applied in conjunction with the skin test.

Read more about this new test in the November issue of Agricultural Research magazine.