USDA researchers look to erridicate Bovine TB worldwide

USDA scientists with the Agricultural Research Service are striving to improve tests and vaccination methods to overcome obstacles that prevent the eradication of bovine tuberculosis in cattle. At the National Animal Disease Center in Ames, Iowa - scientists are developing better tests to help producers identify and remove TB-infected cattle from herds and keep healthy animals. Veterinary Medical Officer Ray Waters says the tuberculin cattle skin test has helped eradication efforts - but has drawbacks - like a 72-hour waiting period for results. Interferon-gamma release tests require live white blood cells that must be processed quickly. Waters says traditional serum tests would be more convenient and less expensive. Scientists have demonstrated that improved antigens - substances that cause the immune system to produce antibodies against foreign bacteria - are crucial in developing effective serum tests. The findings were instrumental in the recent development of a new serum TB test. Microbiologist Tyler Thacker - also collaborating on this effort at USDA - has developed another type of test based on polymerase chain reaction analysis of DNA. This new test detects the causative agent of bovine TB in fresh tissues. USDA says the test is quicker, accurate and helps distinguish between the causative agent of bovine TB and environmental mycobacteria that can cause false-positive results.

Scientists have also tested a century-old TB vaccine in deer. Colleagues fed a Bacillus Calmette-Guerin oral bait vaccine to captive deer and examined them one to 12 months later to determine how long the vaccine remained in the deer. BCG wasn't detected in the deer given a standard dose - but those receiving elevated doses - 10 times the standard - had traces of BCG in lymph nodes and other tissues not commonly used for food. The vaccine was never found in common cuts of deer meat in any of the safety experiments.

More on this research is available in the September 2013 issue of Agricultural Research magazine - which can be found on the ARS website at www dot ars dot usda dot gov (www.ars.usda.gov).

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