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Researchers Develop Better Tests for Bacterial Diseases in Cattle



(NAFB)--USDA Agricultural Research Service scientists at the National Animal Disease Center in Iowa are looking for ways to help control bovine tuberculosis and Johne’s disease - both caused by mycobacteria - by developing and improving diagnostic tests, vaccines and other technology.

NADC Veterinary Medical Officer Mitch Palmer says the diagnostic tuberculin skin test for cattle has helped slow the spread of bovine TB - but it’s not sensitive enough - and may not be able to detect all TB-positive animals in a large herd. In most cases - Palmer says the entire herd is euthanized when one animal is infected with TB. Palmer and the other scientists are working toward a better test to allow producers to identify and remove infected cattle - keeping TB-free animals.

Already these scientists have developed a new serum TB diagnostic test from discovering a certain antigen is useful in bovine TB antibody-based tests. Scientists say the test is more convenient and could be used with other tests to identify TB-infected animals that may have gone undetected. NADC Microbiologist Tyler Thacker has created another test based on polymerase chain reaction analysis of DNA - or PCR. This test can detect the disease in fresh tissues and is much faster than a traditional PCR assay.

As for Johne’s Disease - Microbiologist John Bannantine has discovered an antibody that is 100-percent specific in detecting MAP - the pathogen that causes Johne’s Disease. Vaccines can reduce the severity of this disease - but they cannot cross-react with tests for other diseases. Scientists have studied the cross-reactivity of Johne’s vaccines and TB tests - and no reactivity was found using TB tests with vaccinated calves - meaning the tests won’t wrongly identify cattle with Johne’s disease as positive for bovine TB

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