June 1, 2009 Agricultural Research Service (ARS) scientists at the National Animal Disease Center (NADC) in Ames, Iowa, are in a longstanding battle against two serious bacterial infections of livestock: Johne's disease and bovine tuberculosis.
Experts believe that almost 70 percent of U.S. cattle herds are infected with M. avium subspecies paratuberculosis (MAP), the bacterium that causes Johne's disease. NADC microbiologist John Bannantine and colleagues took information from the MAP genome to assemble an array of 96 proteins. Then they used the array to identify gene sequences that might be useful in confirming a Johne's disease diagnosis, or that might serve as targets for disease intervention and treatment.
Bannantine's team found three proteins that consistently drew the strongest "attacks" from serum antibodies, an immune response that clearly linked the three proteins with the onset of the disease. With additional work, these antigens might provide crucial building blocks for the development of a diagnostic tool for Johne's disease.
Meanwhile, NADC microbiologist Judy Stabel has been studying the early stages of MAP infection and finding ways to diagnose the disease in young animals. She has also helped evaluate animal models for MAP research, and has concluded that a smaller ruminant model-such as goats or sheep-shows promise.
NADC veterinary officers Ray Waters and Mitch Palmer and molecular biologist Tyler Thacker are working on several fronts to optimize bovine tuberculosis diagnostic tests and vaccinations for both wildlife and domestic livestock. For instance, Palmer is using white-tailed deer, which are a significant reservoir of bovine tuberculosis, to test experimental vaccines for potential bovine tuberculosis control in wildlife.
So far his studies indicate that vaccines can be effective in decreasing the severity of the disease, and that oral vaccination appears to be as effective as subcutaneous vaccination. But other safety issues still need to be resolved before the vaccine could be used in wildlife.
The NADC scientists have also been using neonatal calves to test human tuberculosis vaccines. This approach is cheaper and safer to use than testing in nonhuman primates.
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