Location: Infectious Bacterial Diseases Research2011 Annual Report
1a. Objectives (from AD-416)
1) Characterize the immunopathogenesis of Mycobacterium bovis infection in domestic livestock and wildlife. 2) Develop and evaluate improved tests for diagnosis of M. bovis infection in different animal species. 3) Identify vaccine strategies to elicit protective immunity in cattle and relevant wildlife species.
1b. Approach (from AD-416)
Objective 1 will evaluate tonsilar processing of M. bovis and lesion development using a combination of invitro and in vivo methods and both non-infected and experimentally infected cattle and deer. Objective 2 will utilize blood samples from both naturally and experimentally infected cattle and deer to evaluated test sensitivity as well as normal cattle and deer to evaluate test specificity. Vaccine trials in Objective 3 will be limited to efficacy studies utilizing experimentally infected animals and a combination of quantitative and semi-quantitative analysis to evaluate vaccine efficacy.
3. Progress Report
Activities within the ARS Tuberculosis (TB) Project relate to the National Program 103 Action Plan through development of tools for use in the control of bovine TB. This research is performed to provide direct support for the USDA TB eradication program. The approach is to evaluate vaccine (Objective 3) and diagnostic (Objective 2) strategies, as well as basic disease processes (i.e., immunopathogenesis studies, (Objective 1) in partnership with federal and state agencies, industry (veterinary biologics companies), and academia. Progress was made on all project objectives and include: continued discovery and validation of improved antigens for use in immune-based TB assays; characterization of immune responses of cattle to Mycobacterium Bovis (M. Bovis) infection; development of novel methods to detect determinants of infection; ultrastructural and functional characterization of tonsil lymphoid and epithelial tissues (a major portal of entry for the TB bacillus) in cattle; evaluation of M. bovis bacillus Calmette-Guerin (BCG) persistence in white-tailed deer and potential for spread to cattle; large-scale production (with National Veterinary Services Laboratory) of BCG for use in experimental and field; sequencing and comparison of whole genomes of environmental Mycobacteria spp. that potentially confound current diagnostic tests; field evaluation of serologic tests in captive cervids; and, evaluation of virulence of two M. bovis strains in cattle. In addition to supporting the mission of USDA/APHIS, these studies support stakeholder interests such as the beef, dairy, and captive cervid producers as well as state Departments of Agriculture and Natural Resources (in particular – Michigan, Colorado, Nebraska, South Dakota).
1. Demonstrated that Mycobacterium Bovis (M. Bovis) bacillus Calmette-Guerin (BCG), a live Tuberculosis (TB) vaccine, transmits from deer to deer but not from deer to cattle. These studies were performed to determine potential risks for the safety of white-tailed deer, cattle, and humans when the vaccine is used under field conditions in TB-endemic zones in Michigan, USA. We determined that: (1) M. bovis BCG persists in white-tailed deer up to 9 months after administration (however, not in muscle tissue that may be consumed by hunters); (2) BCG is clinically safe in deer, and (3) BCG may be transmitted from deer to deer, but does not transmit from deer to cattle. The impact of these findings is: (1) BCG is safe for use in white-tailed deer, and (2) BCG vaccination of free-ranging deer (e.g., in Michigan, when eventually used) will not interfere with traditional TB tests in cattle (i.e., via transmission to cattle and evoking a positive skin test response).
2. Demonstrated the usefulness of serologic tests for the detection of tuberculosis (TB) in elk and fallow deer naturally infected with Mycobacterium Bovis (M. Bovis). Skin test procedures are problematic in captive cervid species because of variable accuracy of the test and injury risks due to handling of the animals (i.e., skin test requires two handling events). With samples from a heavily infected captive elk and fallow deer herd (~70% prevalence), we demonstrated that two serum-based tests that detect TB-specific antibodies provided much improved accuracy as compared to that achieved with the skin test. In association with prior studies by our group, the collective impact is that a blood-based test is now available for use in captive cervids pending approval by United States Animal Health Association/TB committee and USDA TB program staff for official use in the eradication program.
3. Developed a new polymerase chain reaction (PCR)-based test with improved specificity for the detection of Mycobacterium Bovis (M. bovis) within tissues homogenates. These studies were performed to develop a more accurate test for the detection of M. bovis in fresh tissues. The specificity of PCR-based assays on tissue homogenates is critical since environmental Mycobacteria may be associated with tissues submitted for diagnostic tests. PCR based assays must be able to differentiate M. bovis from these environmental mycobacteria. The new test had increased specificity as compared to the currently used test. The impact is that a better test may be available for use in the tuberculosis surveillance program - pending large-scale field evaluation of test sensitivity.
Palmer, M.V., Thacker, T.C., Waters, W.R., Robbe-Austerman, S., Semakaleng, L., Harris, N.B. 2010. Persistence of Mycobacterium bovis Bacillus Calmette-Guerin (BCG) in White-tailed Deer (Odocoileus virginianus) after oral or parenteral vaccination. Zoonoses and Public Health. 57(7-8):e206-e212.