Testing a molasses-based bait for oral vaccination of white-tailed deer (Odocoileus virginianus) against Mycobacterium bovis

Authors: Palmer, Mitchell; Stafne, Molly; Waters, Wade; Thacker, Tyler; PHILLIPS, G - Animal And Plant Health Inspection Service (APHIS)

Submitted to: European Journal of Wildlife Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2013
Publication Date: 11/8/2013
Publication URL: http://handle.nal.usda.gov/10113/58895
Citation: Palmer, M.V., Stafne, M.R., Waters, W.R., Thacker, T.C., Phillips, G.E. 2013. Testing a molasses-based bait for oral vaccination of white-tailed deer (Odocoileus virginianus) against Mycobacterium bovis. European Journal of Wildlife Research. 60:265-270.

Interpretive Summary: White-tailed deer are wildlife reservoirs of bovine tuberculosis (TB) within the northeast region of the lower peninsula of Michigan, United States. The presence of this reservoir host seriously hinders ongoing efforts to eradicate this disease from cattle, especially in this area of the country. Control measures alternative to abattoir surveillance or test and slaughter campaigns are being considered for control in other developed countries with wildlife reservoirs of bovine tuberculosis. In particular, vaccines are being evaluated for use in the reservoir host(s) in Great Britain, Republic of Ireland, and New Zealand. In the United States, reservoir population management and test and slaughter strategies have not been successful in managing the disease in locales where the disease is endemic in the reservoir host (white-tailed deer). Thus, state and federal officials are considering a strategy to vaccinate free-ranging white-tailed deer for TB in these areas. In the present study, baits were developed for oral delivery of a tuberculosis vaccine to white-tailed deer. Physical stability, storage capacity, and palatability of the baits to deer were evaluated. The results demonstrated that molasses-based baits represent a plausible and stable means of oral delivery of tuberculosis vaccines to deer under most environmental conditions. Findings demonstrate the potential for this strategy in controlling disease within the reservoir host. These findings are useful for the tuberculosis eradication campaign within the United States.

Technical Abstract: White-tailed deer (Odocoileus virginianus) in Michigan, USA are wildlife reservoirs of bovine tuberculosis (bTB) with documented spread to cattle. In vaccine efficacy trials, Mycobacterium bovis bacillus Calmette Guerin (BCG) administered orally reduces colonization and bTB-associated lesions in white-tailed deer after experimental challenge with virulent M. bovis. The objective of this study was to develop and evaluate the palatability of a molasses-based bait for oral delivery of BCG vaccine to white-tailed deer. Additionally relevant practical aspects of the bait such as physical stability under various environmental conditions were evaluated. Captive deer consumed baits within 3 hours of introduction during 48 of 50 trials. Digital game cameras revealed consumption of all placed baits were by one deer over 62 percent of the time. Addition of BCG vaccine did not negatively impact palatability. Physical stability analysis demonstrated that ice and water significantly reduced bait stability as measured with a compression assay. Storage of BCG-containing baits at 4°C showed a slight decrease in colony forming units (CFUs) by day 31. In contrast, storage at -20°C or -80°C over the same 31 day period showed no significant decrease in BCG viability (p>0.05). The results of this study suggest molasses-based baits, as prepared here, represent a plausible and stable means of oral delivery of BCG to white-tailed deer under most environmental conditions.