Evaluation of the influence of supplemental feeding of white-tailed deer (Odocoileus virginianus) on the prevalence of bovine tuberculosis in the Michigan wild deer population

A retrospective study was conducted to test the hypothesis that supplemental feeding of white-tailed deer (Odocoileus virginianus) from 1995 to 1997 was associated with the prevalence of bovine tuberculosis (TB) in free-ranging deer in northeastern Michigan. Bovine TB prevalence data were obtained from an ongoing surveillance program, while data relating to supplemental feeding and other risk factors were collected via in-person interviews. A multivariable Poisson regression modeling approach was used to test the stated hypothesis while controlling for other risk factors. Of the 389 potential participants, 59% agreed to participate in the study. Results showed that supplemental feeding of deer was associated with bovine TB in white-tailed deer. Specific risk factors associated with increasing risk for bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=1.8, 95% C.I.=1.3-2.4), other large-scale feeding sites in the area (O.R.=1.1, 95% C.I.=1.0-1.2), the number of deer fed per year (O.R.=3.9, 95% C.I.=1.4-11.4), the numbers of feed sites spreading grain (O.R.=14.7, 95% C.I.=2.2-98.9), the quantity of grains provided at the site (O.R.=1.4, 95% C. I.=1.1-1.7), and the quantity of fruits and vegetables provided (O.R.=1.4, 95% C.I.=1.2-1.7). Conversely, factors associated with decreasing risk of bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=0.1, 95% C.I.=0.02-0.4), locating feed sites in forests (O.R.=0.05, 95% C.I.=0.01-0.4), and the level of sites providing grain (O.R.=0.1, 95% C.I.=0.01-0.3). The results of this study suggest that banning the practice of supplemental feeding is a valid policy for control of bovine tuberculosis in free-ranging white-tailed deer.