Tuberculosis in White-Tailed Deer in Michigan: A Review of Three Years (1995–1997) Surveillance
Mycobacteriosis is an important re-emerging zoonotic disease. The first known occurrence of self-sustaining tuberculosis in free-ranging cervids in North America has been recognized in Michigan since the fall of 1994. In order to eradicate this disease, a multi-agency task force consisting of personnel from the MI Department of Natural Resources, MI Department of Community Health, MI Department of Agriculture, U.S. Department of Agriculture, and the Animal Health Diagnostic Laboratory was formed. While this task force has a number of ongoing responsibilities, this paper will concentrate on the techniques of surveillance, the results of the wild deer surveillance program over the last 3 years, and the management strategies employed to control this tuberculosis outbreak.
A single hunter-killed white-tailed deer (Odocoileus virginianus) was identified as having Mycobacterium bovis infection during the fall hunt of 1994. During the 1995 hunting season, 354 hunter-killed deer were examined for tuberculosis.2 These examinations consisted of gross and histologic evaluations, as well as mycobacterial isolation from cranial and thoracic lymph nodes. The estimated prevalence rate from the 1995 survey was 5.0%. Subsequently, a special deer management area was formed around the known positive deer—DMU 452—and the annual hunting season survey was expanded in 1996 to include four counties. In 1996, 3,765 deer were surveyed with an overall four-county prevalence rate of 1.24%, but a prevalence of 2.33% within DMU 452. In 1997, a fifth county, immediately north of the original four, was added into the survey. Approximately 3,700 deer were surveyed in 1997; the overall five county prevalence was 1.97%, a prevalence of 2.25% within the four-county area, and a prevalence of 4.44% within DMU 452. To date three coyotes have been found positive for tuberculosis,1 surveillance of a nearby free-ranging elk herd has been negative, all cattle tested within the five-county area have been negative, and one captive deer herd—out of approximately 30 in the five county area—has been positive for tuberculosis (Figure 1).
Since the prevalence rate has been increasing in the wild deer, and one infected captive deer herd has been identified, the tuberculosis task force will be implementing additional management strategies in 1998. The ongoing surveillance programs will continue for wild deer, wild elk, wild carnivores, captive deer, and domestic cattle in the five-county area. The entire five-county area will become a single deer management unit; within this unit increased hunting pressure will be utilized to decrease the deer herd density. Additionally, a voluntary ban on supplemental feeding of deer will be made mandatory in 1998. By decreasing deer numbers and eliminating the abnormal concentrations of deer at feeding stations it is believed that the rate of transmission of tuberculosis will dramatically decrease. Hunter education concerning the lesions of tuberculosis, as well as increased field examination of carcasses at highway deer check stations will also be continued.
1. Bruning-Fann, C.S., S.M. Schmitt, S.D. Fitzgerald, J.B. Payeur, D.L. Whipple, T.M. Cooley, T. Carlson, and P. Friedrich. Mycobacterium bovis in a coyote (Canis latrans). J. Zoo Wildl. Dis. (In press)
2. Schmitt, S.M., S.D. Fitzgerald, T.M. Cooley, C.S. Bruning-Fann, L. Sullivan, D. Berry, T. Carlson, R.B. Minnis, J.B. Payeur, and J. Sikarskie. 1997. Bovine tuberculosis in free-ranging white-tailed deer from Michigan. J. Wildl. Dis. 33:749–758.