Bovine Tuberculosis in Indiana Deer
Results of bovine tuberculosis testing
History of bovine tuberculosis
Bovine tuberculosis was eradicated from Indiana in 1984. However, in 2008, bovine tuberculosis was identified in a cow in Franklin County, and several months later in a nearby captive cervid herd of red deer, elk and fallow deer. As a result, the DNR, the Indiana State Board of Animal Health (BOAH), and USDA APHIS Wildlife Services and Veterinary Services began a voluntary hunter-harvest surveillance program in Franklin County to determine if bovine tuberculosis had spilled over into wild white-tailed deer. In 2011, bovine tuberculosis was detected in a Dearborn County cattle farm. Later that year, surveillance of white-tailed deer was expanded to include southern Fayette, Franklin and Dearborn counties. From 2009-2015, 1,415 wild white-tailed deer from this area were tested and were negative for bovine tuberculosis.
In April 2016, bovine tuberculosis was detected by BOAH and USDA on a cattle farm consisting of two premises in Franklin County. Wild animals were removed and tested from the affected areas, including 20 deer. Sixteen of the 20 deer were tested for bovine tuberculosis, and in August 2016, one deer tested positive for the disease along with one raccoon. In December 2016, a third cattle farm in Franklin County also tested positive for bovine tuberculosis. Genetic testing at the USDA APHIS National Veterinary Services Laboratory (NVSL) has shown that all of the deer species and cattle infected with bovine tuberculosis in Indiana have been affected by the same strain, indicating a single source of infection.
Current data suggest that bovine tuberculosis has possibly been circulating at extremely low levels in the deer herd since at least late 2008 when the first case was detected. Based on these findings, the DNR initiated a more intense bovine tuberculosis surveillance program during the 2016 deer hunting season in southern Fayette, Franklin and Dearborn counties.
Figure 1. Locations of cattle and cervid farms affected by bovine tuberculosis in Franklin and Dearborn counties, Indiana 2009 to 2016.
2016 bovine tuberculosis surveillance
During the 2016 hunting season, the DNR’s goal was to test approximately 2,000 hunter-harvested deer for bovine tuberculosis, with a large proportion of the animals being bucks greater than 2.5 years old because of their higher value for disease surveillance. The objectives were to: 1) determine the apparent prevalence rate of bovine tuberculosis in southern Fayette and Franklin counties within a 10-mile radius of the 2016 affected farm where the first wild white-tailed deer tested positive; and 2) detect the disease at a low prevalence level within a 10-mile radius of the 2011 affected farm in Dearborn County. At the end of the 2016 deer hunting season, 2,044 samples were collected and submitted to the Animal Disease Diagnostic Lab (ADDL) at Purdue University and to the NVSL in Ames, Iowa. All the hunter-harvested deer tested negative for bovine tuberculosis.
Calculating apparent prevalence
Because only a sample of the deer population in Franklin County were tested for bovine tuberculosis, we calculated the apparent prevalence rate of bovine tuberculosis for the surveillance zone, which is a best-estimate of the true prevalence (actual number of deer infected) of bovine tuberculosis in the wild deer population. True prevalence is only achieved by sampling every deer in the population, which is impossible in free-ranging white-tailed deer
To calculate the apparent prevalence, we used the values determined by APHIS Wildlife and Veterinary Services scientists in Fort Collins, Colo., for the Cervid Sample Size Calculator to “discount” deer based on their age and sex (males and females less than 2 years old = 1/9 of bucks greater than 2 years old; females at least 2 years old = 1/3 of bucks at least 2 years old) and how the sample was collected (hunter harvested sample = 0.75; hunter harvested sample with a chest cavity inspection = 0.80; and a deer with a full necropsy = 0.85).
10-mile zone in southern Fayette and Franklin counties
A total of 938 hunter-harvested deer and 16 targeted deer (taken in July 2016) were tested within a 10-mile radius of the location where the first infected wild white-tailed deer was found in Franklin County. Samples consisted of 241 deer less than 2 years old, 189 female deer at least 2 years old, and 524 male deer 2 years of age and older. Only one wild white-tailed deer, the wild white-tailed deer removed from the bovine tuberculosis affected farm in northern Franklin County, was positive for bovine tuberculosis.
Adjusting the number of deer using the Cervid Sample Size Calculator, we sampled an equivalent of 473 deer within the 10-mile radius, resulting in a bovine tuberculosis apparent prevalence rate of 0.21 percent at a 95 percent confidence interval. This is the best estimate of the true prevalence of bovine tuberculosis infected deer in the wild deer population in the south Fayette and Franklin counties 10-mile radius sampling area.
The only way to further refine this number is through additional sampling of deer in future years. The DNR asks for continued support of hunters that hunt within 3 miles of the 2016 bovine tuberculosis affected farms to submit harvested deer for bovine tuberculosis testing in future deer seasons.
10-mile zone in Dearborn County
We tested 836 hunter-harvested deer within a 10-mile radius of the 2011 bovine tuberculosis positive farm in Dearborn County. The surveillance was comprised of 217 yearlings and fawns, 166 does that were at least 2 years old, and 453 bucks that were at least 2 years old. All deer sampled tested negative for bovine tuberculosis. At this level of surveillance, we did not detect the disease assuming a 0.25 percent prevalence rate at a 95 percent confidence level. This means the level of bovine tuberculosis in the population is too low to detect at current sampling levels.
Figure 2. Number of hunter harvested deer sampled per square mile for bovine tuberculosis in Fayette, Franklin and Dearborn counties during the 2016 Indiana deer hunting season.
Authorizations to take an additional buck
During the 2016 bovine tuberculosis surveillance effort, the DNR offered an incentive for hunters to submit mature bucks for bovine tuberculosis testing. Hunters who harvested a buck at least 2 years old in the surveillance area and submitted it for bovine tuberculosis testing were eligible to receive an Authorization to Take an Additional Buck. The hunter’s second buck also had to be at least 2 years old, taken from the surveillance area, and submitted for bovine tuberculosis testing. IDNR issued 819 additional buck tags to hunters and 113 (13.8 percent) of these hunters were successful in harvesting a second mature buck.
The Authorizations to Take an Additional Buck had minimal impact on the deer harvest of Franklin, Fayette, and Dearborn counties. The number of bucks harvested in Franklin and Fayette counties increased by 85 antlered deer (7.7 percent) and 27 antlered deer (6 percent), respectively, from the number of bucks harvested in 2015. The antlered harvest in Dearborn County increased by only 10 bucks (less than 1 percent). The increase in bucks harvested in Franklin County was offset by a decrease in antlerless deer harvested by 266 antlerless deer (14.8 percent) from the number of antlerless deer harvested in 2015. Also, 205 fewer antlerless deer (13.8 percent) were harvested in Dearborn County compared to 2015. Eighteen more antlerless deer (2.8 percent) were harvested in Fayette County in 2016 than in 2015. The total number of deer harvested in Franklin and Dearborn counties decreased by 181 deer (6.3 percent) and 195 (7.6 percent), respectively, from 2015 totals. The deer harvest in Fayette County increased by 45 deer (4.1 percent) from 2015.
Figure 3. Number of antlered and antlerless deer harvested in Dearborn, Fayette and Franklin counties during the 2015 and 2016 Indiana deer hunting seasons.
2017 bovine tuberculosis special permits
As a result of the success of the surveillance effort, the DNR canceled previous plans to use sharpshooters to reduce the deer population in southern Fayette and Franklin counties in winter 2017. Instead, the DNR used a management plan that allowed landowners to remove a limited number of deer from their property using DNR-issued special disease control permits through March 31, 2017.
Permits were issued only to landowners within the core surveillance area established in the 3-mile circles around the bovine tuberculosis-affected sites in Franklin County. Permits allowed a limited, specified number of deer to be removed for the purposes of reducing disease risk to livestock. As part of the permit application, applicants needed to meet either one of the two conditions: 1) an economic loss of property of at least $500 caused by deer, or 2) the need to protect livestock from the potential disease risk posed by wild white-tailed deer that may be infected with bovine tuberculosis. Permit holders designated who were allowed to shoot their specified number of deer on their permit application.
The sampled hunter-harvested deer were evenly distributed throughout the enhanced surveillance area. However, some areas were not adequately sampled and additional deer needed to be tested to verify the low apparent prevalence rate of bovine tuberculosis in high-risk areas. Therefore, the heads of all deer taken using these permits were required to be submitted for bovine tuberculosis testing.
Thirty permits were issued to landowners to collect deer for disease testing. The number of deer allowed to be taken per permit ranged from one to five, for a possible total take of 114 deer. A total of 11 deer were collected by landowners using these permits.
- Bovine tuberculosis information from the Indiana Board of Animal Health
- Bovine tuberculosis and humans information from Indiana State Department of Health
Questions about bovine tuberculosis in Indiana deer
State Deer Biologist
Bovine tuberculosis hotline: (844) 803-0002