Managing Bovine Tuberculosis in White-Tailed Deer in Northwestern Minnesota: A 2008 Progress Report

Bovine tuberculosis (TB), first discovered in 2005, has now been found in 12 cattle operations in northwestern Minnesota. To date, all of the infected cattle herds have been depopulated and the Board of Animal Health (BAH) has continued to test cattle herds in the area. The strain has been identified as one that is consistent with Bovine TB found in cattle in the southwestern United States and Mexico. In response to the disease being detected in cattle, the Minnesota Department of Natural Resources (MNDNR) began surveillance efforts in free-ranging white-tailed deer (Odocoileus virginianus) within a 15-mile radius of the infected farms in fall 2005. To date, 25 deer have been found infected with Bovine TB. All infected deer were sampled within a 164mi2 area, called the Bovine TB Core, which is centered in Skime, Minnesota, and encompasses 8 of the previously infected cattle farms. In fall 2008, Minnesota was granted a Split-State Status for Bovine TB by the United States Department of Agriculture (USDA) that resulted in a lessening of testing requirements for cattle in the majority of the state (status level = “Modified Accredited advanced”), with a small area in northwestern Minnesota remaining more restrictive (status level = “Modified Accredited”). Also in 2008, the Minnesota State Legislature passed an initiative that allocated funds to buy-out cattle herds located in the Bovine TB Management Zone, spending $3 million to remove 6,200 cattle from 46 farms by January 2009; resulting in the discovery of the 12th infected cattle herd. The remaining cattle farms in the Bovine TB Management Zone (n = 27) were required to erect deer-exclusion fencing to protect stored forage and winter feeding areas, costing an additional$690,000 in state funds. In November 2008, the MNDNR conducted Bovine TB surveillance of hunter-harvested white-tailed deer within the newly created Modified Accredited Zone, and results indicated that none of the 1,246 deer tested were positive for the disease. This marked the first large scale surveillance effort that failed to detect the disease in hunter-harvested deer since sampling efforts began in 2005. MNDNR also conducted targeted removal operations in the Bovine TB Core Area, using both aerial and ground sharpshooting, during winters 2007, 2008 and 2009. These intensive winter deer removal operations removed a combined total of 2,163 deer and detected 13 (52%) of the TB-positive deer discovered to date. Further, a recreational feeding ban, covering 4,000mi2 in northwestern MN, was instituted in November 2006 to help reduce the risk of deer to deer transmission of the disease and enforcement officers have been working to stop illegal feeding activities. The MNDNR will continue to conduct hunter-harvested surveillance for the next 5 years to monitor infection in the local deer population, and consider the continuation of aggressive management actions (e.g., sharpshooting deer in key locations) to address concerns of deer becoming a potential disease reservoir

Managing Bovine Tuberculosis in White-Tailed Deer in Northwestern Minnesota: A 2007 Progress Report

Bovine tuberculosis (TB), first discovered in 2005, has now been found in 11 cattle operations in northwestern Minnesota. To date, all of the infected cattle herds have been depopulated and the Board of Animal Health (BAH) has continued an investigation of herds in the area as well as conducted a statewide surveillance effort. The strain has been identified as one that is consistent with bovine TB found in cattle in the southwestern United States and Mexico. In November 2007, the Minnesota Department of Natural Resources (MNDNR) conducted bovine TB surveillance of hunter-harvested white-tailed deer (Odocoileus virginianus) within a 15-mile radius of the infected farms. Results indicated that 5 of the 1,085 deer tested positive for bovine TB; estimated disease prevalence of 0.46% (SE=0.2%). All infected deer were harvested within 5 miles of Skime, Minnesota, which is in close proximity to 7 of the infected livestock operations. In response to additional deer found infected with bovine TB since 2005, the MNDNR also conducted a targeted deer removal operation during winter 2007, using sharpshooters from the United States Department of Agriculture (USDA) Wildlife Services. An additional 488 deer were removed through this project, yielding 6 more cases of infected deer. Further, a recreational feeding ban, covering 4,000 mi2 in northwestern MN, was instituted in November 2006 to help reduce the risk of deer to deer transmission of the disease and enforcement officers have been working to stop illegal feeding activities. Also, in 2006, the Minnesota State Legislature passed an initiative that allocated $54,000 to deer-proof fencing materials for livestock producers within 5 miles of a previously infected farm; MNDNR erected 15 fences on 11 cattle premises during summer 2007. The findings of additional infection in cattle herds as well as the deer has resulted in the downgrading of Minnesota’s bovine TB status to “modified accredited”, which has increasing testing requirement for cattle statewide. The MNDNR will continue to conduct hunter-harvested surveillance in fall 2008 to monitor infection in the local deer population, and consider the continuation of aggressive management actions (e.g., sharpshooting deer in key locations) to address concerns of deer becoming a potential disease reservoir