Additionally, MNDNR attempted to further reduce deer numbers in the posthunting season in the Bovine TB Core Area through the use of sharpshooters.  The goal was to harvest as many deer as possible in hopes of removing additional bTB-infected deer from this critical area, thus, reducing the potential for deer-deer or deer-cattle transmission.  Disease prevalence data generated from this removal effort were biased by targeting deer from known bTB-infected areas.  During winters 2007-2010, sharpshooting from the ground was conducted by USDA-Wildlife Services (USDA-WS) professionals; supplemental sharpshooting was conducted by aerial operations during winters 2007 (Wildlife Services, Inc.) and 2008 (Tery Jon Aviation).  Sharpshooter-harvested deer were transported intact to a central processing facility at Thief Lake Wildlife Management Area in northwest Minnesota.  All deer were sampled, including fawns (<1.0 year old).  Sample collection and handling is described below.  Carcasses that were free of any visible lesions were salvaged for venison and made available to the public.
 Six cranial lymph nodes (parotid, submandibular, and medial retropharyngeal) extracted from all deer by trained personnel were submitted for testing, regardless of surveillance method.  Once extracted, all lymph nodes were cross-sectioned for presence of gross lesions.  Tissue collection procedures included a visual inspection of the chest cavity of the hunter-killed deer (lungs were typically not available as carcasses were field-dressed).  Any suspect carcasses (e.g., obvious lesions in chest cavity or lymph nodes) were confiscated at the registration stations, and the hunter was issued a replacement deer license at no charge.  A first incisor was collected for aging by cementum annuli.  Suspect carcasses were transported in their entirety to the Veterinary Diagnostic Laboratory (VDL) at the University of Minnesota for further testing. Samples collected from sharpshooter-killed deer, vehicle-killed deer within the bTB Management Zone, or deer harvested by landowner shooting permit were handled as described above.
All lymph node samples were first submitted to the VDL for histological examination and acid-fast staining, and then forwarded to the National Veterinary Services Laboratories (NVSL) in Ames, IA for bacterial culture.  Real-time polymerase chain reaction (RT PCR) was used to detect the presence of M. tuberculosis complex DNA when obvious lesions were present, which was then followed by bacterial culture.  Samples that did not have obvious lesions were pooled in groups of 5 deer and also cultured. Bacterial growth identified as M. bovis indicates the animal was infected with bTB.  These cultures were submitted for further laboratory testing to compare similarities or differences with other cultures of M. bovis identified within Minnesota and strains identified in the reference collection at NVSL.
 Deer surveys were conducted in late January:early February 2007-2010 to estimate deer densities and monitor changes in the abundance and distribution of deer within the bTB Core Area relative to ongoing management actions.  The target population was free-ranging white-tailed deer within the 425-km2 bTB Core Area.  We used an equal-probability, generalized random-tessellation, stratified sampling design, which generated a 2D spatially balanced sample.  The sampling frame included 164 Public Land Survey sections with a sample size of 72 plots (sampling rate = 0.439). Surveys were conducted by helicopter (Bell OH-58, Jet Ranger [2007-2008, 2010]; Enstrom 480B [2009]) with a pilot and 2 observers.  Population estimates reflected the minimum numbers of deer present during the sampling interval, as estimates were not adjusted for detectability.  Deer movements between sample plots were assumed to be minimal.  Confidence intervals (95% CIs) were based on sampling variance only and did not include uncertainty associated with detectability or animal movements.