The role of wildlife in the persistence and spread of livestock diseases is difficult to quantify and control. These difficulties are exacerbated when several wildlife species are potentially involved. Bovine tuberculosis (bTB), caused by Mycobacterium bovis, has experienced an ecological shift in Michigan, with spillover from cattle leading to an endemically infected white-tailed deer (deer) population. It has potentially substantial implications for the health and well-being of both wildlife and livestock and incurs a significant economic cost to industry and government. Deer are known to act as a reservoir of infection, with evidence of M. bovis transmission to sympatric elk and cattle populations. However, the role of elk in the circulation of M. bovis is uncertain; they are few in number, but range further than deer, so may enable long distance spread. Combining Whole Genome Sequences (WGS) for M. bovis isolates from exceptionally well-observed populations of elk, deer and cattle with spatiotemporal locations, we use spatial and Bayesian phylogenetic analyses to show strong spatiotemporal admixture of M. bovis isolates. Clustering of bTB in elk and cattle suggests either intraspecies transmission within the two populations, or exposure to a common source. However, there is no support for significant pathogen transfer amongst elk and cattle, and our data are in accordance with existing evidence that interspecies transmission in Michigan is likely only maintained by deer. This study demonstrates | 2193 SALVADOR et AL.

Bovine tuberculosis (bTB) caused by Mycobacterium bovis infection in Michigan white‐tailed deer (Odocoileus virginianus) has proven resistant to current management practices. The Michigan Department of Natural Resources (MDNR) is faced with managing a protracted bTB outbreak with shrinking economic resources, its initial control strategies approaching, or having reached, the limits of their effectiveness. Planning tools are needed to project the outbreak's future course and forecast the likely outcomes of proposed controls. We describe development of a spatially explicit, individual‐based stochastic simulation model of bTB in Michigan white‐tailed deer. We sought to 1) characterize whether eradication of bTB is possible by increasing hunter harvest or via vaccination, and how long it is likely to take to achieve eradication; 2) characterize the effect of concurrent deer baiting; and 3) assess the effect of baiting on the probability of bTB establishment in uninfected areas. Simulations indicated that current MDNR management strategies are unlikely to eradicate bTB from the core outbreak area's deer population within the next 30 years. A 50–100% increase (over current rates) of both antlered and antlerless deer harvest was required to achieve eradication if baiting was occurring, compared to only a 50% increase in harvest required if baiting was eliminated. Vaccination strategies required frequent application and high exposure rates (>90%) to achieve eradication, which baiting delayed. Simulations indicated that if bTB was eradicated from the core outbreak area, a single infected deer introduced into the area would be 8 times more likely to re‐establish bTB if baiting was occurring. The ability to forecast likely outcomes of disease management can be critical for wildlife managers to assess whether specific strategies are likely to be successful. Because current policy appears unlikely to achieve the stated goal of eradicating bTB from Michigan in the foreseeable future, reorienting the bTB program from eradication to controlling geographic spread and transmission to cattle may be more realistic goals. Spatial models such as ours are ideally suited to investigating spatial heterogeneity of disease transmission, and how transmission is influenced by aggregating factors such as baiting or supplemental feeding. © 2014 The Wildlife Society.

The eradication of bovine tuberculosis (bTB), caused by Mycobacterium bovis, from cattle in many locations worldwide is complicated by endemic foci of the disease in free-ranging wildlife. Recent simulation modeling of the bTB outbreak in white-tailed deer (WTD) in Michigan, USA, suggests current management is unlikely to eradicate bTB from the core outbreak area (DMU 452) within the next three decades. However, some level of control short of eradication might sufficiently reduce transmission from deer to cattle to a point at which the negative effects of bTB on the cattle industry could be reduced or eliminated, while minimizing the negative consequences of reducing deer numbers. We extended our existing spatially-explicit, individual-based stochastic simulation model of bTB transmission in WTD to incorporate transmission to cattle, to characterize the effects of vaccination and increased harvest of WTD on cattle herd breakdown rates, to examine the effects of localized culling or vaccination of WTD in the vicinity of cattle farms, to assess the effects of concurrent deer baiting, and to determine the effect of progressive restriction of deer/cattle contact on herd breakdowns. A spatially-explicit "cattle layer" was constructed describing the spatial locations, farm size and cattle density of all farms within and directly adjacent to DMU452. Increased hunter harvest or vaccination of deer, or a combination, would likely decrease the number of cattle herd breakdowns to <1 per year in less than 15 years. Concurrent deer baiting variably increased the time necessary to achieve zero breakdowns. The prevalence of bTB in deer needed to fall below ∼0.5% before ≤1 herd breakdown per year could be expected, and below 0.1% before zero breakdowns were likely. Locally applied post-harvest deer culling or vaccination also rapidly reduced herd breakdowns. On farm biosecurity measures needed to reduce deer to cattle contact by >95% in order to reliably reduce herd breakdowns, and did not achieve zero breakdowns in the absence of other deer controls.

White-tailed deer (Odocoileus virginianus) in Michigan, USA, is one of the few species in the world considered a maintenance host for bovine tuberculosis (TB). Prevalence of TB over the past decade has remained steady in Deer Management Unit (DMU) 452 and new control strategies are needed to further reduce prevalence or eradicate the disease. There is little public support for large-scale culling of deer in Michigan, and vaccination is being considered as a potential management tool. Our goal was to evaluate the use of vaccination and/or targeted removal via live-trapping as TB control measures and how changes in vaccine parameters affect prevalence reduction. We used a spatially explicit stochastic individual-based model of TB dynamics in white-tailed deer to evaluate 39 management scenarios for their ability to 1) reach a 95% probability of eradication, and 2) lower TB prevalence over 30 years. We found continuation of current management would not result in a detectable prevalence reduction, nor would treatment of a ''hot-spot'' of infection within DMU 452. Application frequency played a larger role in prevalence reduction than vaccine efficacy, guaranteed immunity period, or half-life. Vaccination (alone or with targeted removal) applied annually throughout DMU 452 was necessary for a detectable reduction in prevalence. Projected costs for application over DMU 452 would exceed US$1.5 million annually. Vaccination will be costly and require long-term commitment, but the economic losses associated with allowing TB to persist in Michigan could outweigh vaccination costs. ß 2012 The Wildlife Society.

Surveillance and control activities related to bovine tuberculosis (TB) in free-ranging, Michigan white-tailed deer (Odocoileus virginianus) have been underway for over a decade, with significant progress. However, foci of higher TB prevalence on private lands and limited agency ability to eliminate them using broad control strategies have led to development and trial of new control strategies, such as live trapping, testing, and culling or release. Such strategies require a prompt, accurate live animal test, which has thus far been lacking. We report here the ability of seven candidate blood assays to determine the TB infection status of Michigan deer. Our aims were twofold: to characterize the accuracy of the tests using field-collected samples and to evaluate the feasibility of the tests for use in a test-and-cull strategy. Samples were collected from 760 deer obtained via five different surveys conducted between 2004 and 2007. Blood samples were subjected to one or more of the candidate blood assays and evaluated against the results of mycobacterial culture of the cranial lymph nodes. Sensitivities of the tests ranged from 46% to 68%, whereas specificities and negative predictive values were all >92%. Positive predictive values were highly variable. An exploratory analysis of associations among several host and sampling-related factors and the agreement between blood assay and culture results suggested these assays were minimally affected. This study demonstrated the capabilities and limitations of several available blood tests for Mycobacterium bovis on specimens obtained through a variety of field surveillance methods. Although these blood assays cannot replace mass culling, information on their performance may prove useful as wildlife disease managers develop innovative methods of detecting infected animals where mass culling is publicly unacceptable and cannot be used as a control strategy.