Management of bovine tuberculosis in Michigan wildlife: Current status and near term prospects

Surveillance and control activities for bovine tuberculosis (bTB) in free-ranging Michigan white-tailed deer (Odocoileus virginianus) have now been underway for over a decade. Significant progress has been made, lowering apparent prevalence in deer in the core area by >60%, primarily via reduction of deer densities through hunting, and restrictions on public feeding and baiting of deer. These broad strategies of the Michigan Department of Natural Resources (MDNR), implemented with the cooperation of Michigan deer hunters, halved the deer population in the bTB endemic area. However, as hunters see fewer deer, their willingness to sustain aggressive harvests has waned, and public resentment of control measures has grown. During the past four years, apparent prevalence in core area deer has held approximately steady just below 2%. After bottoming out in 2004 at an estimated 10–12 deer/km2, deer numbers have since rebounded by ∼30%. Public compliance with baiting and feeding restrictions has been variable. In general, hunters in the core area do not perceive bTB as a problem, in spite of 13 years of MDNR outreach. To date, MDNR has expended more than US$23milliononTB-relatedactivities.Oflate,asubstantialportionofthatfundinghasbeendivertedtosupportotherprogramswhichhavesufferedfrombudgetshortfalls.Livestockherdbreakdownscontinuetooccursporadically,averaging3–4peryear2005topresent.Intotal,46cattleand4captivedeerherdshavebeendiagnosedbTBpositivestatewide,themajorityyieldingonly1positiveanimal.Fivecattleherdsweretwiceinfected,onethrice.MichiganDepartmentofAgriculture(MDA)policyemphasishasshiftedtowardsobtainingproducersupportforwildliferiskmitigationandfarmbiosecurity.Fundinghasprovenalimitingfactor,withthemajorityoftheUS$63 million spent to date devoted to whole herd testing. Nevertheless, some initiatives justify cautious optimism. Promising research to support eventual vaccination of wild deer continues. Some hunters and landowners have begun to recognize the costs of high deer densities and supplemental feeding. A peninsula-wide ban on baiting and feeding was enacted. Some cattle producers, recognizing their precarious circumstances, have begun work to change long-held prevailing opinions among their peers about farm biosecurity. Yet formidable challenges remain, and evidence suggests that eradication of bTB, if it can be achieved, will take decades, and will require greater public and political resolve than has been demonstrated thus far.