Live-trapping and bovine tuberculosis testing of free-ranging white-tailed deer for targeted removal

Abstract

Context Significant efforts have been made in Michigan, USA, to reduce the prevalence of bovine tuberculosis (TB) in free-ranging white-tailed deer (Odocoileus virginianus) over the past 15 years. Since 2002, however, prevalence has changed little, prompting the need for new control strategies. Aims In January–March of 2007 and 2008, a trap–test–cull project was conducted on an 11 000-ha property in the north-eastern Lower Peninsula of Michigan. The objectives were to assess the feasibility of live-trapping and testing white-tailed deer for TB as a means for targeted removal and estimate the cost of this effort. Methods Live-trapped deer were ear-tagged and a blood sample was drawn for use with the CervidTB STAT-PAK (commonly called Rapid Test) for TB diagnosis in the field. Deer testing negative were released, whereas deer testing positive were euthanised to confirm blood-test results via bacterial culture. Key results In all, 762 (741 with known sex and age) individual deer were captured and tested for TB. Adults comprised 59% (437 of 741) of the captures. Eight (1.8%) adults were positive on the blood test; six of eight (1.4% of adults) were confirmed TB positive via bacterial culture. Estimated TB prevalence in the present study was 2.5% (adjusted for Rapid Test sensitivity of 56%), being lower than what would be expected on the basis of routine hunter-harvest surveillance for this site which has yielded prevalence rates from 3.4% to 4.8%. Results demonstrated the ability to trap and test a substantial number of deer given high deer densities (16–20 deer per km2), availability of traps and abundant workers. The 2-year project cost a total of ~US$228 000, or US$38 000 per culture-positive animal. Conclusions Because of the cost and effort involved, a project such as the present one applied to Michigan’s larger TB-management area (148 018 ha) is not feasible. Implications If the efficiency and effectiveness of a trap–test–cull project could be improved by vaccinating test-negative animals, should a vaccine be approved for use in free-ranging white-tailed deer, a trap–test–cull project applied on a scale similar to the present study may prove beneficial by possibly reducing disease transmission, in addition to removing TB-positive animals.