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Since 1994, the state of Michigan has recognized a problem with bovine tuberculosis (TB), caused by Mycobacterium bovis, in wild white-tailed deer from a 12-county area in northeastern Lower Michigan. A total of 65,000 free-ranging deer have been tested, and 340 have been found to be positive for M. bovis. The disease has been found in other wildlife species, and, in 1998, in domestic cattle, where to date 13 beef cattle and 2 dairy cattle herds have been diagnosed with bovine TB. Unfortunately, the situation is unique in that there have never been reports of self-sustaining bovine TB in a wild, free-ranging cervid population in North America. Scientists, biologists, epidemiologists, and veterinarians who have studied this situation have concluded that the most logical theory is that high deer densities and the focal concentration caused by baiting (the practice of hunting deer over feed) and feeding are the factors most likely responsible for the establishment of self-sustaining TB in free-ranging Michigan deer. Baiting and feeding have been banned since 1998 in counties where the disease has been found. In addition, the deer herd has been reduced by 50% in the endemic area with the use of unlimited antlerless permits. The measures of apparent TB prevalence have been decreased by half since 1997, providing hopeful preliminary evidence that eradication strategies are succeeding.

No abstract

During a survey of carnivores and omnivores for bovine tuberculosis conducted in Michigan (USA) since 1996, Mycobacterium bovis was cultured from lymph nodes pooled from six coyotes (Canis latrans) (four adult female, two adult male), two adult male raccoons (Procyon lotor), one adult male red fox (Vulpes vulpes), and one 1.5-yr-old male black bear (Ursus americanus). One adult, male bobcat (Felis rufus) with histologic lesions suggestive of tuberculosis was negative on culture but positive for organisms belonging to the Mycobacterium tuberculosis complex when tested by polymerase chain reaction. All the tuberculous animals were taken from three adjoining counties where M. bovis is known to be endemic in the free-ranging white-tailed deer (Odocoileus virginianus) population. There were two coyotes, one raccoon, one red fox, and one bobcat infected in Alpena county. Montmorency County had two coyotes and one raccoon with M. bovis. Two coyotes and a bear were infected from Alcona County. These free-ranging carnivores/omnivores probably became infected with M. bovis through consumption of tuberculous deer. Other species included in the survey were opossum (Didelphis virginiana), gray fox (Urocyon cinereoargenteus), and badger (Taxidea taxus); these were negative for M. bovis.

Bovine tuberculosis (bTb) was diagnosed in 22 cattle herds in the northeast comer of Michigan's lower peninsula. Of these 22 herds, 494 animals in 7 herds were examined by gross necropsy, histopathologic exam, mycobacterial culture, and polymerase chain reaction (PCR) assay performed only on samples that were histologically compatible for bTb. Results of culture and PCR assay interpreted in parallel were used as the reference test for calculation of the sensitivity of 1) the caudal fold test (CFT), 2) the caudal fold and comparative cervical skin tests used in series (CFTCCTSER), and 3) gross necropsy. Mycobacterium bovis was isolated from 43 animals. Using all 7 herds, the sensitivities of the CFT, the CFTCCTSER, and gross necropsy were 93.02%, 88.37%, and 86.05%, respectively. When the data were stratified by low- and moderate-prevalence herds, the sensitivities were 83.33%, 75.0%, and 83.33% in low-prevalence herds and 96.77%, 93.55%, and 87.10% in moderate-prevalence herds. The sensitivities of the 2 skin tests were slightly higher when 2 or more gross lesions were present, and the sensitivity of gross necropsy was significantly higher (P = 0.049). The sensitivity of the CFT was found to be notably higher than most estimates in other studies; however, a direct comparison was not possible because the amount of purified protein derivative and the reference methods were different in this study compared with other published studies. Although the sensitivities are high, 2 of the 7 herds (29%) would have had 1 or more positive animals left in the herd if a test-and-removal program had been used. This suggests that when positive herds are identified, selective culling of skin test reactors is a less acceptable disease control strategy than is complete depopulation.

Objective—To determine the distribution of lesions and extent of tissues infected with Mycobacterium bovis in a captive population of white-tailed deer. Design—Cross-sectional study. Animals—116 captive white-tailed deer. Procedure—Deer were euthanatized, and postmortem examinations were performed. Tissues with gross lesions suggestive of tuberculosis were collected for microscopic analysis and bacteriologic culture. Tissues from the head, thorax, and abdomen of deer with no gross lesions were pooled for bacteriologic culture. Tonsillar, nasal, oral, and rectal swab specimens, fecal samples, and samples of hay and pelleted feed, soil around feeding sites, and water from 2 natural ponds were collected for bacteriologic culture. Results—Mycobacterium bovis was isolated from 14 of 116 (12%) deer; however, only 9 of 14 had lesions consistent with tuberculosis. Most commonly affected tissues included the medial retropharyngeal lymph node and lung. Five of 14 tuberculous deer had no gross lesions; however, M bovis was isolated from pooled tissue specimens from the heads of each of these deer. Bacteriologic culture of tonsillar swab specimens from 2 of the infected deer yielded M bovis. Mean (± SEM) age of tuberculous deer was 2.5 ± 0.3 years (range, 0.5 to 6 years). Mycobacterium bovis was not isolated from feed, soil, water, or fecal samples. Conclusions and Clinical Relevance—Examination of hunter-killed white-tailed deer for tuberculosis commonly includes only the lymph nodes of the head. Results of such examinations may underestimate disease prevalence by as much as 57%. Such discrepancy should be considered when estimating disease prevalence. (J Am Vet Med Assoc 2000;216:1921–1924)

Despite ongoing eradication efforts, bovine tuberculosis (BTB) remains a challenge in Michigan livestock and wildlife. The objectives of this study were to (1) review the epidemiology of BTB in Michigan cattle, privately owned cervids, and wildlife between 1975 and 2010 and (2) identify important lessons learned from the review and eradication strategies. BTB information was accessed from the Michigan BTB Eradication Project agencies. Cattle herds (49), privately owned deer herds (4), and wild white-tailed deer (668) were found infected with BTB during the review period. BTB has occurred primarily in counties located at the northern portion of the state's Lower Peninsula. Currently used BTB eradication strategies have successfully controlled BTB spread. However additional changes in BTB surveillance, prevention, and eradication strategies could improve eradication efforts.

A retrospective study of various diagnostic postmortem techniques used in a 4-year surveillance program for detection of Mycobacterium bovis infection in wild white-tailed deer (Odocoileus virginianus) was conducted. The tests evaluated were routine histopathology, acid-fast staining, detection of acid-fast bacilli in culture, and an M. tuberculosis group-specific genetic probe applied to pure cultures. Each of these techniques were compared with a reference or "gold standard" of mycobacterial culture and identification. Histopathology, the most rapid form of testing for M. bovis infection in white-tailed deer samples, had a sensitivity of 98% and a specificity of 87%, resulting in a positive predictive value of 94%. The detection of acid-fast bacilli by staining was less sensitive than histopathology (90%), but its higher specificity (97%) resulted in a positive predictive value of 99%. The detection of acid-fast bacilli on culture was both highly specific (93%) and sensitive (100%). The group-specific genetic probe had the highest sensitivity and specificity and produced results in complete agreement with those of mycobacterial culture, suggesting that this technique could be used as the new "gold standard" for this particular wildlife tuberculosis surveillance program.