Value of existing serological tests for identifying badgers that shed Mycobacterium bovis

In the UK there has been a sharp rise in the incidence of bovine tuberculosis since the early 1990s and the badger has been identified as an important wildlife reservoir for this infection. Infected badgers can excrete Mycobacterium bovis, putting other badgers and cattle at risk of becoming infected. Vaccination has been proposed as an approach to reducing the excretion of M. bovis by tuberculous badgers. In order to evaluate the efficacy of a badger vaccine it will be necessary to accurately determine the number of badgers excreting M. bovis without removing them for post-mortem evaluation. The existing live tests for tuberculosis in the badger (culture, indirect ELISA, Western blot) have not been assessed for their ability to detect badgers excreting M. bovis. Over the past 18 years, badgers from 31 social groups have been trapped and sampled in a study area of the Cotswold escarpment. We have examined the serological responses of 128 badgers trapped between 1985 and 1998 from social groups where M. bovis infection was endemic. These responses were compared with culture from faeces, urine, tracheal aspirates and bite wound swabs taken from these animals while alive. ELISA was found to be more sensitive than Western blot in detecting badgers excreting M. bovis. The majority of culture-positive badgers excreted M. bovis intermittently over the period of study. As a result, there was only a 27.5% chance of sampling a badger for culture when it was excreting M. bovis. In contrast, a positive ELISA result correctly predicted 68.2% of badgers with a history of excreting M. bovis. In the absence of alternative live tests for the badger, the Brock Test indirect ELISA appears to be more valuable than culture for measuring the effect of vaccination on reducing the number of badgers at risk of transmitting tuberculosis.     

Antigen specific immunological responses of badgers (Meles meles) experimentally infected with Mycobacterium bovis

European badgers (Meles meles) are considered to be an important reservoir of infection for Mycobacterium bovis and are implicated in the transmission of tuberculosis to cattle in Ireland and Great Britain. Accurate tests are required for tuberculosis surveillance in badger populations and to provide a basis for the development of strategies, including vaccination, to reduce the incidence of the infection. In this study, we have developed an endobronchial M. bovis infection model in badgers in which we measured cell-mediated immune and serological responses for up to 24 weeks post-infection. Groups of badgers were subjected to necropsy at 6-week intervals and the gross lesion severity status compared with immune responses measured in blood samples taken throughout the course of the study. The panel of antigens included bovine and avian tuberculins (PPD) as well as single antigens, ESAT-6, CFP-10, MPB70, Rv3019c, Rv3873, Rv3878 and Rv3879, all known to be recognised by the immune system in other animal models of tuberculosis infection. Our results demonstrated that M. bovis infected badgers responded to specific antigens as early as 6 weeks post-infection, consistent with the presence of visible lesions. The data also revealed unique patterns of antigen recognition with high levels of PBMC proliferation in the presence of CFP-10 but low proliferation levels with ESAT-6. Using a multi-antigen print immunoassay (MAPIA), we were able to confirm that MPB83 is the dominant antigen recognised by serum antibodies in infected badgers.     

Immunological responses of Eurasian badgers (Meles meles) vaccinated with Mycobacterium bovis BCG (bacillus calmette guerin)

Wildlife species, such as the badger (Meles meles), may act as maintenance hosts for Mycobacterium bovis and contribute to the spread and persistence of tuberculosis in associated cattle populations. Targeted vaccination of badgers against tuberculosis is an option that, if successfully employed, could directly facilitate the advancement of bovine tuberculosis eradication in affected areas. In this study, the immunological responses of a group of badgers vaccinated subcutaneously with low doses of Mycobacterium bovis bacillus calmette guerin (BCG) were measured in vitro and compared with non-vaccinated control animals over a period of 42 weeks. Peripheral blood mononuclear cells (PBMC) from badgers which had received repeated booster injections of BCG proliferated in response to culture with PPD-bovine (purified protein derivative of tuberculin). The proliferation was significantly greater than that seen in the non-vaccinated control group. In contrast, the proliferative response of PBMC from vaccinated badgers to PPD-avian declined relative to the control group. These results demonstrate that repeated vaccination of badgers with M. bovis BCG induced a population of T-lymphocytes responsive to specific antigens in PPD-bovine. Throughout the course of the study, the sera from all animals were tested (BrockTest) by an enzyme-linked immunosorbent assay (ELISA) system for the presence of antibodies to MPB83, a serodominant antigen whose expression is high in M. bovis, but very low in BCG (Pasteur). No animals at any stage showed seroconversion to the antigen, consistent with the tuberculosis-free status of the badgers under study.     

Experimental tuberculosis in the European badger (Meles meles) after endobronchial inoculation of Mycobacterium bovis: I. Pathology and bacteriology

The aim was to develop an endobronchial infection procedure for the study of Mycobacterium bovis infection in badgers. The badgers were anaesthetised and a cannula was passed per os to the tracheal bifurcation. When in place 1 ml of M. bovis suspension was inoculated. Three concentrations of M. bovis suspension were used; <10 colony forming units (cfu), approximately 10(2) cfu and approximately 3 x 10(3) cfu. The badgers were examined at three weekly intervals for clinical signs of disease and a tracheal aspirate was collected at each examination. The badgers were euthanased 17 weeks post infection (pi) and at the post mortem examination a wide range of tissues were examined for gross and histopathological lesions of tuberculosis and cultured for M. bovis. A sample of bronchial alveolar lavage (BAL) fluid was collected at post mortem for culture. At post mortem examination 17 weeks after infection, gross and histopathological lesions of tuberculosis were observed in all badgers inoculated with the high and medium dose and 1/3 inoculated with the low dose. M. bovis was recovered from all inoculated badgers. Infection in the high dose group was more widely disseminated than in the other groups. The number of sites with gross and histopathological lesions increased with increasing dose of M. bovis. All tracheal aspirates were negative on culture and only one BAL, collected from a badger of the high dose group, was positive on culture. No clinical signs due to the experimental infection were observed. The endobronchial route of inoculation is an effective route for establishing experimental infection, and could be used for studies of tuberculosis pathogenesis, immunology of M. bovis infection in badgers and for challenging badgers in vaccine protection studies. Badgers appeared to be very susceptible to infection by this procedure even with a dose of < 10 cfu but appear to control and limit the resulting infection.     

Laboratory study of Mycobacterium bovis infection in badgers and calves

Two experiments with badgers infected with Mycobacterium bovis are described. In the first, badgers were infected by intravenous inoculation of a bovine isolate of M bovis. The course of the disease in these and its spread to healthy badgers and calves was monitored by clinical, immunological and bacteriological means. In the second experiment a group of naturally infected badgers were observed for a period of up to four years. They were found to excrete M bovis in their faeces for periods of between 165 and 1305 days before they died of tuberculosis or were killed. M bovis was also shed in the urine. The badgers in both experiments were examined regularly and blood samples were taken for complement fixation tests. Faeces, urine, pus and sputum were also collected for cultural and biological tests and the badgers were skin tested using Weybridge bovine and avian tuberculin. The skin tests were uniformly negative while the complement fixation test were positive in some infected badgers but gave very variable results. Only the isolation of M bovis gave a definite diagnosis of tuberculosis in the living badger but a number of badgers which were found to have tuberculosis at post mortem were not detected while alive by this method. Environmental samples from the yards, including badger faeces, soil, hay, scrapings from feeding bowls and water were regularly examined for the presence of M bovis but apart from faeces only one water sample was positive, indicating that the organism did not persist for long in the environment. In both experiments calves developed sensitivity to bovine tuberculin after six months' exposure to infected badgers. The experiments further demonstrate the potential of a badger population to become endemically infected with M bovis and to act as a source of infection for cattle.     

Detection of Mycobacterium bovis infection and production of interleukin-2 by in vitro stimulation of badger lymphocytes

The Eurasian badger (Meles meles) is considered to be an important wildlife reservoir for Mycobacterium bovis infection of cattle in Ireland and in GB. However, rapid diagnosis of tuberculosis in live badgers has been constrained through a lack of suitable immuno-diagnostic reagents for detection of M. bovis-infected animals. To date, there have been no reports of cytokine activity in badgers that might be associated with specific immune responses to M. bovis infection. In this study, nine badgers were removed from an area with a persistent tuberculosis problem in cattle herds and tuberculosis was confirmed in four of the animals by "post-mortem" examination and M. bovis culture. In preliminary investigations of interleukin-2 (IL-2) activity, we were able to demonstrate that lymphoblasts prepared from badger peripheral blood mononuclear cells (PBMCs) proliferated when cultured in the presence of human recombinant IL-2 (HrIL-2). Supernatants derived from purified protein derivative of tuberculin (PPD-bovine) stimulated PBMC cultures also induced blastogenesis of badger-derived lymphoblasts. The results demonstrate that badger lymphocytes are responsive to HrIL-2 and that PPD-bovine stimulation of badger PBMC results in production of bio-active IL-2.     

Trial design to estimate the effect of vaccination on tuberculosis incidence in badgers

The principal wildlife reservoir of Mycobacterium bovis in Ireland is the European badger. Studies in the Republic of Ireland (RoI) have shown that badgers culled in association with cattle herd tuberculosis breakdowns (focal culling) have a higher prevalence of infection than the badger population at large. This observation is one rationale for the medium term national strategy of focal badger culling. A vaccination strategy for the control of bovine tuberculosis (bTB) in badgers is a preferred long-term option. The Bacillus Calmette-Guérin (BCG) vaccine has been shown to decrease disease severity in captive badgers under controlled conditions. As the vaccine has been tested in a controlled environment with precise information on infection pressure, it cannot be assumed a priori that the effects of vaccination are similar in the wild, where other environmental and/or ecological factors prevail. For this reason we have designed a vaccine field trial to assess the impact of vaccination on the incidence of TB infection in a wild badger population. The selected study area for the vaccine trial (approximately 755 square kilometers) is divided into three zones each of which has similar characteristics in terms of size, number of main badger setts, cattle herds, cattle and land classification type. Three vaccination levels (100%, 50% and 0%) will be allocated to the three zones in a way that a gradient of vaccination coverage North to South is achieved. The middle zone (zone B) will be vaccinated at a 50% coverage but zone A and C will be randomly allocated with 100% or 0% vaccination coverage. Vaccination within zone B will be done randomly at individual badger level. The objective of this paper is to describe the design of a field tuberculosis vaccination trial for badgers, the epidemiological methods that were used to design the trial and the subsequent data analysis. The analysis will enable us to quantify the magnitude of the observed vaccination effect on M. bovis transmission in badgers under field conditions and to improve our knowledge of the biological effects of vaccination on susceptibility and infectiousness.     

Vaccinating badgers (Meles meles) against Mycobacterium bovis: the ecological considerations

Bovine tuberculosis (TB) is a serious zoonotic disease, which despite a largely successful test and slaughter programme has persisted in cattle herds in parts of the UK. The badger (Meles meles) is widely considered to represent a significant wildlife reservoir for the transmission of Mycobacterium bovis to cattle, and has been the subject of a variety of culling strategies since the mid 1970s. Nevertheless, the incidence of herd breakdowns has continued to rise, and the efficacy of culling is currently the subject of a large-scale field trial. One potential alternative tool for the management of disease in wildlife populations is vaccination. However, the successful development of an effective vaccine and a strategy for its delivery will require careful consideration of the practical constraints imposed by ecological factors. In the current paper, we discuss relevant ecological and epidemiological characteristics of badger populations and practical aspects of vaccine delivery in the field.     

Differential antigen recognition by serum antibodies from three bovid hosts of Mycobacterium bovis infection

Cattle, bison and buffaloes are susceptible to Mycobacterium bovis, the causative agent for bovine tuberculosis. Accurate and timely identification of infected animals is critical for improved management and control of disease in these species. Bovids develop humoral immune responses to M. bovis infection making serological tests attractive for tuberculosis screening. However, optimization and validation of antibody assays designed for various animal species require understanding of antigen recognition patterns in each target host. The objective of this study was to characterize serological reactivity profiles generated by cattle, American bison, and African buffaloes in tuberculosis. Serum samples from M. bovis-infected animals were tested for the presence of IgM and IgG antibodies to MPB70/MPB83 and CFP10/ESAT6 chimeric proteins using Dual-Path Platform technology. All three host species showed IgG responses of higher magnitude and frequency than IgM responses; further, IgM seroreactivity was limited to MPB70/MPB83, whereas IgG antibodies recognized both test antigens. In cattle, the IgM and IgG responses were elicited mainly by MPB70/MPB83, whereas bison and buffaloes showed similar IgG seroreactivity rates for MPB70/MPB83 and CFP10/ESAT6 antigens. The findings demonstrate distinct patterns of predominant antigen recognition by different bovid species in M. bovis infection.     

Use of DNA amplification for the rapid identification of Mycobacterium bovis

DNA amplification using the polymerase chain reaction technique was evaluated for rapid identification of Mycobacterium bovis. Two oligonucleotide primers of 20 bases in length were constructed to target a region of the gene encoding the M. bovis secretory protein, MPB70. The amplification reaction produced a single product 372 bp in size which was readily detected by agarose gel electrophoresis. All 84 strains of M. bovis tested produced a positive signal in the amplification reaction. In addition all isolates fro the M. tuberculosis complex tested, with the exception of M. microti, gave a single band at 372 bp. No amplified product was detected when 24 other species of mycobacteria and species from four other genera were tested. The sensitivity of the test was such that a single viable cell could be detected in the reaction. This technique provides a simple and extremely sensitive method of identifying isolates of M. bovis and other pathogenic M. tuberculosis complex organisms.     

牛结核病抗体胶体金快速检测技术的建立和应用

为了建立一种快速检测牛分支杆菌抗体的新方法用于诊断牛结核病,利用胶体金免疫层析技术原理,用原核诱导表达的牛分支杆菌抗原蛋白MPB83和MPB70分别作为胶体金标记抗原和检测线上的捕获抗原,制备牛结核抗体检测试纸条.结果表明,粒径为40 nm的胶体金制备的试纸条敏感性最高,胶体金最佳标记pH为6.0,MPB83抗原最适标记量为每毫升胶体金6.5 μg,MPB70抗原的最适包被浓度为3.0 mg/mL,抗MPB83蛋白IgG的最佳包被浓度为2.5 mg/mL,交叉试验证明试纸条不与牛的其他非相关疾病的阳性血清反应,具有较高的特异性.比较试验证明其敏感性显著高于韩国进口试纸条.在上述试验条件下生产了一批胶体金试纸条进行临床样品检测,并与细菌分离培养、结核菌素皮内变态反应(TST)和韩国试纸条比较.本试纸条与牛分支杆菌分离培养的符合率为85%,与TST的符合率为79.73%,与韩国试纸条的符合率为98.75%.快速检测牛结核抗体的免疫层析试纸条具有敏感、特异、简便、快速的特点,适用于对牛结核病进行普查和检疫,也可作为TST的辅助诊断方法,在牛结核病根除计划中具有良好的应用前景.     

Evaluation of three serological assays for the diagnosis of Mycobacterium bovis infection in brushtail possums

Three serological tests for the diagnosis of Mycobacterium bovis infection were evaluated on 29 possums (Trichosurus vulpecula) with tuberculosis and on 100 possums from a tuberculosis-free area. An indirect ELISA using M. bovis culture filtrate as the antigen had a sensitivity of 45% and a specificity of 96%, while an indirect ELISA using a M. bovis specific antigen (MPB70) had a sensitivity of 21% and a specificity of 98%. A blocking ELISA which utilised a monoclonal antibody against MPB70 had a sensitivity of 28% and a specificity of 99%. Combination of the test results of the three ELISAs resulted in an increase in sensitivity to 51% and a decrease in specificity to 93%. A previous study has shown that possums experimentally infected with M. bovis produced cellular responses to M. bovis antigens relatively early in the infection, but these responses decreased in the terminal stages of the disease. In contrast, analysis of serological responses in the current study from sequentially collected sera of possums experimentally and naturally infected with M. bovis showed that antibody was first detected late in the disease.     

Animal-side serologic assay for rapid detection of Mycobacterium bovis infection in multiple species of free-ranging wildlife

Numerous species of mammals are susceptible to Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). Several wildlife hosts have emerged as reservoirs of M. bovis infection for domestic livestock in different countries. In the present study, blood samples were collected from Eurasian badgers (n=1532), white-tailed deer (n=463), brushtail possums (n=129), and wild boar (n=177) for evaluation of antibody responses to M. bovis infection by a lateral-flow rapid test (RT) and multiantigen print immunoassay (MAPIA). Magnitude of the antibody responses and antigen recognition patterns varied among the animals as determined by MAPIA; however, MPB83 was the most commonly recognized antigen for each host studied. Other seroreactive antigens included ESAT-6, CFP10, and MPB70. The agreement of the RT with culture results varied from 74% for possums to 81% for badgers to 90% for wild boar to 97% for white-tailed deer. Small numbers of wild boar and deer exposed to M. avium infection or paratuberculosis, respectively, did not cross-react in the RT, supporting the high specificity of the assay. In deer, whole blood samples reacted similarly to corresponding serum specimens (97% concordance), demonstrating the potential for field application. As previously demonstrated for badgers and deer, antibody responses to M. bovis infection in wild boar were positively associated with advanced disease. Together, these findings suggest that a rapid TB assay such as the RT may provide a useful screening tool for certain wildlife species that may be implicated in the maintenance and transmission of M. bovis infection to domestic livestock.     

The status of Mycobacterium bovis infection in UK wild mammals: a review

Bovine tuberculosis caused by Mycobacterium bovis is a zoonotic infection with a wide range of mammalian hosts. In parts of the UK M. bovis infection in cattle is a persistent problem. The European badger (Meles meles) is implicated in the transmission of M. bovis to cattle, and is widely believed to constitute the most important reservoir of infection in UK wildlife. However, few studies have been carried out on the status of M. bovis infection in other UK mammals. In this review we present information on the incidence and pathology of M. bovis infection in UK wild mammals from both published and previously unpublished sources. Although the evidence does not support the existence of a significant self-maintaining reservoir of infection in any wild mammal other than the badger, there is a clear lack of sufficient data to rule out the involvement of other species. In the light of this and the dynamic nature of epidemiological patterns, further surveillance for M. bovis infection in UK wild mammals, using modern methods of diagnosis, is essential.     

Tuberculosis in cattle herds are sentinels for Mycobacterium bovis infection in European badgers (Meles meles): the Irish Greenfield Study

In Ireland badgers are removed in response to tuberculosis (TB) breakdowns in cattle herds (focal culling). Prevalence studies, conducted using a detailed post mortem and bacteriological examination, showed that 36-50% of badgers were infected with Mycobacterium bovis. Focal culling forms part of the medium term national strategy for the control of bovine TB in cattle and is based on the premise that badgers in areas with herd breakdowns have a higher prevalence of infection than the badger population at large. However, the hypothesis that cattle can be used as sentinels for infection in the badger population has never been formally tested. In this study we tested the hypothesis by determining the infection prevalence in badgers in areas where there had been historically, a consistently low prevalence of infection in cattle. Low cattle TB prevalence areas were defined as those herds with ≤ 2 standard reactors in the annual round of skin testing over the preceding 5 years (Greenfield sites). Using GIS, and adjusting for variation in land use, previous culling and cattle density, 198 Greenfield sites were identified and surveyed, and 138 areas with badger setts or signs of badger activity were identified. A single badger was removed from 87 sites and all were examined using detailed post mortem and bacteriological procedures. A prevalence of M. bovis infection of 14.9% was found in the Greenfield site badgers. This prevalence was significantly lower (P<0.001) than in badgers removed during focal culling (36.6%). The results validate the use of cattle as sentinels for TB in badgers and support the medium term national strategy for the control of bovine TB. The geographic variation in M. bovis infection prevalence in the Irish badger populations will be used when devising strategies for the incorporation of badger vaccination into the long term bovine TB control programme.     

BCG vaccination against tuberculosis in European badgers (Meles meles): a review

Tuberculosis (TB) is a significant animal health problem in many parts of the world, and reservoirs of infection in wild animals complicate disease control efforts in farmed livestock, particularly cattle. Badgers (Meles meles) are a significant wildlife reservoir of Mycobacterium bovis infection for cattle in the United Kingdom (UK) and Republic of Ireland (ROI). Vaccination of badgers using an M. bovis strain bacille Calmette-Guérin (BCG) vaccine could potentially be an option in the national TB eradication strategy. Wildlife vaccination has been used successfully for other diseases in wildlife species, and may have a role to play in reducing M. bovis transmission at the wildlife-livestock interface. Research to date has provided evidence that BCG is protective in badgers, and a parenteral badger BCG vaccine has been licensed in the UK. Further research is required to develop effective strategies for vaccine deployment and to determine the effect of badger vaccination on cattle TB incidence.     

Antigenic characterization of mycobacteria from South American wild seals.

Tuberculosis-producing mycobacteria have been previously described in marine mammals (Cousins et al., 1990, 1993; Romano et al., 1995; Bernardelli et al., 1996). The strains belonged to the M. tuberculosis complex (M. tuberculosis, M. bovis, M. microti and M. africanum), but showed genetic and biochemical differences. The antigenic composition of mycobacteria isolated from wild seals was analyzed by Western blots, using antibodies against some selected antigens. The antigenic content was compared with that of M. bovis, M. tuberculosis and M. microti isolates. The lack of Hsp65 protein in supernatants suggested a low degree of cell lysis in the three-week cultures used. SOD, P27 lipoprotein, MPB64 and antigen 85 were observed in all the strains studied. The wild seal strains, as well as M. tuberculosis, did not produce MPB70 and MPB83. Only very weak bands of P36 antigen were observed in culture supernatants from wild seal mycobacteria. Summarizing, the antigenic composition of mycobacterial strains from wild seals is different from M. bovis strains.     

间接ELISA检测牛分枝杆菌抗体方法的建立及初步应用

针对现行牛结核病检疫方法结核菌素皮内变态反应(TST)的不足,本研究选用牛分枝杆菌特异性抗原MPB83、MPB70及CFP10与ESAT-6融合蛋白(CFP10-ESAT-6)分别建立了检测牛分枝杆菌特异抗体的间接酶联免疫吸附方法(ELISA)。上述3种抗原中一种以上抗原的特异性抗体为阳性时,即可判断为结核检测阳性。以TST为标准,判断ELISA方法的敏感性与特异性。结果证明,ELISA方法具有较好的敏感性(71.4%)。对ELISA检测为强阳性的奶牛进行细菌分离,并对5头结核菌分离阳性奶牛进行TST检测,结果有3头为TST阳性,2头可疑,显示出ELISA方法对严重感染牛的检测较TST具有更高的敏感性。由于TST与ELISA分别以细胞免疫与体液免疫为基础,两种检测方法结合应用可进一步提高牛结核病的检出率。     

Cloning and sequencing of badger (Meles meles) interferon gamma and its detection in badger lymphocytes

The European badger (Meles meles) has been identified as a reservoir for Mycobacterium bovis and is implicated in the maintenance and transmission of tuberculosis in cattle. There is a need for a sensitive test of M. bovis infection in badgers and the current serodiagnostic test used for this purpose has low sensitivity. As observed for other species, assay of interferon-gamma (IFNgamma) produced in response to M. bovis antigens is a more sensitive test of tuberculosis. With this objective in sight, we report the first step in the development of an ELISA for badger IFNgamma. The badger IFNgamma gene was cloned and sequenced and used to generate a specific polyclonal antibody to the cytokine. The gene sequence demonstrated regions that were conserved within the IFNgamma genes of other mammals. The badger sequence was most similar to the canine, showing similar structural organisation of the gene and 88% amino acid identity. Rabbits were immunised with DNA encoding badger IFNgamma and the resulting polyclonal antiserum demonstrated specificity for canine IFNgamma by immunoblot of a commercial recombinant canine IFNgamma. The antiserum was used to detect intracellular badger IFNgamma by flow cytometry analysis of badger lymphocytes stimulated with mitogen.     

Epidemiologic investigation of Mycobacterium bovis in a population of cats

OBJECTIVE: To determine whether cats exposed at a residence were infected with Mycobacterium bovis, whether the tuberculin skin test can identify cats infected with M bovis, and whether an ELISA could identify tuberculosis-infected cats. ANIMALS: 20 domestic cats exposed to a cat with laboratory-confirmed disseminated M bovis infection. PROCEDURE: Cats were administered a tuberculin skin test and monitored for 72 hours. Blood and fecal samples were collected. Cats were then euthanatized, and postmortem examinations were performed. Tissues were examined grossly and histologically for signs of mycobacteriosis. Pooled tissue samples and fecal samples were submitted for mycobacterial culture. Blood samples were examined for evidence of tuberculosis by use of a comparative ELISA. RESULTS: 4 cats had positive responses for the ELISA, and 2 cats had suspicious responses. All tuberculin skin tests yielded negative results. No gross or histologic lesions of tuberculosis were detected in any tissues, and mycobacteria were not isolated from tissues or feces obtained from the 20 cats. CONCLUSIONS AND CLINICAL RELEVANCE: All cats that had positive or suspicious responses for the ELISA were offspring of the cat with tuberculosis. Evidence of tuberculosis was not seen in other cats at the residence, the owner, or the attending veterinarian. The most likely source of tuberculosis for the infected cat was through the consumption of M bovis-infected wildlife carcasses or offal. Because M bovis is endemic in wildlife in northeastern Michigan, there is a risk of exposure to tuberculosis in companion animals, their owners, and attending veterinarians.