Tuberculosis in cattle and its control: limitations to the use of the interferon-gamma assay in attested herds (original) (raw)
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Australian Veterinary Journal, 1991
An extensive field comparison of the gamma interferon (IFN-Y) assay and the single intradermal tuberculin test for the diagnosis of bovine tuberculosis was conducted in Australia. The speciflclty of the iFNy assay was determined by testing more than 6000 cattle from tuberculosis-free herds and varied from 96.2% to 98.1%, depending on the cut-off point chosen to define a positive reactor. For the sensitivity trial, cattle from herds being depopulated because of bovine tuberculosis were examined with both assays. The sensltlvlty of the IFN-y assay was shown to be signlflcantly higher than the single intradermai tuberculin test and varied from 76.8% to 93.6% depending on the method of Interpretation. A maximum overall sensitivity of 95.2% was obtained by testing with the IFNy and the tuberculin test in parallel. The superior sensitivity of the iFNyassay and the ability to adjust the sensitivity of the system depending on the task involved, will provide the Australian Tuberculosis Eradication Campaign with a valuable additional test to enable it to accomplish its goals. . 3002 cattle (Rothel et d 1990) and in a limited field trial using cattle from infected herds ). In these studies the IFN-y assay was found to be more sensitive than the SID test, but too few infected cattle were available to establish this with confidence. This paper describes extensive field trials in both infected herds and herds known to be free of tuberculosis to establish the sensitivity and specificity of the IFN-y assay.
Research in Veterinary Science, 2006
The early, preclinical stages of bovine TB can be detected in live animals by the use of tests of cellular immunity (the skin, c-interferon and lymphocyte transformation tests). Tests of humoral (antibody) immunity, Mycobacterium bovis PCR probes on early tissue cultures or live cattle specimens, and tests based on ‘‘electronic nose’’ technology have been developed more recently. The key measure of diagnostic test accuracy is the relationship between sensitivity and specificity, which determines the false-positive and false-negative proportions. None of the tests currently available for the diagnosis of bovine TB allow a perfectly accurate determination of the M. bovis infection status of cattle. Although various factors can reduce the sensitivity and specificity of the skin tests, these remain the primary ante mortem diagnostic tools for TB in cattle, providing a cost-effective and reliable means of screening entire cattle populations. Despite the inescapable limitations of existing diagnostic tests, bovine TB has been effectively eradicated from many developed countries and regions with the implementation of sound programmes of regular tuberculin skin testing and removal of reactors, coupled with slaughterhouse surveillance for undetected infections, repeat testing and culling of infected herds, cattle movement restrictions to prevent introduction of infected animals and occasional slaughter of entire herds with intractable breakdowns. This is likely to remain the mainstay of bovine TB control programmes for the foreseeable future. Additionally, newer ancillary in vitro diagnostic assays are now available to TB control programme managers to supplement the skin tests in defined circumstances according to the specific disease situation in each country or region. The strategic deployment of ancillary in vitro tests alongside the primary skin tests has enhanced the detection of M. bovis-infected cattle and reduced the number of animals slaughtered as false positives.
Research in Veterinary Science, 2000
The gamma interferon (IFN-γ) test was evaluated for its ability to diagnose bovine tuberculosis in cattle that 8 to 28 days previously had a positive caudal fold skin test. The sensitivity of the test was determined in a group of 163 Mycobacterium bovis-infected cattle from 21 herds. The specificity was estimated in a group of 213 cattle which had reacted to a caudal fold test, but were from 82 herds that had no evidence of infection with M bovis. The sensitivity and specificity of the IFN-γ test was 85 and 93 per cent respectively. No significant differences in the sensitivity and specificity of the test were observed between blood samples that were cultured on the day of collection and those cultured the day after collection. These findings support the use of the IFN-γ test as a practical serial test that can be used to complement the caudal fold skin test.
Journal of Applied Microbiology, 1999
GONZÁ LEZ LLAMAZARES, O.R., GUTIÉ RREZ MARTÍN, C.B., ARANAZ MARTÍN, A., LIÉ BANA CRIADO, E., DOMÍNGUEZ RODRÍGUEZ, L. AND RODRÍG U EZ FE R RI , E . F. 1999. Of 1479 cattle from herds in Northwestern Spain previously diagnosed as tuberculosis (TB) positive, 218 animals which gave a positive tuberculin or interferon-g reaction were examined at the slaughterhouse. Medial retropharyngeal and caudal mediastinal lymph nodes, and any tissues containing lesions suspected to be tuberculous, were removed and submitted to the laboratory. Three techniques for diagnosis of TB were used: post mortem examination (PME), smear staining by means of auramine O method (AOM), and culture isolation in Coletsos and Lowenstein-Jensen media followed by confirmation of M. tuberculosis complex organisms using PCR (CIM-PCR). Only 123 (29·9%) of the 412 samples collected showed typical tuberculous lesions. Confirmed M. tuberculosis complex organisms were isolated in 144 cases, 114 of which were from tissues showing lesions (success rate of 92·8%). Smears were found positive in 113 cases, 96 of which came from lesions suspected to be tuberculous (success rate of 78·0%). The sensitivities of CIM-PCR compared with those of PME and AOM were 92·7% and 85·7%, respectively. Statistical analysis revealed that PME and AOM are good indicators of the presence of M. tuberculosis complex organisms in tuberculinor interferon-g reacting cattle.
Veterinary Immunology and Immunopathology, 2004
The strategic use of the gamma-interferon (IFN-g) assay (Bovigam 1 ) can provide a means for the early identification of Mycobacterium bovis infected cattle, thus ensuring their removal from an infected herd. It has been reported that performance of the test can be influenced by various factors including a recent tuberculin skin test and the length of delay between collection and processing of blood samples. In this study, single intradermal comparative tuberculin test (SICTT) reactor and non-reactor cattle were recruited from herds infected with M. bovis and grouped according to their SICTT responses. Group 1 comprised reactor cattle selected on the basis of their SICTT response to PPD-bovine (purified protein derivative of tuberculin) exceeding that of PPD-avian by at least 12 mm. Group 2 animals were selected from herds undergoing routine surveillance for bovine tuberculosis and contained standard SICTT reactor cattle (PPD-bovine exceeding that of PPD-avian by at least 4 mm) and non-reactors. We investigated the effects of the SICTT on the assay results by measuring the in vitro IFN-g responses of Group 1 reactor cattle at time intervals pre-and post-skin test. No significant differences were measured in the IFN-g responses of the reactor animals to PPD-bovine and PPD-avian for up to 65 days. To investigate if a delay in processing of blood affected the performance of the assay, we compared results using duplicate blood samples from Group 1 and Group 2 cattle stimulated with PPD antigen at 8 h and at 24 h after collection. In both groups of animals the mean optical density (OD) values of the assay at 24 h post-collection were significantly lower than those at 8 h. Our results demonstrated that a delay in processing of the blood samples from cattle subjected to routine surveillance could significantly impact on the outcome of the IFN-g assay resulting in a change of the IFN-g status of the animals. #
2023
Background and Aim: Bovine tuberculosis (bTB) is an infectious disease of cattle, mainly caused by Mycobacterium bovis. This study aimed to evaluate the efficacy of the interferon-gamma (IFN-γ) assay and single-intradermal comparative tuberculin test (SICTT) in detecting bTB. Materials and Methods: In an earlier study, 150 positive, 83 inconclusive, and 480 negative animals from 24 cattle herds were screened using SICTT. From these groups, 125 positive, 17 inconclusive, and six negative animals were subsequently verified using the IFN-γ assay. Single-intradermal comparative tuberculin test outcomes were interpreted according to standard guidelines, whereas blood samples were collected and stimulated with purified protein derivatives. Sandwich enzyme-linked immunosorbent assay was used to measure secreted IFN-γ. Concordant and Bayesian latent class analyses were performed to evaluate test performance. Results: Results from the IFN-γ assay revealed that 83.2%, 64.7%, and 16.67% of the animals were positive in the SICTTpositive, inconclusive, and negative animal categories, respectively. Sensitivity (SE) and specificity (SP) of SICTT were 83.9% (95% confidence interval [CI]: 77.4-90.1) and 95.7% (95% CI: 86.9-99.7), respectively. Sensitivity and SP for the IFN-γ assay were 78.9% (95% CI: 71.9-85.4) and 83.9% (65.9-95.9), respectively. The use of both tests in parallel increases the SE of bTB detection (~94%), compared with SICTT alone. Conclusion: Use of the IFN-γ assay with SICTT in parallel, predominantly on cattle demonstrating an inconclusive SICTT outcome, boosts bTB detection rate in low resource settings.
Journal of Wildlife …, 2010
In 1996, the Hook Lake Wood Bison Recovery Project was initiated to establish a small, disease-free, captive, bison-breeding herd. Founders originated from wild bison herds in the Slave River Lowlands in northern Canada, which, like other bison herds in and around Wood Buffalo National Park, are endemically infected with bovine tuberculosis (caused by Mycobacterium bovis) and brucellosis (caused by Brucella abortus). After 9 yr of apparent disease freedom, tuberculosis was detected within the captive herd, leading to complete depopulation. This study examined the performance of antemortem tuberculosis diagnostic tests used during the project. Performances of the caudal-fold test, fluorescent polarization assay, multiantigen print immunoassay (MAPIA), and the rapid test (RT) were assessed by estimating sensitivity, specificity, positive predictive value, and negative predictive value for each test. Kappa values measuring agreement between tests were calculated. Overall, the tests did not differ with respect to sensitivities and specificities, which ranged from 50% to 92% and from 34% to 100%,respectively. The MAPIA tended to show high sensitivity, and there was significant agreement only between the MAPIA and RT. Serum collected from infected animals at slaughter produced highly variable results on the different assays, and one infected bison was negative on all antemortem tests. The results of this analysis suggest use of multiple antemortem tests in parallel, particularly those incorporating multiple antigens, to optimize sensitivity in detecting bovine tuberculosis in bison. However, as demonstrated in this herd, even a seemingly optimal antemortem testing regimen can fail to detect M. bovis–infected individuals.
Veterinary Research, 2006
The intradermal tuberculin (IDTB) test and the interferon-gamma (IFN-γ) assay are used worldwide for detection of bovine tuberculosis in cattle, but little is known about the effect of co-infecting agents on the performance of these diagnostic tests. This report describes a field trial conducted in a cattle herd with dual infection (bovine tuberculosis and paratuberculosis) during 3.5 years. It has been based on a strategic approach encompassing serial parallel testing (comparative IDTB test, the IFN-γ assay and serology of paratuberculosis) that was repeated 8 times over the period, and segregation of animals into two herds. The IDTB test detected 65.2% and the IFN-γ test detected 69.6% of the Mycobacterium bovis culture-positive cattle. However, the IDTB test performed better during the first part of the trial, while the IFN-γ test was the only method that detected infected animals during the following three samplings. The number of false positive reactors with the IDTB and/or the IFN-γ tests was remarkably high compared to other reports, and could be caused by cross-reactivity with M. avium subsp. paratuberculosis. Also, the M. bovis isolates from cattle and wildlife from the same property were characterised using molecular techniques to disclose an epidemiological link. The IDTB test may not be appropriate to eradicate bovine tuberculosis in herds with dual mycobacterial infections. This report highlights the need to use several diagnostic techniques for the accurate detection of M. bovis infected animals in these herds.
Evaluation of Three Commercial Interferon-γ Assays in a Bovine Tuberculosis Free Population
Frontiers in Veterinary Science, 2021
The interferon-γ assay has been used worldwide as an ancillary test for the diagnosis of bovine tuberculosis (bTB). This study aimed to describe, based on the bTB-free status in Switzerland, the difference of applying a more stringent cutoff point of 0.05 compared with 0.1 for bTB surveillance. Moreover, the effect of time between blood collection and stimulation, culture results, optical density values, and the influence of testing different breeds were evaluated. Blood samples from a total of 118 healthy cows older than 6 months were tested with three commercial interferon-gamma assays. To confirm the bTB-free status of the tested animals and to investigate potential cross-reactions with nontuberculous mycobacteria, pulmonary and abdominal lymph nodes in addition to ileal mucosa from each cattle were used for the detection of viable Mycobacteria spp. by specific culture. Significant differences regarding the proportion of false-positive results between the two Bovigam tests and between Bovigam 2G and ID Screen were found. Samples analyzed with Bovigam 2G were 2.5 [95% confidence interval (CI) 1.6-3.9] times more likely to yield a false-positive test result than samples analyzed with Bovigam TB. Similarly, the odds ratio (OR) for testing samples false-positive with ID Screen compared with Bovigam TB was 1.9 (95% CI 1.21-2.9). The OR for testing false-positive with ID Screen compared with Bovigam 2G was less to equally likely with an OR of 0.75 (95% CI 0.5-1.1). When using a cutoff of 0.05 instead of 0.1, the OR for a false-positive test result was 2.2 (95% CI 1.6-3.1). Samples tested after 6 h compared with a delayed stimulation time of 22-24 h were more likely to yield a false-positive test result with an OR of 3.9 (95% CI 2.7-5.6). In conclusion, applying a more stringent cutoff of 0.05 with the Bovigam 2G kit generates a questionable high number of false-positive results of one of three tested animals. Furthermore, specific breeds might show an increased risk to result false-positive in the Bovigam 2G and the ID Screen assays.