Diagnosis of Bovine Tuberculosis by Comparative Intradermal Tuberculin Test, Interferon Gamma Assay and <i>esxB</i> (CFP-10) PCR in Blood and Lymph Node Aspirates

Abstract

Bovine tuberculosis (TB) is a chronic debilitating disease of huge economic importance due to loss in production, morbidity and mortality, and has a potential zoonotic threat. TB is endemic in India and has a worldwide prevalence, therefore, needing early diagnostic technique for the eradication of TB globally. Currently, compared to the eradication programme of TB in Medical sector, Veterinary sector is lagging behind though TB is one of the major zoonotic diseases prevalent in dairy animals and wildlife in India. With the "End TB" strategy by WHO in human, parallel measures for early diagnosis and culling has to be followed in case of animals for an overall successful eradication programme. The objective of this study is diagnosis of TB in cattle and buffaloes by using the cell-mediated immune response tests, i.e. Comparative Intradermal Tuberculin Test (CITT) and Interferon gamma (IFN-γ) assay, and Polymerase Chain Reaction (PCR) targeting esxB gene (CFP-10 protein) and to compare their diagnostic capabilities. This study was carried out in 202 dairy cattle and buffaloes from an organized dairy farm, where almost all of the animals appeared clinically healthy. We found that, the combined use of both CITT and IFN-γ assay lead to more accurate diagnosis of TB, although IFN-γ assay was more specific than CITT. However, esxB PCR showed almost similar sensitivity to IFN-γ assay and may be used as a fast alternative method for the diagnosis of bovine TB from blood samples.

Review on Bovine Tuberculosis: An Emerging Disease Associated with Multidrug-Resistant Mycobacterium Species

“…In 1882, Koch discovered the tubercle bacillus of Mycobacterium tuberculosis ( Mtb ), the causative agent of human TB [ 2 ], whilst Smith in 1898, identified M. bovis as a different species from Mtb [ 3 ]. Bovine TB has a marked economic importance because of loss in productivity, morbidity, and mortality, in addition to the potential zoonotic threat [ 4 ]. The surveillance costs also have immense economic importance.…”

“…Besides tissue samples, many PCR assays had been performed on blood and milk samples such as the Mataragka et al study, which illustrated that PCR can be used as an early and sensitive indicator method to detect infection in pooled milk samples collected from the aged animals of a dairy farm, which could support TST monitoring and improve bTB control [ 114 ]. In addition, Brahma et al reported a similar sensitivity of PCR targeting CFP-10 protein to that of IGRA and concluded that it may be used as a fast, alternative method for bTB diagnosis from blood samples [ 4 ]. Elsohaby et al reported a difference between the PCR estimates of M. bovis in both blood and milk in dairy cattle, where the sensitivity of PCR conducted on blood and milk samples was 53–95% and 1–60% while its specificity was 95–100% and 43–99% for each sample, respectively [ 72 ].…”

“…The authors attributed these differences to the type of sampling, that largely affect the PCR sensitivity and specificity estimates. However, further studies about bacteremia and the time of dissemination of M. bovis in blood stream is needed to detect the proper sampling time because most of TST and IGRA reactor animals failed to be detected by PCR in blood samples [ 4 ]. Despite the high risk of disseminated infection of M. bovis , bacteremia has been assumed to be rare in cattle [ 115 ].…”

Specific identification of Mycobacterium bovis by Loop-Mediated Isothermal Amplification (LAMP) targeting the Region of Difference 12 (RD12) of the M. tuberculosis complex

“…Hence, early detection of BTB is pivotal to ensure effective control of any outbreak, and minimize the economic impact on farms [7] . The gold standard methods for BTB diagnosis are based on cellular immunity through the intradermal tuberculin skin test (TST) and/or the interferon-gamma release assay (IGRA) [8] .…”

Histopathological and Molecular Investigation of Natural Cases of Bovine Tuberculosis Infection in Cattle

“…TST cannot be repeated for at least 60 days because of systemic desensitization caused by the injection of tuberculin. The use of Comparative Intradermal Tuberculin Test (CITT) as a diagnostic test to overcome the problem of false positive reactions of the Single Intradermal test in India is restricted due to unavailability of avian tuberculin (Brahma et al, 2019). In-vitro blood IFN-γ assay measures the cell-mediated immune response of M. bovis infected animals (Reuss, 1995) with the limitation of non-specific responses in a young animal, high logistic demand (culture start is required within 24 hours after blood collection), the requirement of welltrained personnel (Ramos et al, 2015).…”