Intradermal Cervical Tuberculin Test Research Articles

Field evaluation of the tuberculin skin test for the detection of Mycobacterium tuberculosis complex infection in communal goats (Capra hircus) in KwaZulu-Natal, South Africa

In South Africa, animal tuberculosis (TB) control programs predominantly focus on domestic cattle and African buffaloes (Syncerus caffer) despite increasing global reports of tuberculosis in goats (Capra hircus). Left undetected, Mycobacterium tuberculosis complex (MTBC) infected goats may hinder TB eradication efforts in cattle and increase zoonotic risk to humans. Since the publication of animal TB testing guidelines in 2018, prescribing the use of the tuberculin skin test (TST) for goats in South Africa by the Department of Agriculture, Land Reform, and Rural Development (DALRRD), there have been no published reports of any field application of the prescribed test criteria in goat herds. Therefore, this study aimed to evaluate the performance of these DALRRD guidelines using the single intradermal cervical tuberculin test (SICT) and the single intradermal comparative cervical tuberculin test (SICCT). Between October and December 2020, 495 goats from communal pastures of Kwa-Zulu Natal (KZN), where M. bovis infection has been identified in cattle and where cattle and goats cohabitate, were tested using the SICT and SICCT (M. bovis-exposed group). Additionally, 277 goats from a commercial Saanen dairy herd, with no history of M. bovis, were also tested (M. bovis-unexposed group). Estimated apparent prevalence of TST positive goats was determined based on published test interpretation criteria as described by DALRRD. When proportions of test-positive goats were compared between different DALRRD criteria, the ≥ 4 mm cut-off criterion for the SICCT resulted in the lowest proportion of positive results in the presumably uninfected group (1/277 positive in the unexposed group). The apparent prevalence of TB in the exposed group was estimated at 3.0% (95% CI: 1.7–4.9%), which is similar to previous reports of M. bovis prevalence in cattle from this area (6%). The detection of a significantly greater proportion of SICCT positive goats in the M. bovis-exposed group compared to the unexposed group suggests that MTBC infection is present in this population. Further investigations should be undertaken, in conjunction with confirmatory molecular tests, mycobacterial culture, and advanced pathogen sequencing to establish whether MTBC infection in domestic goats is a true under-recognized threat to the eradication of animal TB in South Africa.

Evaluation of ELISA and PCR in parallel to single intradermal cervical tuberculin test (SICT) for diagnosis of tuberculosis in buffaloes.

Bovine tuberculosis is an economically important disease with very high zoonotic potential. Single intradermal cervical tuberculin test (SICT) is considered a gold standard assay for the diagnosis of bovine tuberculosis. However, bovines especially buffaloes may produce a false negative result when the animal becomes cell-mediated immune (CMI) anergic in the advanced stage of the disease. In the present study, ELISA and PCR assays were successfully demonstrated to be useful in diagnosing tuberculosis especially in the CMI anergic buffaloes infected with Mycobacterium bovis. ELISA and PCR assays are able to detect 8.94% and 8.13%, respectively, more animals as positive in comparison to standard SICT assay in a selected population of 123 buffaloes. The moderate agreement between SICT and ELISA (k: 0.528; 0.249-0.807), a substantial agreement between SICT and PCR (k: 0.648; 0.364-0.931), and high agreement between ELISA and PCR (k: 0.856; 0.697-1.0) highlight that ELISA and PCR, if used in parallel with SICT, will provide better sensitivity over single assay. Reduction of false negative reactors may help in minimizing the zoonotic threat from bovine tuberculosis especially in disease endemic region where human and livestock interface is quite high.

Cost-effectiveness assessment of three components of the bovine tuberculosis surveillance system by intradermal tuberculin testing in French cattle farms by a scenario tree approach

In most officially bovine tuberculosis (bTB)-free countries, bTB has not been fully eradicated. Costly and time-consuming surveillance and control measures are therefore still in place to control this infection. An officially bTB-free status, both at the national and at the herd level, influences whether and when animals can be sold. Thus, this infection is still an economic issue, justifying measures towards its eradication. An evaluation of the cost-effectiveness of such measures would be highly useful, especially to optimise the costs of control measures and their adaptation to a local epidemiological context. We evaluated the cost-effectiveness of three mandatory surveillance protocols currently used in France by herd type (type of production, size, and turnover of the herd) under French field conditions. The first protocol (“strict”) implies the direct slaughter and post-mortem analyses of any intradermal cervical tuberculin test (ICT) reactor, and negative results to a second intradermal cervical comparative tuberculin test (ICCT) to regain bTB-free status of the herd. In the second protocol (“compliant quick-path”) bTB-free status can be regain if post-mortem analyses of reactors to the first ICT are negative. In the third protocol (“compliant slow-path”), ICCT-reactive animals are tested using the interferon gamma assay; the results of this test influence the path of further investigation. We built scenario trees for each of these protocols at the animal level. They allowed us to estimate herd sensitivity and the total cost of each protocol by herd type. The protocols could be ordered by decreasing herd sensitivity and cost, regardless of the herd type, as follows: strict protocol, compliant quick-path protocol, and compliant slow-path protocol. We calculated a cost-effectiveness index to evaluate the cost-effectiveness of each protocol. The strict protocol was never the most cost-effective, regardless of herd type, due to higher costs relative to the other protocols, despite better herd sensitivity. We found the compliant quick-path to be the most cost-effective protocol for big beef, big dairy, and mixed herds. The compliant slow-path was the most cost-effective for small-scale beef and dairy herds. All differences were significant. This comparison of the cost-effectiveness of the protocols by herd type could help authorities to choose the most suitable protocol in the investigation of suspected cases, depending on the herd type, but could be improved by accounting for important sociological data, such as the acceptability of the protocols.

Bovine tuberculosis is more prevalent in cattle owned by farmers with active tuberculosis in central Ethiopia

A case control study was conducted between October 2004 and April 2005 to determine the prevalence of bovine tuberculosis (BTB) in cattle in central Ethiopia relative to the tuberculosis status of their owners. A total of 174 farmers (87 with active tuberculosis and 87 with no active tuberculosis), and 1041 cattle (506 owned by farmers with active tuberculosis and 535 by farmers without active tuberculosis) were included. The comparative intradermal cervical tuberculin test was used in cattle while clinical symptoms, chest X-ray and Ziehl-Neelsen staining were used for the diagnosis of tuberculosis in the farmers. In addition, mycobacterial culture, biochemical tests, and drug susceptibility tests were performed for the identification Mycobacterium spp. from both humans and cattle. The prevalence of BTB was threefold higher (odds ratio [OR] = 4.2, 95% confidence interval [CI] = 2.79–6.2) in cattle owned by farmers with active tuberculosis (24.3%) than in those owned by farmers who did not have active tuberculosis (8.6%). Cattle owned by farmers with active tuberculosis were four times more likely to have tuberculosis than cattle owned by farmers with no active tuberculosis. Furthermore, cattle owners who consumed raw milk were at greater risk ( χ 2 = 14.1, P < 0.001, OR = 3.34) of having active tuberculosis than those who consumed boiled milk. Of the 42 human isolates, 31 (74%) were Mycobacterium tuberculosis, seven (16%) were Mycobacterium bovis while four (10%) were considered a typical mycobacteria on the basis of biochemical and drug sensitivity tests. Of the 11 cattle isolates, two (18%) were Mycobacterium tuberculosis, five (46%) Mycobacterium bovis, and four (36%) were atypical mycobacteria. The prevalence of tuberculosis was higher in cattle owned by farmers with active tuberculosis than in cattle owned by farmers who did not have active tuberculosis, which could suggest possible transmission of Mycobacterium spp. between cattle and their owners.

Evaluation of the 48 hour, 72 hour and 96 hour readings of tuberculin test for the screening of tuberculosis in cattle

In this study, a cattle farm with a history of tuberculosis was examined over a period of three years to determine the usefulness of reading tuberculin tests (single intradermal cervical tuberculin test (SICTT) and single intradermal comparative cervical tuberculin test (SICCTT)) at 48 hrs, 72 hrs and 96 hrs intervals in the diagnosis of tuberculosis. On the onset, SICTT was conducted on a total of 145 cattle, 52 (35.9%) of these were positive at 48 hours, 56 (38.6%) at 72 hours and 65 (44.8%) at 96 hours (X 2 =1.54, p=0.46). After one year, 171 cattle were screened using SICCTT, 10 (5.8%) animals were positive at 48 hours, 12 (7.0%) at 72 hours and 14 (8.2%) at 96 hours (X2=0.67, p=0.72). During the third test conducted almost one year after the second test, 136 cattle were screened using SICCTT, 13 (9.6%) were positive at 48 hours, 17 (12.5%) at 72 hours and 17 (12.5%) at 96 hours (X 2 = 0.68, p=0.71). With the pattern of this result, there may be need to review the policy which gave the 72 hr reading a preference over the 96 hr reading of tuberculin test. African Journal of Clinical and Experimental Microbiology Vol. 6 (3) 2005: 223-226

Field evaluation of the single intradermal cervical tuberculin test and the interferon-γ assay for detection and eradication of bovine tuberculosis in Spain

A field comparison of the interferon-γ (IFN-γ) assay and the single intradermal cervical tuberculin (SICT) test for the diagnosis of bovine tuberculosis was conducted. A total of 1136 cattle belonging to 85 herds placed in ‘Castilla y León’ (northwestern Spain) were chosen, and 21 of these herds were subjected to the diagnostic assays two or three times at intervals of at least 4 months. All the animals positive to any of the tests were slaughtered and tuberculosis was confirmed by culture isolation method (CIM) and further identification by means of PCR. Only 10.6% of cattle reacted with the bovine PPD in the SICT test, a percentage that increased to 12.8% in the IFN-γ assay. The sensitivity of the IFN-γ assay compared to CIM was shown to be higher (84.9%) than that of the SICT test (80.2%), but the combination of both tests offered the highest sensitivity (92.9%). The number of false positive reactors (those animals in which CIM was negative) was considerably higher for the IFN-γ assay than for the SICT test and, conversely, the number of false negative animals ( M. bovis isolation but negative immunological result) was higher for the skin test than for the interferon assay. In the herds tested twice, tuberculosis was eradicated after the second cycle of testing in 50%, and in 75% after the third cycle in herds tested three times. The combination of these two techniques instead of separately seems, therefore, to be useful in eradication programmes against bovine tuberculosis.

A case-control study on bovine tuberculosis in the Veneto Region (Italy)

A case-control study was undertaken to provide information about the role of some husbandry practices and farm characteristics in the epidemiology of bovine tuberculosis in the Veneto Region. Twenty-seven breeding herds where a positive result to the single intradermal cervical tuberculin test was confirmed by post-mortem examination were compared with seventy-four herds which had been free of the disease for at least three years. Epidemiological information was collected on farms. The factors taken into account in the study were chosen on the basis of their epidemiological plausibility and of the local livestock characteristics. Multiple logistic regression was applied to analyse the data. Factors identified as possibly involved in increasing the risk of bovine tuberculosis in the Veneto Region were the presence of mixed (dairy and beef) enterprises (OR=4.9, P=0.001) and of cattle purchase (OR=5.8; P=0.003). Other factors (such as herd size, housing system, summer mountain pasture, possible contact with wild animals, and indirect contacts with other herds) did not appear to significantly contribute to tuberculosis presence in this area. The results of this case-control study support the hypothesis that in the Veneto Region bovine tuberculosis infection is still associated with classical risk factors both (directly or indirectly) related to cattle movements.