Single 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.

First results on small ruminant brucellosis and tuberculosis and caprine arthritis-encephalitis in El Salvador.

This paper reports a first-time study performed in El Salvador on the presence or absence of antibodies to three important animal diseases in small ruminants. The work was conducted in the west and central departments of the country, selecting 42 and 43 cantons with an existing sheep and goat population, respectively. Serum samples were collected from 396 sheep and 335 goats and tested for seropositivity to Brucella (B.) spp. The specimens from goats were also tested for antibodies to caprine arthritis-encephalitis (CAE) virus. Four (1%) sheep and none of the goats were seropositive by Rose Bengal test. All animals were negative by indirect ELISA (iELISA) for B. abortus. All animals were negative by iELISA for CAE. A total of 383 sheep and 330 goats underwent the single intradermal cervical tuberculin (SICT) test for tuberculosis. Seventy (18%) sheep and 43 (13%) goats reacted to the SICT test. Those reactors were subjected to the single intradermal comparative cervical tuberculin (SICCT) test, and one (0.3%) goat was deemed to be a positive reactor. No mycobacteria were diagnosed in concluding analyses, and further studies are considered necessary to determine the prevalence of the investigated diseases. Additionally, it is recommended that small ruminants should be included in the national eradication program on bovine brucellosis and tuberculosis to prevent potential reservoirs.

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.