Single Intradermal Test Research Articles

Comparative analysis of tuberculin and defined antigen skin tests for detection of bovine tuberculosis in buffaloes (Bubalus bubalis) in Haryana state, India

BackgroundBovine tuberculosis (bTB) is a chronic disease that results from infection with any member of the Mycobacterium tuberculosis complex. Infected animals are typically diagnosed with tuberculin-based intradermal skin tests according to World Organization of Animal Health which are presently in use. However, tuberculin is not suitable for use in BCG-vaccinated animals due to a high rate of false-positive reactions. Peptide-based defined skin test (DST) antigens have been identified using antigens (ESAT-6, CFP-10 and Rv3615c) which are absent from BCG, but their performance in buffaloes remains unknown. To assess the comparative performance of DST with the tuberculin-based single intradermal test (SIT) and the single intradermal comparative cervical test (SICCT), we screened 543 female buffaloes from 49 organized dairy farms in two districts of Haryana state in India.ResultsWe found that 37 (7%), 4 (1%) and 18 (3%) buffaloes were reactors with the SIT, SICCT and DST tests, respectively. Of the 37 SIT reactors, four were positive with SICCT and 12 were positive with the DST. The results show that none of the animals tested positive with all three tests, and 6 DST positive animals were SIT negative. Together, a total of 43 animals were reactors with SIT, DST, or both, and the two assays showed moderate agreement (Cohen’s Kappa 0.41; 95% Confidence Interval (CI): 0.23, 0.59). In contrast, only slight agreement (Cohen’s Kappa 0.18; 95% CI: 0.02, 0.34) was observed between SIT and SICCT. Using a Bayesian latent class model, we estimated test specificities of 96.5% (95% CI, 92–99%), 99.7% (95% CI: 98–100%) and 99.0% (95% CI: 97–100%) for SIT, SICCT and DST, respectively, but considerably lower sensitivities of 58% (95% CI: 35–87%), 9% (95% CI: 3–21%), and 34% (95% CI: 18–55%) albeit with broad and overlapping credible intervals.ConclusionTaken together, our investigation suggests that DST has a test specificity comparable with SICCT, and sensitivity intermediate between SIT and SICCT for the identification of buffaloes suspected of tuberculosis. Our study highlights an urgent need for future well-powered trials with detailed necropsy, with immunological and microbiological profiling of reactor and non-reactor animals to better define the underlying factors for the large observed discrepancies in assay performance, particularly between SIT and SICCT.

A decade of tuberculosis eradication programs in the Mediterranean water buffalo (Bubalus bubalis) in South Italy: Are we heading toward eradication?

The water buffalo (Bubalus bubalis) is susceptible to bovine tuberculosis (TB), which receives increased attention in areas where buffalo breeding is prevalent, such as in Southern Italy, especially in the Campania region, where 70% of the buffalo stock is bred. Since 2012, TB testing in buffalo herds has been conducted using the Single Intradermal Test (SIT), with the Comparative Intradermal test (CIT) used in cases of inconclusive results. From 2012 to 2016, the interferon-gamma (IFN-γ) test was occasionally employed experimentally in herds with TB outbreaks to expedite eradication efforts. A local TB eradication program was implemented in officially TB-free buffalo herds between 2017 and 2019. This program involves initial screening with SIT, followed by confirmatory tests, including CIT and IFN-γ, for positive reactions. Since June 2019, the IFN-γ test has replaced the CIT in officially TB-free herds upon positive SIT reactions. Additionally, in suspected and confirmed TB-outbreak herds, the IFN-γ test was used at the discretion of the competent authority. Between 2017 and 2019, approximately 295,000 buffaloes in Campania were screened annually with in vivo tests provided by TB eradication programs. During this period, 32,040 animals from 855 herds were tested using the IFN-γ test and 4,895 tested positive. Since 2020, the use of IFN-γ testing has increased, and has become a prerequisite for the acquisition of TB-free status and is being systematically applied for TB outbreak-extinction procedures. The test was performed in all breeding buffaloes in cases of doubtful SIT results in TB-free herds and when TB lesions are detected at slaughter in animals from TB-free herds. This combined approach helped detect more TB outbreaks, and thereby led to a reduction in the TB prevalence and incidence rates. By 2022, the prevalence had decreased to 1.56%, and the incidence had decreased to 0.73%, after the increased use of the IFN-γ test. This study highlights the effectiveness of implemented strategies in reducing TB in this region. Overall, the data demonstrate the successful impact of TB eradication measures and surveillance activities in reducing bubaline TB prevalence and incidence in the Campania region.

Can more information be extracted from bovine TB skin test outcomes to inform animal risk management? A retrospective observational animal-level study

Continual tailoring of control programmes of endemic pathogens during long-term eradication campaigns requires detailed analysis of surveillance data to inform evidence-based policy. Bovine tuberculosis is a disease where long-term control and eradication programs are in train in several countries. The primary diagnostic tool, the intradermal tuberculin test, used to identify infected animals can be interpreted using different criteria and cut-offs, facilitating flexibility in its use as a basis to inform interventions.We investigated the comparative risk of animals failing a single intradermal comparative tuberculin test (SICTT) based on their previous tuberculin test result following a higher risk test-type (reactor retest of an infected herd). The study was a retrospective cohort design, and the primary exposure was the test status following a reactor retest classified as mutually exclusive categories based on bovine and avian tuberculin reactions: standard interpretation inconclusive (Sdi), severe interpretation inconclusive (Svi), single intradermal test (SIT) reactors (SITr), SIT inconclusive (SITi), avian tuberculin reactors (Ar), and test negative animals. Random effects multivariable logistic regression was used to investigate future risk. Cross-validation and downscaling was used to explore model performance. Alternate models with differing outcome test types were also explored.The models were trained on 844,207 observations from June 2018 to June 2021. Sdi, Svi, SITr, SITi and Ar were associated with the following odds ratios 12.242 (95 %CIs: 5.236–28.625; p < 0.001), 4.101 (95 %CIs: 3.423–4.913; p < 0.001), 2.503 (95 %CIs: 1.878–3.338; p < 0.001), 1.741 (95 %CIs: 1.195–2.538; p = 0.004) and 1.065 (95 %CIs: 0.833–1.361; p = 0.616) for failing the next test, respectively. High model performance was achieved with inclusion of random effects for both training and test evaluation datasets (AUC: 0.94; Balanced accuracy: 0.84), but fixed-effects only predictions exhibited moderate performance (AUC: 0.70; Balanced accuracy: 0.69). This reflects that 55 % of the risk of test failure relates to between herd heterogeneity based on intra-class correlation, while controlling for fixed effects. Other factors that were associated with increasing risk included age (older cohorts were at greater risk than the youngest cohort), breakdown history of the herd (greater number of breakdowns prior to the study period), and the time between exposure test and outcome test.These results provide further evidence to inform risk-based management policies for TB, including the removal of Sdi animals in higher risk situations, supplementary testing of cattle based on tuberculin responses and the provision of risk management advice to herd owners. The results characterise the future animal-level risk posed by Svis and suggest this risk may require policy led interventions.

Comparative diagnosis of bovine tuberculosis using single intradermal cervical tuberculin technique, conventional methods, enzyme-linked immunosorbent assay, and the gamma-interferon assay.

Background and Aim:Bovine tuberculosis (TB) is a zoonotic disease that causes huge economic losses. This study aimed to compare the result obtained from the single intradermal test, conventional methods (culture and microscopy), gamma-interferon (IFN-γ) assay, and indirect enzyme-linked immunosorbent assay (ELISA) to diagnose bovine TB.Materials and Methods:This study evaluated 2913 animals from milk farms in Cairo, El-Sharkia, and El-Qalyubia Governorates by single intradermal cervical tuberculin technique (SICTT), ELISA, and IFN-γ assay.Results:Of the 2913 dairy cows surveyed, 3.7% yielded positive results. Culture prepared samples on Lowenstein-Jensen and Middlebrook 7H10 agar media yielded 52 (1.85%) isolates of Mycobacterium spp. from 2805 milk samples that yielded negative tuberculin reactions and 56 (51.85%) isolates of Mycobacterium spp. were recovered from 108 lymph node samples from positive cases. ELISA analysis of the sera of 108 positive SICTT reactors revealed that 94 (87.03%) and 97 (89.81%) animals were positive for bovine purified protein derivative (PPD-B) antigen and commercial polypeptide antigen, respectively. IFN-γ assays were performed on whole blood samples collected from positive SICTT reactors and showed that 103 (95.37%) animals were positive.Conclusion:M. tuberculosis complex may be isolated from raw milk and not all infected animals shed mycobacterial bacilli in their milk. The use of polypeptide antigen in ELISA provides better diagnostic efficacy than PPD-B antigen. The IFN-γ assay is more sensitive than both SICTT and ELISA. It should be used in parallel with SICTT to allow the detection of more positive animals before they become a source of infection to other animals and humans.

A Defined Antigen Skin Test That Enables Implementation of BCG Vaccination for Control of Bovine Tuberculosis: Proof of Concept.

In most low- and middle-income countries (LMICs), bovine tuberculosis (bTB) remains endemic due to the absence of control programs. This is because successful bTB control and eradication programs have relied on test-and-slaughter strategies that are socioeconomically unfeasible in LMICs. While Bacillus Calmette–Guérin (BCG) vaccine-induced protection for cattle has long been documented in experimental and field trials, its use in control programs has been precluded by the inability to differentiate BCG-vaccinated from naturally infected animals using the OIE-prescribed purified protein derivative (PPD)-based tuberculin skin tests. In the current study, the diagnostic specificity and capability for differentiating infected from vaccinated animals (DIVA) of a novel defined antigen skin test (DST) in BCG-vaccinated (Bos taurus ssp. taurus x B. t. ssp. indicus) calves were compared with the performance of traditional PPD-tuberculin in both the skin test and in vitro interferon-gamma release assay (IGRA). The IFN-γ production from whole blood cells stimulated with both PPDs increased significantly from the 0 week baseline levels, while DST induced no measurable IFN-γ production in BCG-vaccinated calves. None of the 15 BCG-vaccinated calves were reactive with the DST skin test (100% specificity; one-tailed lower 95% CI: 82). In contrast, 10 of 15 BCG-vaccinated calves were classified as reactors with the PPD-based single intradermal test (SIT) (specificity in vaccinated animals = 33%; 95% CI: 12, 62). Taken together, the results provide strong evidence that the DST is highly specific and enables DIVA capability in both skin and IGRA assay format, thereby enabling the implementation of BCG vaccine-based bTB control, particularly in settings where test and slaughter remain unfeasible.

A Retrospective Study on Bovine Tuberculosis in Cattle on Fiji: Study Findings and Stakeholder Responses.

Bovine tuberculosis (bTB) is globally significant due to its impacts on cattle production. A Brucellosis and Tuberculosis Eradication and Control (BTEC) program commenced in Fiji during the 1980's and has since been sustained by government funding and industry cooperation. A retrospective study of bTB data obtained during the Fiji BTEC program from 1999 to 2014 was undertaken at the University of Sydney with support from the Government of Fiji. It confirmed that bTB is well-established in dairy cattle farms in Naitasiri and Tailevu provinces of Central Division on the main island of Viti Levu, and suggested that the disease is present among cattle on farms in all or most provinces across three (Central, Northern, Western) of the four divisions in the country. It was evident that despite sustained efforts, disease reduction and containment was not being achieved. Reasons contributing to this situation included the appropriateness of the protocol for conduct of the single intradermal test (SID) in cattle, absence of regular quality assurance training of BTEC field staff, lack of standard procedures for bTB data collation and evaluation, unregulated cattle movements and the presence of stray cattle. The Fiji Ministry of Agriculture responded proactively to these findings by implementing revision to the use of the SID in cattle and refresher training for staff along with the Biosecurity Authority of Fiji who implemented cattle movement restriction. A subsequent apparent outbreak of bTB in some farms due to increased detection by the new test protocol raised concerns for the local dairy industry. To clarify the status and extent of bTB infection and the challenges faced by the industry, a stakeholder forum was held in May 2017, and a new BTEC strategy was formulated and endorsed by stakeholders. bTB remains a focus for cattle disease control by the government of Fiji. This case study highlights the challenges for bTB control in Fiji and underlines the importance of technical and social considerations to achieve success in disease control.

Oral Vaccination with Heat-Inactivated Mycobacterium bovis Does Not Interfere with the Antemortem Diagnostic Techniques for Tuberculosis in Goats.

Vaccination against tuberculosis (TB) is prohibited in cattle or other species subjected to specific TB eradication campaigns, due to the interference that it may cause with the official diagnostic tests. However, immunization with a heat-inactivated (HI) Mycobacterium bovis vaccine via the oral route has been suggested to overcome this issue. In this study, the main goal was to assess the interference of the HI vaccine by different routes of administration using a previous vaccination and re-vaccination (boosting) protocol. TB-free kid goats were divided into three groups: oral (n = 16), intramuscular (IM; n = 16), and control (n = 16). Results showed that there was a significant difference in the percentage of animals positive to the single intradermal test (SIT) and blood based interferon-gamma release assay (IGRA) caused by vaccination when performed in the IM group compared to the oral group (p < 0.001). Nevertheless, no positivity to the SIT or IGRA test was observed in orally vaccinated goats regardless of the different interpretation criteria applied. None of the groups presented positive antibody titers using an in-house ELISA and samples collected 2 months after the boost. These results suggest the potential usefulness of the HI vaccine by the oral route in goats to minimize the interference on diagnostic tests (skin and IGRA tests) and reducing the necessity of defined antigens to replace the traditional purified protein derivatives for diagnosis. Finally, the results pave the way to future efficacy studies in goats using different routes of HI vaccination.

Tuberculosis Detection in Paratuberculosis Vaccinated Calves: New Alternatives against Interference.

Paratuberculosis vaccination in cattle has been restricted due to its possible interference with the official diagnostic methods used in tuberculosis eradication programs. To overcome this drawback, new possibilities to detect Mycobacterium bovis infected cattle in paratuberculosis vaccinated animals were studied under experimental conditions. Three groups of 5 calves each were included in the experiment: one paratuberculosis vaccinated group, one paratuberculosis vaccinated and M. bovis infected group and one M. bovis infected group. The performance of the IFN-gamma release assay (IGRA) and the skin test using conventional avian and bovine tuberculins (A- and B-PPD) but also other more specific antigens (ESAT-6/CFP10 and Rv3615c) was studied under official and new diagnostic criteria. Regarding the IGRA of vaccinated groups, when A- and B-PPD were used the sensitivity reached 100% at the first post-challenge sampling, dropping down to 40–80% in subsequent samplings. The sensitivity for the specific antigens was 80–100% and the specificity was also improved. After adapting the diagnostic criteria for the conventional antigens in the skin test, the ability to differentiate between M. bovis infected and non-infected animals included in paratuberculosis vaccinated groups was enhanced. Taking for positive a relative skin thickness increase of at least 100%, the single intradermal test specificity and sensitivity yielded 100%. The comparative intradermal test was equally accurate considering a B-PPD relative skin increase of at least 100% and greater than or equal to that produced by A-PPD. Using the specific antigens as a proteic cocktail, the specificity and sensitivity reached 100% considering the new relative and absolute cut-offs in all experimental groups (Δ≥30% and Δmm ≥ 2, respectively). Results suggest that the interference caused by paratuberculosis vaccination in cattle could be completely overcome by applying new approaches to the official tuberculosis diagnostic tests.

A preliminary assessment of new bovine and avian tuberculin in cattle by intra-dermal tests and whole blood interferon gamma assay

The present study reports ante-mortem diagnosis of bovine tuberculosis employing tuberculin test using a new tuberculin PPDB (M. bovis, 3/86) and interferon gamma assay in cattle whole blood culture stimulated using a commercial bovine IFN- γ assay kit. Dairy cattle (87) categorized in groups A, B and C were tested using tuberculin test and gamma interferon (IFN-γ). Fresh batches of bovine PPD (from M. bovis 3/86) and avian PPD (M. avium N–17) were prepared and were standardized by conforming to sterility, safety and potency. For tuberculin testing cervical single intradermal test (SIT) and caudal fold test (CFT) were performed using tuberculins at concentration of 1mg/ml and at the concentration of 0.3mg/ ml as a stimulating antigens in IFN-γ test. Out of 80 cattle (group A + B), 44 (55%) were reactor to tuberculin, 21 (26.25%) non reactor and 15 (18.75%) were inconclusive animals and by IFN-γ test 36 (45%) were M. bovis positive, 10 (12.5%) negative, 13 (16.25%) inconclusive and 21 (26.25%) were M. avium positive animals. In group C (not tuberculin tested) only 4 (57.14%) out of 7 cattle were positive. Relative sensitivity of IFN-γ test (63.88%) was higher than the tuberculin test (52.27%). Our study indicated that skin tests (CFT and SIT) and IFN-γ test can be used for successful control and eradication of bovine tuberculosis as IFN-γ test had higher sensitivity.

Review on Zoonotic Importance of Bovine Tuberculosis and Its Control

Bovine tuberculosis is a chronic infectious zoonotic disease of domestic animals and humans. It is characterized by formation of granulomas in tissue especially the lungs, lymph nodes, liver, intestines and the kidneys. Mycobacterium bovis is the main etiological agent of BTB (Bovine tuberculosis) which is an acid fast staining bacterium due to waxy substance (mycolic acid) present in its bacterial cell wall. The bacteria can be transmitted by both aerogenous and enterogenous routes. In Ethiopia bovine tuberculosis is endemic and mostly transmitted to humans through ingestion of unpasteurized contaminated milk and contact with infected animals. Disease causes development of miliary tubercular lesions, chronic cough, obstructions of air passages and alimentary tract or blood vessels and enlargement of lymph nodes. A spectrum of Cell-Mediated Immune responses (CMI) predominate infection, projecting the role of macrophages and T-cell populations. In advanced stage, there is increased humoral response. Tuberculinization test, single intradermal test and comparative intradermal test, is the valuable delayed type hyper sensitivity test used for diagnosing TB in live animal, and used in TB eradication and for international trade. Vaccination of calves with attenuated bovine-strain of tuberculosis bacterium, known as Bacillus of Calmette and Guerin (BCG) and testing and culling are important measure in BTB control and prevention endemic area like Ethiopia. It is important to pasteurize milk before human consumption to reduce public health risk.

Comparison of Single Intradermal Test, Gamma Interferon Assay and Indirect ELISA for the Diagnosis of Tuberculosis in a Dairy Farm

Comparison of Single Intradermal Test, Gamma Interferon Assay and Indirect ELISA for the Diagnosis of Tuberculosis in a Dairy Farm

Evaluation of single intra-dermal test and commercial ELISA for diagnosis of paratuberculosis in Indian cattle population

Between May 2008 and March 2009, serum samples (1,170) were collected from indigenous purebred and crossbred cattle housed in 15 organized farms located across seven states of India. These sera were tested for the presence of antibodies against Mycobacterium avium paratuberculosis (Map). After blood collection, all these animals were screened for paratuberculosis by single intra-dermal injection of Johnin protein purified derivatives. The Hui-Walter, no gold standard approach under the assumption of conditional independence was used to estimate sensitivity and specificity of these 2 tests and the prevalence of paratuberculosis in these populations. The estimated sensitivities were 18.2 and 26.6% for SIT and ELISA, respectively, whereas, specificities were 98.0 and 92.4% for SIT and ELISA, respectively. The results indicated that both tests were very insensitive but, the SIT was reasonably specific. The sero-prevalence estimates of Map varied from 7.0% in Uttar Pradesh to 77.9% in Tamil Nadu. As it is difficult to estimate the full impact of either of these tests for use in control or surveillance of this disease, there is a need to develop improved tests for field use in India.

Mycobacterium bovis detection from milk of negative skin test cows

Mycobacterium bovis is the bovine tuberculosis (bTB) agent, which is still an important infection in bovine herds. Apart from this, bTB is also a zoonotic disease, and human beings can...

Evaluation of two cocktails containing ESAT-6, CFP-10 and Rv-3615c in the intradermal test and the interferon-γ assay for diagnosis of bovine tuberculosis

The intradermal tuberculin tests and the interferon-gamma (IFN-γ) assay are the principal tests used worldwide for the ante-mortem diagnosis of bovine tuberculosis. The conventional reagent currently in use in these tests is purified protein derivative (PPD) tuberculin obtained from Mycobacterium bovis culture. The components of PPD are poorly characterized and difficult to standardize. To overcome this issue, antigens specific to the Mycobacterium tuberculosis complex are being studied. Here we have assessed the biological potency of ESAT-6, CFP-10 and Rv-3615c presented as peptide or recombinant protein cocktails in comparison with the standard bovine PPD used routinely in Spanish eradication campaigns. The study was performed in cattle (n=23) from a herd with natural M. bovis infection. Animals were simultaneously injected with PPD and the peptide and protein cocktails. The percentages of cattle reacting positively to single intradermal test were 60.9% (bovine PPD), 47.8% (peptide cocktail) and 60.9% (protein cocktail), with no significant difference between the actual skin fold thickness increases (p>0.05). The IFN-γ assay detected 60.9% of animals when stimulation was performed with bovine PPD, but decreased to 52.2% when stimulation was performed with the peptide cocktail and to 47.8% when stimulation was performed with the protein cocktail. However, no significant differences were found between IFN-γ responder frequencies (p>0.05). These results show a potential use of these defined reagents for in vivo tuberculosis diagnosis.

Comparison of tuberculin skin test with Interferon-&amp;amp;#x03B3; assay for the diagnosis of bovine tuberculosis in Korean cattle

Bovine tuberculosis (bTB), caused primarily by Mycobacterium bovis, continues to exert an economic loss, even in countries with active control measures, and is one of zoonotic diseases enable to be transmitted to human. The control and eradication of bTB are mainly based on a test and slaughter policy and/or abattoir surveillance. Various factors including limitation of diagnostic tests have been considered as major constraints to eradication. Single intradermal test (SIT) is the official diagnostic test. New diagnostic methods are needed to be developed, because of limitations of the test. In the present study SIT was compared with single intradermal comparative cervical test (SICCT) and interferon (IFN)-γ assay. There was very low correlation between SIT and SICCT. However, high correlation was shown between SIT and IFN-γ assay while no correlation was observed between SICCT and IFN-γ assay. Therefore, our results suggest the possibility of replacement of SIT with IFN-γ assay for the diagnosis of bovine tuberculosis.

The comparative performance of the single intradermal test and the single intradermal comparative tuberculin test in Irish cattle, using tuberculin PPD combinations of differing potencies

In national bovine tuberculosis (BTB) control programmes, testing is generally conducted using a single source of bovine purified protein derivative (PPD) tuberculin. Alternative tuberculin sources should be identified as part of a broad risk management strategy as problems of supply or quality cannot be discounted. This study was conducted to compare the impact of different potencies of a single bovine PPD tuberculin on the field performance of the single intradermal comparative tuberculin test (SICTT) and single intradermal test (SIT). Three trial potencies of bovine PPD tuberculin, as assayed in naturally infected bovines, namely, low (1192IU/dose), normal (6184IU/dose) and high (12,554IU/dose) were used. Three SICTTs (using) were conducted on 2102 animals. Test results were compared based on reactor-status and changes in skin-thickness at the bovine tuberculin injection site. There was a significant difference in the number of reactors detected using the high and low potency tuberculins. In the SICTT, high and low potency tuberculin detected 40% more and 50% fewer reactors, respectively, than normal potency tuberculin. Furthermore, use of the low potency tuberculin in the SICTT failed to detect 20% of 35 animals with visible lesions, and in the SIT 11% of the visible lesion animals would have been classified as negative. Tuberculin potency is critical to the performance of both the SICTT and SIT. Tuberculin of different potencies will affect reactor disclosure rates, confounding between-year or between-country comparisons. Independent checks of tuberculin potency are an important aspect of quality control in national BTB control programmes.

A fluorescence polarization assay for the detection of antibodies to Mycobacterium bovis in cattle sera

A fluorescence polarization assay (FPA) utilizing fluorescein-labelled MPB70 protein as the antigen was developed and evaluated for its ability to detect antibodies to Mycobacterium bovis in cattle sera. Three panels of sera were examined in this study. These included: (A) sera ( n=28) obtained from cattle from which M. bovis was cultured; (B) sera ( n=5666) from Canadian field cattle which were presumed to be free from M. bovis; (C) sera ( n=10) from cattle infected with Mycobacterium paratuberculosis and known to contain antibodies to this organism. Receiver operating characteristic (ROC) curve analysis of the results of panels A and B yielded an area under the curve value of 0.975 (95% confidence interval=0.971–0.979), which indicated that this FPA is an accurate indicator of M. bovis infection. At the cut-off point recommended by the ROC curve analysis, the FPA sensitivity and specificity estimates were 92.9% (95% confidence interval=76.5–98.9%) and 98.3% (95% confidence interval=97.9–98.6%) respectively. The FPA results were compared to the results of the single intradermal (SID) test for the 28 infected cattle. Fifteen of these animals were scored positive with the SID test (sensitivity=53.6%). The FPA detected 15/15 (100%) of the SID test-positive animals and 11/13 (84.6%) of the SID test-negative animals. Two of the culture-positive cattle were not detected by either test. None of the sera that were obtained from the M. paratuberculosis-infected animals cross-reacted in this assay.

An evaluation of tuberculin skin tests used to diagnose tuberculosis in swamp buffaloes ( Bubalus bubalis)

Three types of tuberculin tests were evaluated in swamp buffaloes in two herds of known tuberculosis-positive and tuberculosis-negative status, and the results were compared with post-mortem records of 73 tuberculous and 12 non-tuberculous buffaloes from a different herd. Of the 73 tuberculous swamp buffaloes, 30 (41%), 46 (63%) and 56 (77%) animals were detected by the caudal-fold skin test, the cervical skin test and the Stormont test, respectively. Of the 12 non-tuberculous buffaloes, 5 (42%), 4 (34%), and 10 (83%) reacted to the above-mentioned three tuberculin tests, respectively. The reaction was more-pronounced in the cervical skin than in the caudal-fold skin when the single intradermal test was used on the same individual. The Stormont test (a form of the double intradermal test) was the most-sensitive but least-specific test. We concluded that the tuberculin tests described showed poor sensitivity and specificity in swamp buffaloes. Another diagnostic procedure should thus be sought for more-accurate diagnosis.