Single Intradermal Tuberculin Test Research Articles

Temporal analysis of the interference caused by paratuberculosis vaccination on the tuberculosis diagnostic tests in goats

Vaccination against paratuberculosis (PTB) in goats is a cost-effective control strategy, and is also effective as regards preventing the onset of clinical cases. However, it causes interference in the diagnostic tests used in the control of tuberculosis (TB). A group of 99 goats from a herd with no history of TB or PTB infection was vaccinated against PTB at seven months of age. They then underwent consecutive intradermal tests [single (SIT) and comparative (CIT) intradermal tuberculin tests), interferon-gamma release assays (IGRA) and two serological tests (p22_CE and DR-ELISA) every three months, until the interference disappeared. When using the SIT test, a variable number of positive reactors were observed at 3 months (T3; 32.3%, 95% CI 23.9–42.1), 6 months (T6; 11.5%, 95% CI 6.5–19.4), 9 months (T9; 6.4%, 95% CI 3.0–13.2) and 12 months (T12; 0%, 95% CI 0–4.0) post-vaccination. In contrast, the CIT test had a specificity (Sp) of 100% (95%, CI 96.0–100, regardless of the time post-vaccination. The IGRA also obtained high Sp values throughout the study period. No significant interference in the serological tests was recorded at T3 [p22_CE, Sp = 96% (95% CI 90.1–98.4) and DR-ELISA, Sp = 98% (95% CI 92.9–99.4)], although an increase in antibody titers was observed in the following herd testing events. In conclusion, the use of the SIT test causes the onset of false-positive reactors if applied before 12 months post-vaccination in a TB-free/PTB-vaccinated herd. Nevertheless, the CIT test and IGRA obtained high Sp values under these epidemiological circumstances. The serological tests were also highly specific in the case of PTB-vaccinated goats, although their Sp decreased significantly after several intradermal tests.

The use of serological tests in combination with the intradermal tuberculin test maximizes the detection of tuberculosis infected goats

The diagnosis of tuberculosis (TB) in goats is based mainly on the single and comparative intradermal tuberculin (SIT and CIT) tests and, exceptionally, on the interferon-gamma (IFN-γ) assay, however they are not perfect in terms of sensitivity and specificity. Nevertheless, various serological assays that provide a potential cost-effective approach for the control of TB are also available or under development, and a variety of results have been reported regarding the ability of these tests to detect infected animals, particularly in the early stages of infection. In the present study, SIT/CIT and IFN-γ tests and three different serological assays were evaluated during two consecutive herd testing events in a recently infected caprine herd (n = 447) with a high prevalence of infection in order to evaluate their performance and provide field data with which to improve the TB control programs in this species. The proportion of infected animals that tested positive among all the infected goats (T+/I+ value) in the last herd testing event ranged from 26.2% (IC95%; 19.3–34.5) to 85.7% (IC95%; 78.5–90.7) using cell-based diagnostic tests. The SIT/SCIT tests detected more infected goats than the IFN-γ test, regardless of the interpretation criteria. The T+/I+ value of serology was 83.2 (IC95%; 75.2–89), although it increased significantly (P < 0.05) when using samples collected 15 days after the intradermal test (100%, IC95%; 97–100). In general, a parallel interpretation of intradermal tests with serology maximized the detection of infected goats. These results demonstrate that serological tests are valuable diagnostic tools to maximize the detection of TB infected goats, even in recent outbreaks, accelerating the eradication process.

A cross-sectional study on prevalence of bovine tuberculosis in Indian and crossbred cattle in Gangetic delta region of West Bengal, India

Aim : The aim of this study was to investigate the incidence of bovine tuberculosis (BTB), an old chronic disease having zoonotic potential, covering four districts in Gangetic delta region of West Bengal, India, and to find the prevalence in organized as well as backyard herds and variation in relation to their age, sex, and breeds. Methods : The incidence of BTB in exotic and indigenous breeds of cattle (n=173) of various age groups was investigated employing tuberculin (single intradermal tuberculin and comparative cervical tuberculin) tests and gamma interferon assay. Further, milk samples (n=96) from milching animals and antemortem (n=519) samples (nasal swab, buccal swab, and aspirates from pre-scapular lymph nodes) were also screened employing bacteriological and molecular techniques. Results : In total, 36 (25.4%) animals from organized and one (3.2%) from backyard farming sector were found positive to BTB. Polymerase chain reaction (PCR) of milk samples based on 16S rRNA amplified the 1030 bp band in four samples indicating them belonging to genus Mycobacterium. Species-specific primers used to differentiate between Mycobacterium bovis and M. tuberculosis confirmed the presence of M. bovis. Prevalence of BTB in exotic crossbred animals (34.6%) was significantly higher (p<0.001) compared to indigenous cattle (10.5%). Further, gender-wise analysis of data with respect to BTB revealed higher positivity (p<0.05) among cows/heifers (25.8%) compared to bulls/bullocks (7.3%). Although BTBpositive cattle were detected in all the age groups, no statistical difference (p=0.779) was found among them. Conclusion : The findings indicate a higher prevalence of BTB in exotic crossbred animals in Gangetic delta and variation in breed susceptibility, thereby suggesting an urgent review of the present policy on adopting national crossbreeding program and implementation of “One Health” approach.

Antibody detection tests improve the sensitivity of tuberculosis diagnosis in cattle

We evaluated the sensitivity (Se) of the single cervical intradermal tuberculin (SIT) test, two interferon-gamma (IFN-γ) assays and three different antibody detection techniques for bovine tuberculosis (bTB) diagnosis in 131 mixed beef breed cattle. The results of the diagnostic techniques performed over the whole herd, and over the animals confirmed as infected based on the presence of lesions compatible with the disease and/or M. bovis isolation were compared to determine apparent prevalence (AP) and Se.The Se of the SIT test (severe interpretation) was 63.7% (95% CI, 54.54–72.00), while the Se of the IFN-γ assays ranged between 60.2% and 92%. The proportion of infected cattle detected by the different antibody detection techniques ranged from 65.5% to 87.6%. Three of the antibody detection techniques yielded a significant higher (p<0.05) Se than that achieved with the official diagnostic techniques. In addition, the interpretation in parallel of cellular and antibody detection techniques reached the highest Se: 98.2% (95% CI, 93.78–99.51) suggesting that the use of diagnostic techniques detecting both cellular and humoral responses could be considered as an alternative in the control of bTB outbreaks in high prevalence settings.

Factors Affecting Herd Status for Bovine Tuberculosis in Dairy Cattle in Northern Thailand.

The objective of this case-control study was to identify farm-level risk factors associated with bovine tuberculosis (bTB) in dairy cows in northern Thailand. Spatial analysis was performed to identify geographical clustering of case-farms located in Chiang Mai and Chiang Rai provinces in northern Thailand. To identify management factors affecting bTB status, a matched case-control study was conducted with 20 case-farms and 38 control-farms. Case-farms were dairy farms with at least single intradermal tuberculin test- (SIT-) reactor(s) in the farms during 2011 to 2015. Control-farms were dairy farms with no SIT-reactors in the same period and located within 5 km from case-farms. Questionnaires were administered for data collection with questions based on epidemiological plausibility and characteristics of the local livestock industry. Data were analyzed using multiple logistic regressions. A significant geographic cluster was identified only in Chiang Mai province (p < 0.05). The risk factor associated with presence of SIT-reactors in dairy herds located in this region was purchasing dairy cows from dealers (OR = 5.85, 95% CI = 1.66–20.58, and p = 0.006). From this study, it was concluded that geographic clustering was identified for dairy farms with SIT-reactors in these provinces, and the cattle movements through cattle dealers increased the risks for SIT-reactor farm status.

Sensitivity of γ-interferon test used in series after tuberculin test to detect bovine tuberculosis

FRANCE has been officially bovine tuberculosis (bTB) free since 2000, but an increase in the number of outbreaks has been observed in some areas. bTB is detected through inspections at...

Risk factors for failure to detect bovine tuberculosis in cattle from infected herds across Northern Ireland (2004–2010)

Correctly identifying animals that are truly infected with a pathogen using ante-mortem tests is the cornerstone of any disease eradication programme. Failure to identify all infected animals will impede the progress towards controlling and eradicating disease and may also have unforeseen consequences when specific prevention measures are in place to avoid animal-to-animal transmission. In the case of bovine tuberculosis (bTB), the screening ante-mortem test, the Single Comparative Intradermal Tuberculin Test (SCITT), can exhibit moderate sensitivity which can result in a “hidden burden” of infection residing within the population. Using an animal-level dataset relating to the disclosure of infected cattle with Mycobacterium bovis, the causative agent of bTB within infected herds in Northern Ireland, we investigated what factors influenced the probability of an animal being a false-negative when truly infected (using post-mortem (PM) microbiological culture confirmation results to assess infection status).We found that different risk factors affected the probability of a test-negative outcome on infected animals depending on the ante-mortem test or their combination (SICTT and/or interferon gamma (IFN-ɣ) testing). Using multivariable models, SCITT disclosure performance varied significantly by age, location (region), and production type. The IFN-ɣ tests were significantly affected by region or season, but these effects depended on the cut-off used during interpretation of the test which affected the tests characteristics. Parallel use of SCITT and IFN-ɣ tests resulted in the least number of false-negatives, and their disclosure was affected by season and age-class.Understanding the factors that lead to the non-disclosure of infected animals is essential to optimise large-scale bTB disease eradication programmes.

Single nucleotide polymorphisms in toll-like receptor genes and case-control association studies with bovine tuberculosis

Aim:Toll-like receptor 2 (TLR2) and TLR4 genes play critical roles in host recognition of Mycobacterium bovis infection and initiation of innate and adaptive immune response. The present study was aimed at exploring the association of seven single nucleotide polymorphisms (SNPs) in TLR2 and TLR4 genes with susceptibility/resistance against bovine tuberculosis (bTB) infection in cattle.Materials and Methods:A case-control resource population of 35 positive and 45 negative animals was developed after screening with single intradermal tuberculin test for bTB. Resource population was screened for SNPs in TLR2 and TLR4 genes using polymerase chain reaction-restriction fragment length polymorphism. The PROC LOGISTIC procedure of SAS 9.3 was used to find an association of allelic and genotypic frequencies with bTB.Results:In TLR2 gene, two of SNPs under study (rs55617172 and rs68268253) revealed polymorphism while in the case of TLR4 gene all four SNPs under investigation (rs8193041, rs207836014, rs8193060, and rs8193069) were found to be polymorphic in case-control population. SNP locus rs55617172 in TLR2 gene was found significantly (p<0.01) associated with susceptibility/resistance to TB in cattle.Conclusion:These findings indicate the presence of SNPs in TLR2 and TLR4 genes in our resource population. Upon validation in independent, large resource population and following biological characterization, SNP rs55617172 can be incorporated in marker panel for selection of animals with greater resistance to bTB.

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.

Preliminary Study on the Prevalence of Bovine Tuberculosis and Risk Factors among Pastoralists in Gombe State, North Eastern Nigeria

A cross-sectional study was conducted in GombeState (North- eastern, Nigeria) from March, 2011 to April 2013 to estimate the prevalence of bovine tuberculosis (BTB) based on single caudal intradermal tuberculin test (SCITT), questionnaire and an abattoirs survey. The study was conducted among 250 households (100 household with a history or confirmed case of pulmonary tuberculosis and 150 households who had no history or confirmed case of pulmonary Tb), who raised 217 herds comprising of 2,245 herds of cattle. Questionnaire administration and Bioline® analysis of sputa collected from all pastoralists who were suspected to have TB and were smear positive were also conducted. Herd prevalence of SCITT was 13.87% and was higher than in herds of the negative households. At least one human Tb case was observed among 25% of the households interviewed, whereas 48% had reactor cattle. However, there was no statistically significant association (P>0.05) between the human Tb cases observed and the presence of reactor cattle. Similarly, fourty (40) isolates of Mycobacteria spp were obtained from the cultured sputa collected from the pastoralists, and were subjected to Ziehl-Nelson (ZN) and Bioline® analysis, where sixteen (16) of the (40%) were found to be M. tuberculosis complex (MTC) and the remaining 24 (60%) were members of Non- tuberculous Mycobacteria (NTM). All the isolates obtained (both sputum and tissues) which were identified as MBTC, were subjected to genotype MBTC ® Hain assay PCR analysis in order to differentiate them in to their various species of the MBTC isolates from the tissues, 8 (4.0%) were found to be M. bovis, 5(2.5%) wereM.tb and the remaining 5(2.5%) were unidentified using the standard banding patterns. The 40MBTC from sputum were analyzed as follows, 30 (75%) as M.tb, 6(15%) were M. bovis and 3(7.5%) were M. africanum. The remaining 1(0.4%) were unidentified using the standard banding patterns. All the isolates obtained (both sputum and tissues) which were identified as MBTC, were subjected to genotype MBTC ® Hain assay PCR analysis in order to differentiate them in to their various species of the MBTC isolates from the tissues, 8 (4.0%) were found to be M. bovis, 5(2.5%) wereM. tb and the remaining 5(2.5%) were unidentified using the standard banding patterns. The 40MBTC from sputum were analyzed as follows, 30 (75%) as M.tb, 6(15%) were M. bovis and 3(7.5%) were M. africanum. The remaining 1(0.4%) were unidentified using the standard banding patterns. However, a significant difference (p>0.05) was observed among the cattle age group, cattle over five (5) years were seen to have higher odds for tuberculin reactivity compared to those below the age of five (5). Out of the total cattle population (57,943) subjected to post mortem examination at the abattoir, 205 were found to be positive for gross Tb lesions, where a large proportion (50%) of the lesions were recorded in the respiratory pathway, digestive system (21%) and prescapular lymph nodes (18.6%). In spite of all these findings, it was observed that 70% (175 out of 250) of the respondents had knowledge of the existence of the disease but did not know the zoonotic implication. Also, all the potential risk factors of the disease transmission between cattle and human (milk consumption, livestock husbandry and presence of Tb positive cattle) were not statistically significantly (P< 0.05). In conclusion, it was observed that cattle belonging to the pastoralists who were positive for Mycobacterium species were more affected than those who were negative and lack of zoonotic awareness of the households. Therefore, further study to differentiate the MTC (Mycobacterium tuberculosis complex) using molecular analysis, collaboration between physicians and veterinarians and creation of awareness about the zoonotic nature of the disease were recommended.

Prevalence of Avian Tuberculosis in Domestic Chickens in Selected Sites of Ethiopia

This study was conducted on 282 domestic chickens of Bahir Dar, Yilimana densa woreda, and Bishoftu by using avian tuberculosis diagnosis procedures such as single intradermal avian tuberculin test, post mortem examination, and Ziehl-Neelsen (Z-N) staining from tissue samples of naturally infected Domestic chickens (Gallus domesticus). The overall of this disease current prevalence was determined based on tuberculin skin test results supported by Z-N stain and post mortem lesions and it was 4.26% (12/282) (95% CI: 1.9-6.6), with higher prevalence in semi-intensively reared exotic chickens (5.85%) than backyard reared indigenous local chicken. This indicates the occurrence of this disease has a statistical significance association both with the breed and production system, both having a p-value of 0.03. Twelve strong positive reactor chickens have shown a swelling of greater than 5 mm in diameter 48 h. of post injection with different variety results, some with edematous swelling, and others with firm erythematic nodular swelling. Typical tuberculous lesions were seen mostly on the liver and spleen. From 12 tuberculi reactor slaughtered chickens, a total of seven (58.3%) chickens had gross lesions on different visceral organs, of which three (42.9%) examined chickens have manifested gross lesions on more than one organ. On acid fast staining five (41.67%) with grossly discernible lesions revealed acid-fast rods. For culturing, Lowenstein-Jensen (L-J) media was used as it yields more positive cultures, greater numbers of colonies on positive tubes, and shorter incubation times. None of the samples shown colonial growth till 8 weeks of incubation period and this may be due to the slow growth nature of mycobacterial species (especially when the infection was due to Mycobacterium avium subspecies paratuberculosis which needs a considerable long time for growth) and/or the current incubation temperature (37°C) may not be optimal as it does not fit the natural hosts internal body temperature and still the culture result is under process to see any growing colony. Therefore, this finding signaling an urgent need for intervention program to control the disease in domestic chickens and prevent zoonotic transmission.

Association of polymorphisms in SLC11A1 gene with bovine tuberculosis trait among Indian cattle

ABSTRACTIn the present study, polymorphisms at two single nucleotide polymorphisms (SNPs) and one microsatellite locus of SLC11A1 gene were investigated for finding their association with susceptibility to bovine tuberculosis trait (tuberculin reaction) in Indian cattle. A total of 245 animals were tested with single intradermal tuberculin test for screening positive animals for tuberculin reaction. At rs109915208 locus very low polymorphism information content of 0.0454 was observed, whereas it was moderate (0.352) at rs109453173 locus of SLC11A1. At rs109915208 locus the genotypic as well as allelic frequencies were differing significantly (p-value < .05) in case–control animals where the odds ratio (OR) of ‘CC’ verses ‘CT’ genotype and the OR of ‘C’ verses ‘T’ allele were approaching towards infinity, suggesting that animals having ‘CT’ genotype and ‘T’ allele were less susceptible for tuberculin reaction as compared to their contemporary genotype/allele. The significantly associated SNP was non-synonymous causing an amino acid change.

Pathology and diagnosis of Mycobacterium bovis in naturally infected dromedary camels (Camelus dromedarius) in India.

The present study investigated the pathological features of tuberculosis (TB) caused by Mycobacterium bovis and its diagnosis in naturally infected dromedary camels from an organized farm in India. During the period of the 5-year study, a total of 18 (19.56%) camels out of 92 examined showed gross lesions compatible with TB at post-mortem. The clinical signs and pathological lesions in these camels were studied, and the efficacy of different diagnostic tests was also assessed. On the basis of occurrence and distribution of gross TB lesions, the infected camels revealed two different lesional patterns as pulmonary (n = 15) and disseminated (n = 3) form. The histopathology of affected organs revealed typical granulomatous lesions wherein the giant cells and acid-fast bacilli were occasionally observed in pulmonary form whereas they frequently observed in disseminated form. The single intradermal tuberculin test (SIDT) detected TB in 10 (55.55%) whereas the Ziehl-Neelsen (ZN) stain and IS6110 PCR from tissue lesions detected 13 (72.22%) and 18 (100%) of the infected camels, respectively. The study suggests that pulmonary form of the TB is more common in camels indicating respiratory route as the major source of exposure in camel herds. Moreover, very low sensitivity of SIDT was observed which highlights the difficulty for confirmation of TB in live camels.

Lack of interference with diagnostic testing for tuberculosis in goats experimentally exposed to Corynebacterium pseudotuberculosis

It has been suggested that infection with Corynebacterium pseudotuberculosis, the pathogen responsible for caseous lymphadenitis (CLA), might interfere with diagnostic testing for tuberculosis (TB), due to antigenic similarities between this particular type of bacterium and those expressed by mycobacteria. The aim of the present study was to investigate whether experimental infection with C. pseudotuberculosis in goats impacted on TB testing, using single and comparative intradermal tuberculin (SIT and SCIT respectively) tests and interferon (IFN)-γ assay. No positive reactors were detected among the CLA-affected goats using the SIT/SCIT tests or the interferon IFN-γ assay. A proportion of goats showed inconclusive results to the SIT test and reactions to Mycobacterium avium. There was no evidence that infection with C. pseudotuberculosis interferes with diagnostic testing for TB using standard interpretation of the SIT, SCIT and IFN-γ tests.

Sheep as a Potential Source of Bovine TB: Epidemiology, Pathology and Evaluation of Diagnostic Techniques.

Bovine tuberculosis (TB) infection is infrequently diagnosed in sheep. Most reports are from single individual cases or flock outbreaks. However, in Spain several outbreaks have been reported recently, all of which had epidemiological links with TB-infected cattle herds. A total of 897 sheep suspected of being infected with TB and belonging to 23 flocks cohabiting with TB-infected cattle herds and/or goats were tested between 2009 and 2013 in Galicia (north-western Spain), using pathological, immunological and molecular techniques. Of these, 50.44% were positive by culture, 83.23% by histopathology and 24.92%, 4.86% and 59.42% by single intradermal tuberculin test (SITT), interferon-γ and ELISA, respectively. Results suggest that in circumstances akin to those in our study, sheep may be considered as a potential source of TB. We conclude that under similar conditions, serious consideration should be given to TB testing sheep, as they may represent a potential risk to other susceptible co-habiting species. The SITT and ELISA are recommended as the simplest and most cost-effective initial approaches for the diagnosis of TB in sheep under field conditions. However, when possible, interferon-γ should be applied to increase sensitivity.

Evaluation of the single cervical skin test and interferon gamma responses to detect Mycobacterium bovis infected cattle in a herd co-infected with Mycobacterium avium subsp. paratuberculosis

This study reports the performance of the single intradermal tuberculin (SIT) test and the interferon-gamma (IFN-γ) assay for Mycobacterium bovis in a cattle herd with high prevalence of paratuberculosis (PTB). A total of 58/350 animals were selected for necropsy based on one or more of the following criteria: positive to SIT, IFN-γ, a breeding cow that seroconverted to PTB and showed signs compatible with a wasting disease. Infection status was determined by post mortem diagnostic tests that included histopathology examination, mycobacterial cultures and PCR identification for M. bovis and Mycobacterium avium subsp. paratuberculosis (MAP). In 7/58 animals primary tuberculosis (TB) lesions, affecting only the retropharyngeal and/or mediastinal lymph nodes, were found; 3/7 animals were found SIT positive. PTB was confirmed in 35/58 animals, of which 30 had seroconverted and 14 had typical clinical signs. 45/58 animals were IFN-γ+ using the most stringent criterion (cut-off point≥0.05); however, IFN-γ test was only positive in 33 animals when using a higher threshold (cut-off point≥0.1). Three animals co-infected also showed extensive TB and diffuse PTB lesions. These results show that the combined use of SIT and IFN-γ, as interpreted using official guidelines, detected all confirmed cases of TB. Individually, the sensitivity of the SIT was inadequate to diagnose TB-positive animals with an advanced stage of PTB. The large number of IFN-γ+ animals with no visible TB lesion could be due, in part, to some protection conferred by prior infection with MAP.

Prevalence of Bovine Tuberculosis and Risk Factor Assessment in Cattle in Rural Livestock Areas of Govuro District in the Southeast of Mozambique

BackgroundBovine tuberculosis (bTB), caused by Mycobacterium bovis, is an infectious disease of cattle that also affects other domestic animals, free-ranging and farmed wildlife, and also humans. In Mozambique, scattered surveys have reported a wide variation of bTB prevalence rates in cattle from different regions. Due to direct economic repercussions on livestock and indirect consequences for human health and wildlife, knowing the prevalence rates of the disease is essential to define an effective control strategy.Methodology/Principal findingsA cross-sectional study was conducted in Govuro district to determine bTB prevalence in cattle and identify associated risk factors. A representative sample of the cattle population was defined, stratified by livestock areas (n = 14). A total of 1136 cattle from 289 farmers were tested using the single comparative intradermal tuberculin test. The overall apparent prevalence was estimated at 39.6% (95% CI 36.8–42.5) using a diagnostic threshold cut-off according to the World Organization for Animal Health. bTB reactors were found in 13 livestock areas, with prevalence rates ranging from 8.1 to 65.8%. Age was the main risk factor; animals older than 4 years were more likely to be positive reactors (OR = 3.2, 95% CI: 2.2–4.7). Landim local breed showed a lower prevalence than crossbred animals (Landim × Brahman) (OR = 0.6, 95% CI: 0.4–0.8).Conclusions/SignificanceThe findings reveal an urgent need for intervention with effective, area-based, control measures in order to reduce bTB prevalence and prevent its spread to the human population. In addition to the high prevalence, population habits in Govuro, particularly the consumption of raw milk, clearly may potentiate the transmission to humans. Thus, further studies on human tuberculosis and the molecular characterization of the predominant strain lineages that cause bTB in cattle and humans are urgently required to evaluate the impact on human health in the region.

Assessment of the sensitivity of the gamma-interferon test and the single intradermal comparative cervical test for the diagnosis of bovine tuberculosis under field conditions

In some French départements, the eradication of bovine tuberculosis is incomplete and usual skin tests [single intradermal tuberculin test (SIT) and single intradermal comparative cervical test (SICCT)] have poor specificity due to cross-reactions with non-pathogenic mycobacteria, causing economic losses. In Côte d'Or (Burgundy, France), an experimental serial testing scheme based on the combination of SICCT and gamma-interferon (IFN-γ) tests has been initiated in order to shorten the interval between suspicion and its invalidation in herds with false-positive results to skin tests. Our aim was to assess the scheme's sensitivity and to compare it to the sensitivity of the screening scheme recommended by the European Commission. Our study included 1768 animals from Côte d'Or. The sensitivities of both schemes were estimated using a Bayesian approach. The individual sensitivity of the IFN-γ test [88·1%, 95% credibility interval (CrI) 72·8-97·5] was not significantly different from individual SICCT sensitivity (80·3%, 95% CrI 61·6-98·0) and individual SIT sensitivity (84·2%, 95% CrI 59·0-98·2). The individual specificity of the IFN-γ test was 62·3% (95% CrI 60·2-64·5). No significant difference could be demonstrated between the sensitivities of the serial testing scheme used in Côte d'Or (73·1%, 95% CrI 41·1-100) and the European Union serial testing scheme (70·1%, 95% CrI 31·5-100·0).

Risk factors associated with negative in-vivodiagnostic results in bovine tuberculosis-infected cattle in Spain

BackgroundDespite great effort and investment incurred over decades to control bovine tuberculosis (bTB), it is still one of the most important zoonotic diseases in many areas of the world. Test-and-slaughter strategies, the basis of most bTB eradication programs carried out worldwide, have demonstrated its usefulness in the control of the disease. However, in certain countries, eradication has not been achieved due in part to limitations of currently available diagnostic tests. In this study, results of in-vivo and post-mortem diagnostic tests performed on 3,614 animals from 152 bTB-infected cattle herds (beef, dairy, and bullfighting) detected in 2007–2010 in the region of Castilla y León, Spain, were analyzed to identify factors associated with positive bacteriological results in cattle that were non-reactors to the single intradermal tuberculin test, to the interferon-gamma (IFN-γ) assay, or to both tests applied in parallel (Test negative/Culture + animals, T-/C+). The association of individual factors (age, productive type, and number of herd-tests performed since the disclosure of the outbreak) with the bacteriology outcome (positive/negative) was analyzed using a mixed multivariate logistic regression model.ResultsThe proportion of non-reactors with a positive post-mortem result ranged from 24.3% in the case of the SIT test to 12.9% (IFN-γ with 0.05 threshold) and 11.9% (95% CI 9.9-11.4%) using both tests in parallel. Older (>4.5 years) and bullfighting cattle were associated with increased odds of confirmed bTB infection by bacteriology, whereas dairy cattle showed a significantly lower risk. Ancillary use of IFN-γ assay reduced the proportion of T-/C + animals in high risk groups.ConclusionsThese results demonstrate the likelihood of positive bacteriological results in non-reactor cattle is influenced by individual epidemiological factors of tested animals. Increased surveillance on non-reactors with an increased probability of being false negative could be helpful to avoid bTB persistence, particularly in chronically infected herds. These findings may aid in the development of effective strategies for eradication of bTB in Spain.

Polymerase chain reaction based detection ofMycobacterium tuberculosisIS6110 in cattle faeces

PCR amplification of insertion element IS6110 of Mycobacterium tuberculosis in fecal samples was evaluated in the diagnosis of intestinal tuberculosis (ITB). Single intradermal tuberculin test was carried in 125 cattle from organized dairy farms, off which, 36 animals gave a positive reaction. Blood and faecal samples were collected from all the tuberculin positive (36) animals. Demonstration of acid fast bacilli was done in the faecal samples by using the Ziehl - Neelsen staining. DNA was extracted and PCR was carried out in the blood and faecal samples by using IS6110 insertion sequence. Acid fast bacilli were observed in 10 (27.77%) faecal smears whereas, 18 (50%) faecal samples and 4 (11.11%) blood samples were found positive for the insertion sequence IS6110 of Mycobacterium tuberculosis complex. This result shows that IS6110 insertion sequence-PCR assay may be applied to detect tuberculous bacilli directly from faecal sample of dairy cows and therefore could be a valuable diagnostic or screening test for herds.