Bovine Tuberculosis Eradication Program Research Articles

Private veterinarians' views of the Irish bovine TB eradication programme

There is limited understanding of Private Veterinary Practitioners' (PVPs) perceptions of, opinions about and attitudes towards the Irish Bovine Tuberculosis (bTB) eradication programme. Understanding their attitudes and behaviors towards the bTB eradication programme is both timely and crucial as their actions have a great influence on the effectiveness and sustainability of the programme itself. To date, PVPs have been consulted about how they view their role in the programme, however, less is known about the challenges they face in carrying out good quality bTB testing, and how likely they feel the programme will succeed to eradicate bTB in the future. The results from this study represent a good part of the probable sphere of perceptions, behaviors, attitudes and knowledge of the respective study population and several key critical points that are believed to have hindered the success of the bTB eradication programme in Ireland to date. This study progressed our understanding of the reasons for why farmers are demotivated by and disconnected with the Irish bTB eradication programme according to PVPs, how PVPs feel challenged in their role carrying out bTB testing, and their views on how, if possible, bTB can be eradicated in the future. Their insights will influence how the Department of Agriculture, Food and the Marine (DAFM) interacts with PVPs and farmers in the future with respect to the bTB and the eradication programme.

Improving the communication between farmers and veterinarians to enhance the acceptability of bovine tuberculosis eradication programmes.

France and Spain have been fighting against bovine tuberculosis (bTB) for years, even though new outbreaks continue to appear on both sides of the border, generating misconceptions about the disease and social distrust in the eradication programme and competent authorities. The perceived disease risk and the commitment of all interested parties are key factors for the successful implementation of control programmes, as they might influence the acceptability of recommended measures. Effective communication can contribute to increasing knowledge, trust and stakeholders' engagement, thus ensuring the acceptability of the eradication programme. This study was conducted in Catalonia (Spain) and Pyrenees-Atlantiques (France) in the frame of the INNOTUB project (https://innotub.eu/) to characterise the communication on bTB in the trans-Pyrenees region and provide recommendations to improve it. The communication on bTB was characterised by analysing 153 (Spain) and 66 (France) online freely available texts, published between 2018 and 2020, through Content Analysis and Critical Metaphor Analysis. Moreover, six farmers and four veterinarians were in-depth interviewed in each area to gather information about the communication on bTB. Interviews were made in original languages and analysed using a qualitative thematic approach. A pilot participatory intervention inspired by the Systematic Tool for Behavioural Assumption Validation and Exploration (STAVE) method was used to develop a list of proposals to improve communication and to promote the creation of territorial networks/committees on bTB prevention and control. It included three focus groups with farmers and veterinarians, a meeting with representatives of the regional veterinary services, and a final deliberative workshop. Results highlight the existence of a controversial debate on bTB and a heterogeneous understanding between stakeholders. Institutional and scientific communication mainly focus on bTB detection and control while other aspects are left in the background. On the contrary, farmers extend their communication to a greater variety of topics. The metaphorical framing strongly differed among actors, while veterinary services and researchers "fight" against bTB and "progress" toward the eradication, farmers place themselves in a framework of "sacrifice" and, particularly in Spain, they play a passive role. The proposals developed by the participants to improve the current communication on bTB included: (i) create participatory meeting spaces to share opinions and information; (ii) improve data accessibility (on epidemiological situations); (iii) develop clearer and written protocols and informative visual material; (iv) redesign the training courses (v) increase the stakeholders' participation in the design of protocols.

Tuberculosis Epidemiology and Spatial Ecology at the Cattle-Wild Boar Interface in Northern Spain

Tuberculosis (TB) is a contagious chronic disease due to infection with Mycobacterium tuberculosis complex (MTC) bacteria. Monitoring of wildlife, especially potential reservoirs, is important for detecting changes in disease occurrence and assessing the impact of interventions. Here, we examined whether wild boar (Sus scrofa) may contribute to the re-emergence of TB in Asturias (10,604 km2), northern Spain. Although this province was declared free of TB in cattle in November 2021, MTC bacteria remain prevalent in several “hotspots,” with the European badger (Meles meles) suggested as a TB potential wild reservoir. Drawing on data from the Spanish National Bovine Tuberculosis Eradication Program and the Government of the Principality of Asturias covering the period 2014–2020, we analyzed the prevalence of TB in cattle and wild boar in this region. In hotspots (592 km2), we also investigated the ranging behavior and habitat use of five cows that belonged to farms with a history of TB and six trapped sympatric wild boar. During the observation period, TB prevalence was 0.14% among cattle overall and 0.13–0.41% in hotspots, which was much lower than the prevalence in wild boar, which was 3.15% overall and 5.23–5.96% in hotspots. Infected cattle and infected wild boar in hotspots shared the same strains of M. bovis, and GPS tracking showed spatiotemporal overlap between the species, mainly around pastures during sunrise (06:00–07:00 h) and sunset (19:00–20:00 h). Our results suggest that in addition to cattle and badgers, wild boar possibly help maintain TB in northern Spain, increasing the host richness that influences TB transmission risk in the area, which should be taken into account in monitoring and eradication efforts.

Revisiting the relative effectiveness of slaughterhouses in Ireland to detect tuberculosis lesions in cattle (2014-2018).

Slaughterhouse or meat factory surveillance to detect factory lesions (FL) at slaughter is an important part of the bovine tuberculosis (bTB) eradication program in Ireland. The objective of this study was to quantify the effectiveness of Irish slaughterhouses or factories in submitting FL and the proportion of those submitted FL confirmed as being due to bTB in slaughtered cattle, and to identify and quantify the association of risk factors at animal, herd, and factory level with FL submission and confirmation. The data consisted of 6,611,854 animals slaughtered in Irish factories from 2014 to 2018 obtained from the Department of Agriculture, Food and Marine (DAFM), Ireland. Selected risk factors for this study included factory, year and month of slaughter, age, sex, breed, animal movement, ever inconclusive in the standard or severe skin test, herd type, herd size, and bTB history. The association of each risk factor on the FL submission and confirmation risk were analysed with univariable followed by a multivariable logistic regression with herd as random effect. Factories were ranked and compared based on the odds ratio (OR) obtained from the univariable (crude OR) and multivariable (adjusted OR) analysis. The average submission risk of all factories was 20 per 10,000 animals slaughtered, ranging from 1 to 42 per 10,000 animals slaughtered, and the average confirmation risk over all factories was 40.72%, ranging from 0.00 to 61.84%. The odds of submitting and confirming FL as bTB positive were higher in animals over eight years old compared to animals 1-2 years old (OR = 1.91, 95 CI 95% 1.77-2.06 and OR = 4.05, 95% CI 3.17-5.18, respectively), and were higher in animals that ever had inconclusive skin result based on severe interpretation (OR = 2.83, 95% CI 2.44-3.27 and OR = 4.48, 95% CI 2.66-7.54, respectively), animals originating from sucklers herds (OR = 1.08, 95% CI 1.02-1.14 and OR = 1.31, 95% CI 1.11-1.55, respectively), or herds with bTB history in the past three years (OR = 4.46, 95% CI 4.28-4.66 and OR = 319.90, 95% CI 237.98-430.04, respectively). The odds of FL submission and confirmation decreased as the herd size increased (OR = 0.95, 95% CI 0.93-0.96 and OR = 0.82, 95% CI 0.78-0.86, respectively). An inverse relationship of FL submission and confirmation was present for variable sex and inconclusive skin result with standard interpretation, where submission odds were higher in males (OR = 1.05, 95% CI 1.00-1.10) and ever inconclusive animals (OR = 74.24, 95% CI 69.39-79.43), although the confirmation odds were lower (males OR = 0.66, 95% CI 0.56-0.76; ever inconclusive OR = 0.44, 95% CI 0.36-0.54). The crude and adjusted ranking of factories did not differ greatly for FL submission, indicating that factory-related factors may contribute significantly to the submission variation between factories. However, a substantial difference between crude and adjusted confirmation ranking was present which may indicate that animal and herd-related factors were associated to variation in confirmation risk between factories.

Bovine tuberculosis control in Fiji: Retrospective study findings for 2015 to 2020.

Control of bovine tuberculosis (bTB) is a priority for animal health, biosecurity, and human health authorities in Fiji as evident from the long-term funding of the Bovine Brucellosis and Tuberculosis Eradication and Control program (BTEC) and notable improvements to the program described in this paper. To evaluate the performance of the Fiji BTEC program from 2015 to 2020, all available bTB data for cattle were analyzed. Data sources included BTEC bTB testing records, abattoir records and laboratory records. We integrated all information to quantify the bTB tests applied, bTB positive farms and animals, meat inspection and laboratory findings. Test coverage was highest among dairy cattle in Central Division (~73%), where bTB was highly prevalent with 7.8% of dairy cattle and 61.7% of dairy farms found to be positive between 2015 and 2020. There was no visible downward trend in the apparent prevalence of bTB over the 6-year period. During 2019 and 2020, only 21.3% (51/239) of the tested dairy farms maintained their clear status, another 8.4% (20/239) reverted to infected status after 1 year or more of being bTB clear, and most farms remained infected during these 2 years. Factors observed to be contributing to this situation were persistent infections, related in part to the significant number of untested animals, uncontrolled animal movements, and larger farm size. Similar to other developing countries, bTB remains a serious concern and further strengthening of the program targeting the main contributors to bTB persistence, along with maintenance of a comprehensive reporting and traceability system, industry awareness and government support are needed. Control of bTB in Fiji is a long-term objective that must have multiple stakeholder engagement and regular review to measure success.

Isolamento e identificação molecular de Mycobacterium bovis em lesões teciduais de bovinos abatidos em matadouros-frigoríficos localizados no estado do Ceará

ABSTRACT The objective of this research was to identify Mycobacterium bovis in lesions suggestive of tuberculosis in bovine carcasses in the State of Ceará, by means of bacteriological and molecular diagnostic tests. Between August 2017 and January 2019, the State inspection service (SIE) inspected 59,512 cattle, of which 7.4% (44 / 59,512) presented suggestive lesions. Of these animals, 68 samples were sent, of which 4.5% (31/68) located in the lung, 2.9% (20/68) in lymph nodes, 2.0% (14/68) in the liver, and 0.4% in the carcass (3/68). When performing bacteriological isolation, 15.9% (7/44) of bovines showed colony growth in the samples. The smears of the isolates were submitted to Zielh-Neelsen staining and all confirmed acid-fast bacilli. The polymerase chain reaction identified all isolates 100% (7/7) as M. bovis. The association of diagnostic techniques allowed to identify the presence of the agent in the State and the molecular analysis proved to be a beneficial technique in the monitoring of bovine tuberculosis and can be used as an auxiliary method in the bovine tuberculosis control and eradication program in the State of Ceará.

Evaluation of using comparative intradermal tuberculin test to diagnose bovine tuberculosis in dairy cattle in Taiwan.

The National Bovine Tuberculosis (bTB) Eradication Program for dairy cattle has been operating in Taiwan for many years and has allowed the prevalence of bTB to decrease gradually. However, 29% of intradermal tuberculin test (ITT)-positive dairy cows were later found to be TB negative based on necropsy, histopathological examination, and mycobacterial isolation results. Studies in Taiwan have indicated that Mycobacterium avium subsp. paratuberculosis (MAP) may lead to false-positive ITT. Due to the high prevalence (over 90%) of paratuberculosis (PTB) serum antibody among Taiwan's farms, comparative ITT (CITT) has been recommended to differentiate between bTB and PTB infections. In this study, we used ITT, CITT, and enzyme-linked immunosorbent assay (ELISA) to evaluate the prevalence of bTB from 2012 to 2018. We also used pathological and bacterial examination from ITT-positive dairy cows to evaluate CITT's diagnostic ability and adjust its cutoff point accordingly. After careful selection, 36 cows (including 31 cows from 11 ITT-positive farms and 5 from 2 ITT-negative farms) were examined by CITT. The cutoff point was adjusted using a receiver operating characteristic (ROC) analysis. Overall, our results identified the ITT-positive prevalence in Taiwan as 0.03-0.22%, and PTB-positive prevalence as 54.55-73.53%. The results of sensitivity, specificity, kappa, and ROC analyses have identified the optimal cutoff point for the CITT in Taiwan as ≥ 3mm. At this cutoff point value, the sensitivity and specificity were 62.5% and 96.43%, respectively. Our findings can be used to reduce the false-positive response rate caused by PTB cross-reaction and accelerate the eradication of bTB in Taiwan.

An abattoir-based study on the prevalence of bovine tuberculosis from culled adult dairy cows in Wuhan, China

Abattoir surveillance is an integral component of a bovine tuberculosis (bTB) eradication programme. The objective of this study was to determine the prevalence of bTB among culled adult dairy cows in Wuhan, China and to further assess two diagnostic procedures as an adjunct to the confirmation of M. bovis in animals with TB-like lesions. The study was conducted in an abattoir located in Wuhan, China over a period of 41 days from June to July 2019. A total of 171 culled adult dairy cows were sampled and inspected, and blood samples collected from 134 of these. The viscera and lymph nodes of the carcasses were visually inspected and palpated for TB-like lesions. A total of 28.1 % (48/171) of the carcasses had gross TB-like lesions. 89.6 % (43/48) of the animals with TB-like lesions were positive to a PCR procedure for bTB. The sensitivity and specificity for post-mortem examination for TB-like lesions using a Bayesian latent class analysis model was estimated to be 60.8 % and 86.6 %, respectively. A seroprevalence of 20.9 % (28/134) was recorded for antibody response to M. bovis antigens MPB70 and MPB83 based on an ELISA procedure. There was a low-moderate agreement between the ELISA and PCR results in the detection of bTB (Kappa = 0.46, 95 % CI: 0.24−0.67). The study confirms a high prevalence of bTB among culled adult dairy cows in the abattoir and highlights the need to implement surveillance for bTB based on post-mortem examination and ELISA and PCR methods in association with backward tracing of infected dairy herds.

Is moving from targeted culling to BCG-vaccination of badgers (Meles meles) associated with an unacceptable increased incidence of cattle herd tuberculosis in the Republic of Ireland? A practical non-inferiority wildlife intervention study in the Republic of Ireland (2011-2017)

Bovine tuberculosis (BTB) remains as a costly disease of cattle-herds in the Republic of Ireland (ROI). This persistence is partially attributable to the presence of M. bovis infection in a wildlife reservoir, the European badger (Meles meles). Thus, both area-wide and limited-area targeted-badger-culling have been part of the ROI-BTB control/eradication program to help reduce the future incidence of a cattle-herd BTB breakdown (i.e. a “new herd-level occurrence of BTB”). However, neither badger-culling practice can be sustained as a major component in the ongoing BTB eradication program in the ROI.Vaccination of badgers with Bacille Calmette-Guérin (BCG) has been proposed as an alternative to badger culling. Thus, in 2011, a five-year non-inferiority study was implemented in seven counties in the ROI. This study was designed to compare and contrast the cattle-herd-BTB-incidence in areas where intramuscular badger vaccination would be implemented versus the cattle-herd-BTB-incidence in the remaining area of the same county where targeted-badger-culling was maintained as the standard treatment response to probable badger-sourced BTB breakdowns.Our outcome of interest was a new cattle-herd-BTB-episode (breakdown) with a total of >2 standard skin-test (SICTT) reactors detected during the episode. Treatments (badger vaccination or targeted badger culling) were cluster allocated based on where the majority of the herd owner’s land was located. To assess the impact of the two treatments, we compared the incidence-risk, of our defined outcome, for cattle herds in the area under vaccination to the outcome incidence-risk for cattle herds in the remainder of the same county after 4 and 5 years of having implemented badger vaccination.A random-effects logit model with adjustment for clustering by treatment, and statistical control of herd-type, herd-size and five-year prior-BTB-episode history was used for our analyses. Although not included in the logistic model, a relative badger density metric based on the annual number of badgers captured-per-sett-night of capturing effort was developed for each treatment area; this metric indicated that relative badger density was approximately 40 % higher in vaccination areas than in the targeted badger-culling areas during our study.Overall, our study results indicated that vaccination was not inferior to targeted badger-culling in four counties and badger vaccination was deemed to produce ambivalent results in one (County Cork North) of the seven study sites in the ROI.A post-study investigation, in County Galway, where vaccination was deemed inferior to target culling, revealed that widespread purchases of cattle from a nearby cattle mart, by herd owners in the vaccination-area, was associated with the increased herd and vaccination-area risk of BTB. No single “biasing hypothesis” was evident for the apparent vaccine inferiority in the second study site (County Monaghan) where vaccination was deemed inferior to targeted culling; hence no further investigations were conducted.

Mongoose (Herpestes auropunctatus) May Not Be Reservoir Hosts for Mycobacterium bovis in Fiji Despite High Population Density and Direct Contact with Cattle.

The presence of a wildlife reservoir for Mycobacterium bovis complicates the eradication of bovine tuberculosis (BTB) from domestic cattle populations. For the BTB eradication program in Fiji, there is concern about the small Indian mongoose (Herpestes auropunctatus), which is overabundant and in direct contact with cattle. Consequently, a survey of mongooses trapped on three BTB affected dairy farms led to necropsy of 85 mongooses during January–February 2017. Thirty (35%) mongooses had gross pathological changes including possible granulomas detected at necropsy, and tissues from these animals were taken for histopathological examination. Granulomatous lesions were present in 53% of animals examined histopathologically but acid-fast bacilli were not observed and the majority of lesions in lung and kidney were associated with the nematodes Pulmostrongylus herpestis and Capillaria sp., respectively. Nevertheless, assuming test sensitivity of 35% for the current study, from this sample of 85 mongooses it can be concluded with 95% confidence that if present in the mongoose population susceptible to trapping, M. bovis prevalence was ≤10%. The prevalence of intercurrent lesions raised concerns about gross pathology as a screening test for M. bovis infection in mongooses in Fiji, and therefore pathogen detection methods such as bacterial culture and direct tissue PCR are recommended for future surveys. These are needed to completely rule out the mongoose as a reservoir host for M. bovis in Fiji.

Assessment of the sensitivity of the bovine tuberculosis eradication program in a high prevalence region of Spain using scenario tree modeling

In spite of the efforts invested to eradicate bovine tuberculosis (bTB) in cattle, the disease is still present in several developed countries, including Spain. Among the factors related with disease persistence in high prevalence areas, the lack of sensitivity of the screening test for detection of infected herds [single intradermal tuberculin (SIT) test] can play a major role. Here, a scenario tree model mimicking the diagnostic test scheme in place in the region of Castilla y Leon (Spain) was developed to estimate the probability of detecting bTB in an infected-non detected officially tuberculosis free (OTF) herd (herd sensitivity, HSe). In order to do so the probability of detecting at least one positive animal in the SIT test with/without post-mortem (detection of lesions and culture) confirmation in an infected herd was estimated using Monte Carlo simulation through @RISK (Palisade Co, NY, USA). Uncertainty on the accuracy of the diagnostic tests was introduced in the model using distributions based on the literature. The performance of the model was evaluated by comparing the predicted number of SIT/post-mortem positive animals in infected herds with those observed in newly detected bTB-infected herds in the region in 2011–2015. The estimated HSe of the SIT test was 76.2% (95% probability interval: 19.8–97.6). According to the model, bTB infection would be then confirmed through culture in 65.3% (95% PI: 50.0–82.3) of the herds detected through the SIT test, so that overall the proportion of infected-non detected OTF herds in which the infection could be confirmed after the initial SIT test was 49.6% (95% PI: 9.75–80.3). The predicted HSe of both SIT test and culture was directly correlated with herd size. Results from the model suggest a moderate but highly variable HSe of the current surveillance system in place for bTB detection in OTF herds located in high prevalence areas, that could be maximized by performing multiple tests within a year as indicated in the Spanish eradication program (with a median SIT HSe of 87% when two consecutive tests were considered). In addition, these results highlight the usefulness of performing subsequent SIT tests to rule out infection in SIT-positive herds even when the causative agent cannot be isolated.

Tuberculin PPD Potency Assays in Naturally Infected Tuberculous Cattle as a Quality Control Measure in the Irish Bovine Tuberculosis Eradication Programme.

The Irish Bovine Tuberculosis (bTB) eradication programme operates under national legislation and fulfills OIE and EU trade requirements. Tuberculin purified protein derivative (PPD), a preparation obtained from the heat-treated products of growth and lysis of Mycobacterium bovis or Mycobacterium avium (as appropriate), is critical to the diagnosis of tuberculosis (TB). Standardization of Tuberculin PPD potency, the relative activity in sensitized animals compared to a reference standard, is essential to underpin the reliability of certification for international trade and to ensure that disease eradication programmes are effective and efficient. A Bovine International Standard Tuberculin PPD (BIS) was established by the WHO in 1986 and is used to determine comparative potencies of Tuberculin PPDs. Ideally, Tuberculin PPD potency should be evaluated in the species in which the tuberculin will be used but due to practical difficulties in performing potency assays in cattle, for routine PPD production, they are usually assayed in guinea pigs. Low potency tuberculin PPD is less efficient and thus inferior for bTB diagnosis. Difficulties experienced in the Irish bTB eradication programme have included the supply of sub-standard potency, and thus inferior, bovine (M. bovis) Tuberculin PPD in the late 1970s. The purpose of this paper is to outline the critical role of Tuberculin PPD assays carried out on naturally infected tuberculous cattle, as required by the OIE and under EU legislation in the quality control for the Irish Bovine Eradication Programme. Such assays ensure that the Tuberculin PPD used meets the diagnostic sensitivity and specificity requirements to underpin a successful national eradication programme.

Whole Genome Sequencing of Mycobacterium bovis Isolated From Livestock in the United States, 1989-2018.

The United States official bovine tuberculosis (bTB) eradication program has utilized genotyping for Mycobacterium bovis isolates since 2000 and whole genome sequencing was implemented in 2013. The program has been highly successful, yet as bTB prevalence has reached historic lows, a small number of new bTB-affected cattle herds occur annually. Therefore, understanding the epidemiology of bTB transmission is critically important, in order to target limited resources for surveillance and achieve eradication. This evaluation described the diversity and epidemiology of M. bovis isolates identified in the USA livestock. Isolates from animals within the bTB endemic area of Michigan were excluded. Broad diversity was found among 1,248 isolates, collected from affected cattle and farmed cervids herds and fed cattle during 1989–2018. Nearly 70% of isolates from 109 herds/cases during 1999–2018 were European clonal complex 1 and 30% were European clonal complex 2. The sources of infection based on the herd investigation were known for 41% of herds/cases and 59% were not epidemiologically linked to another USA origin herd. Whole genome sequencing results were consistent with the investigation findings and previously unrecognized links between herds and cases were disclosed. For herds/cases with an unknown source of infection, WGS results suggested several possible sources, including undocumented cattle movement, imported cattle and humans. The use of WGS in new cases has reduced the time and costs associated with epidemiological investigations. Within herd SNP diversity was evaluated by examining 18 herds with 10 or more isolates sequenced. Forty percent of isolates had not diverged or accumulated any SNPs, and 86% of the isolates had accumulated 3 or fewer SNPs. The results of WGS does not support a bTB reservoir in USA cattle. The bTB eradication program appears to be highly effective as the majority of herds/cases in the USA are unique strains with limited herd to herd transmission.

Evaluation of the Performance of the IDvet IFN-Gamma Test for Diagnosis of Bovine Tuberculosis in Spain.

In Spain, the national bovine tuberculosis (bTB) eradication program is based on yearly skin testing of every ≥6 weeks old animal using the single or comparative tuberculin test and parallel use of the interferon-gamma (IFN-γ) assay as an ancillary diagnostic test in infected herds. There are several versions of the latter. Recently, a new commercial IDvet IFN-γ assay has been authorized for use in the program, but there is limited scientific evidence about its performance in different epidemiological settings. Therefore, two studies to evaluate the performance of the IDvet assay were conducted. In study 1, a concordance analysis between the new IDvet and the Bovigam IFN-γ assay in use in Spain for over 10 years was conducted. In study 2, results from the IDvet assay when applied in tandem with a single intradermal tuberculin (SIT) test were used to evaluate the concordance between both tests and to estimate their sensitivity (Se) and specificity (Sp) using a Bayesian latent-class model. Field data from cattle herds located in Madrid and Castilla y Leon (Spain) were collected. For study 1, herd selection was based on a high expected prevalence of reactors to the IFN-γ assay, while herds were selected at random to estimate Se and Sp of the new IDvet assay in study 2. Agreement between the results obtained with both kits for IFN-γ assay was poor (Kappa = 0.20), and a receiver operating characteristic (ROC) analysis indicated a low Se of the new IDvet relative to the Bovigam in a heavily bTB infected population. The Bayesian latent-class analysis estimated the Se of the IDvet assay to be 36.7% [95% probability posterior interval (PPI) 14.7–78.8%] with estimated Sp close to 100% when the cut-off recommended by the manufacturer (35) was applied. At the alternative cut-off values of 16 and 4, the estimated Se of the IDvet assay increased to 49.0% (PPI: 24.8–94.1%) and 56.0% (PPI: 30.8–96.3%), respectively, while maintaining a high specificity. The results suggest that the new IDvet assay may have lower sensitivity than the Bovigam for diagnosis of bTB in cattle herds in Spain, and that adjusting its cut-off might be considered.

Farmer and Veterinarian Attitudes towards the Bovine Tuberculosis Eradication Programme in Spain: What Is Going on in the Field?

The effectiveness of health interventions against bovine tuberculosis (bTB) is influenced by several “non-biological” factors that may hamper bTB detection and control. Although the engagement of stakeholders is a key factor for the eradication programme’s success, social factors have been often ignored in the control programmes of animal diseases, especially in developed countries. In this study, we used a qualitative approach to investigate perceptions, opinions, attitudes, and beliefs of farmers, and veterinarians who may influence the effectiveness of the Spanish bTB eradication programme. The study was carried out in two phases. First, 13 key representatives of different groups involved in the programme were interviewed through exploratory interviews to identify most relevant themes circulating in the population. Interviews focused on strong and weak points of the programme; reasons for failure to achieve eradication; benefits of being disease free; future perspectives, and proposed changes to the programme. Based on these results, a thematic guide was developed and detailed information was gained through face-to-face in-depth interviews conducted on a purposive sample of 39 farmers and veterinarians. Data were analysed following an ethnographic methodology. Main results suggested that the bTB programme is perceived as a law enforcement duty without an adequate motivation of some stakeholders and a general feeling of distrust arose. The complexity of bTB epidemiology combined with gaps in knowledge and weak communication throughout stakeholders contributed to causing disbeliefs, which in turn generated different kinds of guesses and interpretations. Low reliability in the routine skin test for bTB screening was expressed and the level of confidence on test results interpretation was linked with skills and experience of public and private veterinarians in the field. Lack of training for farmers and pressure faced by veterinarians during field activities also emerged. Few benefits of being bTB free were perceived and comparative grievances referred to wildlife and other domestic reservoirs, sector-specific legislation for bullfighting farms, and the absence of specific health legislation for game hunting farms were reported. Understanding reasons for demotivation and scepticism may help institutions to ensure stakeholders’ collaboration and increase the acceptability of control measures leading to an earlier achievement of eradication.

Farm-level risk factors associated with bovine tuberculosis in the dairy sector in Eritrea.

The aim of our study was to determine the association of selected potential risk factors with the presence of bovine tuberculosis (BTB) in dairy herds in Eritrea. A case-control study was conducted in the three major milk-producing regions of the country by stratified random sampling of 61 case and 65 control herds combined with completion of a standardized pretested questionnaire pertaining 36 relevant risk factors (variables). The variables were divided into two clusters, based on potential association with either "introduction" or "establishment" of BTB on the farms to elucidate association with incident or prevalent cases separately. Subsequent to univariable analysis of the 36 risk factors at herd level, 14 of these were offered to multivariable logistic regression models. Farms with higher numbers of cows, and those with concrete floors, were 3.6, and 7.5 times more at risk for presence of BTB, respectively, compared with their references. These findings will be useful as entry points for future informed decision-making towards BTB control and eradication programme in the country.

Efficiency of slaughterhouse surveillance for the detection of bovine tuberculosis in cattle in Northern Ireland.

Post-mortem examination continues to play an important surveillance role in the bovine tuberculosis (bTB) eradication programme in Northern Ireland. It is estimated that 18-28% of new bTB herd breakdowns are disclosed by the detection of bTB lesions in animals routinely slaughtered. The purpose of this study was to compare the performance of different slaughterhouses in Northern Ireland in detecting bTB-lesioned animals at routine slaughter (LRS) and to apply the findings to maximize the sensitivity of bTB slaughterhouse surveillance. Univariate statistical analysis on cattle slaughtered in Northern Ireland during 2011-2013 revealed that the risk of LRS disclosure varied between slaughterhouses, ranging from 0·08% to 0·54%. Furthermore, the risk of confirmation of these LRS as bTB varied between slaughterhouses, ranging from 57·9% to 72·4%. Logistic regression modelling of selected risk factors found that the risk of LRS disclosure increased with age, and was higher in purchased animals, during winter months, in animals coming from high bTB incidence areas and in animals slaughtered from herds with a bTB restriction in the last 2-3 years. Adjusting for these selected factors, the risk of LRS disclosure and bTB confirmation changed very little from the univariable analysis, suggesting that differences in disclosure risks between slaughterhouses were likely to be due to factors related to the slaughterhouses, rather than to the risk status of the animals presented. Examination of procedures within these slaughterhouses is recommended to identify ways that could increase the sensitivity of their bTB surveillance.

The effectiveness of parallel gamma-interferon testing in New Zealand’s bovine tuberculosis eradication programme

In bovine tuberculosis (bTB) eradication programmes, especially where prevalence is low, sensitivity of testing in infected herds must be maximised to reduce the possibility of recrudescence of prior infection and the risk to other herds via animal movement. The gamma-interferon (γ-IFN) assay applied in parallel with intradermal tuberculin testing has been shown to increase test sensitivity. The aim of this work was to substantiate this effect in the field.A retrospective observational study was conducted on 239 New Zealand cattle breeding and dairy herds with bTB infection between 1 July 2011 and 1 September 2015 to evaluate the outcomes of new policy introduced in 2011. The investigation defined the number and proportion of reactors (animals testing positive and slaughtered) found with lesions of bTB in intradermal caudal fold testing (CFT) and parallel γ-IFN testing, at the breakdown test or first whole herd test after breakdown, WHT(1), and at the final or projected final whole herd test, WHT(F).Parallel γ-IFN testing was used in 26.8% of the 239 herds at WHT(1), and 430 animals in 49 herds were deemed reactors. One hundred and sixty (37.2%) of these reactors from 32 herds were found to have bTB lesions, despite having been negative to caudal fold testing. These 160 infected animals accounted for 29.6% of all infection found at WHT(1).At WHT(F), parallel γ-IFN testing was conducted on 93 herds and detected a total of 122 reactors in 49 herds, in addition to those found by CFT. Twenty-one of these reactors, from 13 herds, had bTB lesions at slaughter, accounting for 67.7% of all reactors found with bTB at WHT(F). Eleven of these 13 herds would have had their movement restrictions revoked based on a negative herd CFT alone, and could potentially have caused outward transmission of bTB to other herds, as well as experiencing recrudescent breakdowns.We conclude that γ-IFN testing in infected herds, in parallel with intradermal tuberculin testing, is a valuable tool in a bTB eradication programme, as it enables higher test sensitivity at both herd and animal level. The use of the γ-IFN test over a risk cohort early in a breakdown assists in removal of early infection and some cases of anergy to intradermal tuberculin testing. Parallel γ-IFN with compulsory slaughter of reactors should be considered in breeding and dairy herds in conjunction with tuberculin testing before movement control is revoked, and will assist in achieving TB freedom on a herd level and nationally.

Risk factors for cattle presenting with a confirmed bTB lesion at slaughter, from herds with no evidence of within-herd transmission

There has been a national bovine tuberculosis (bTB) eradication programme (BTBEP) in Ireland for many years. All cattle herds are tested at least annually using the Single Intradermal Comparative Tuberculin Test (SICTT). Further, abattoir surveillance is conducted on all animals at the time of slaughter. In the Irish BTBEP, a substantial number of confirmed bTB lesions are detected in non-reactor animals, to SICTT, from Officially Tuberculosis Free (OTF) herds at slaughter. In this study we investigate risk factors for non-reactor animals from OTF herds presenting with a confirmed bTB lesion at slaughter, but with no evidence of within-herd transmission.A case-control study was conducted, with animal as the unit of interest. The case animals were all SICTT non-reactor animals slaughtered in 2012, with a confirmed bTB lesion identified during routine abattoir surveillance and with no evidence of within-herd transmission. Control animals were selected from all SICTT non-reactor animals slaughtered in 2012 from OTF herds where no bTB lesion was found. Four controls matched by age (±1 year) and location (county) were randomly selected for each case. A conditional logistic regression model was developed for univariable and multivariable analysis.The final multivariable model included: number of movements, herd type, herd-size, inconclusive reactor status at any previous test, abattoir and time spent in a herd restricted for bTB. The odds of being a case increased with the number of times an animal had moved herds. Animals from suckler herds were significantly more likely to be a case compared to those from beef herds. The odds of being a case decreased with herd-size and increased as the time spent in a restricted herd increased.There were three key conclusions from this study. Firstly, the main risk factors for animals presenting with a confirmed bTB lesion at slaughter were: previous bTB exposure history, previous inconclusive reactor result at the SICTT, the number of herd movements and herd type/size. Secondly, there was very limited evidence that these animals could have been detected any earlier. Finally, there is a need to reconsider the importance of abattoir surveillance during the latter stages of an eradication campaign. As herd prevalence declines, an increasing proportion of herd restrictions will be triggered by a single bTB-lesioned animal, with no evidence of within-herd transmission.

Future risk of bovine tuberculosis recurrence among higher risk herds in Ireland

Within the Irish national bovine tuberculosis (bTB) eradication programme, controls are tighter on higher risk herds, known as H-herds. These H-herds are defined as herds that have previously had a bTB restriction (also known as a bTB episode), with at least 2 animals positive to the single intradermal comparative tuberculin test (SICTT) or with a bTB lesion detected at slaughter. Such herds are considered at higher risk of recurrence following the end of the bTB episode. In this study, we examined if, and when, the future bTB risk of H-herds returned to a similar level comparable to herds with no history of bTB. In addition, the proportion of bTB episodes in 2012 that could be attributed to the recent introduction of an infected animal was also estimated, providing an update of earlier work. The study population consisted of all Irish herds that were not bTB restricted at the start of 2012 and with at least one whole-herd SICTT in 2012, with the herd being the unit of interest. The outcome measure was a bTB restriction, defined as any herd where at least 1 standard SICTT reactor or an animal with a bTB lesion at slaughter in 2012 was identified. A logistic regression model was used to model the probability of a herd being restricted in 2012. Herds that were previously restricted had significantly higher odds of being restricted in 2012 compared to herds that had not. Similarly, the odds of being restricted in 2012 decreased as the time since the previous restriction increased, but increased as the severity of the previous restriction increased. Odds of being restricted also increased with an increase (although not linear) in herd size, the number of animals greater than 1 year of age purchased in 2011, the county incidence rate and the proportion of cows in the herd. The recent introduction of an infected animal accounted for 7.4% (6.7–8.2) of herd restrictions. This study confirms the key role of past bTB history in determining the future risk of Irish herds, with the odds related to both the severity of and time since the previous restriction. It also illustrates the difficulty in clearly defining H-herds, noting that risk persists for extended periods following a bTB restriction, regardless of breakdown severity. There is a need for robust controls on H-herds for an extended period post de-restriction.