New assessment of bovine tuberculosis risk factors in Belgium based on nationwide molecular epidemiology

Quantitative decision making in animal health surveillance: Bovine Tuberculosis Surveillance in Belgium as case study

Despite eradication and control measures applied across Europe, bovine tuberculosis (bTB) remains a constant threat. In Belgium, after several years of official bTB-free status, routine movement testing, as currently practiced, revealed itself inadequate to detect some herds affected by sporadic breakdowns. The aim of this study was to assess different surveillance system components that strike a balance between cost and effectiveness and to identify sustainable alternatives, which substantiate a bTB-free claim while ensuring early detection and acceptance by various animal health stakeholders. For this pupose, a stochastic iteration model was used to simulate the current surveillance system's expected performance in terms of detection sensitivity and specificity. These results were then descriptively compared with observed field results. Second, the cost and effectiveness of simulated alternative surveillance components were quantified. Sensitivity analyses were performed to measure key assumptions' impacts (i.e. regarding diagnostic tests and true prevalence). The results confirmed discrepancies between the observed and simulated expected performance of bTB surveillance in Belgium. Second, simulated alternatives showed that interferon gamma (IFN-γ) and serological testing with antibody-enzyme linked immunosorbent assay (Ab-ELISA) targeting at-risk herds would enable an increase in the overall cost effectiveness (sensitivity and specificity) of the Belgian bTB surveillance system. Sensitivity analyses showed that results remained constant despite the modification of some key assumptions. While the performance of the ongoing bTB surveillance system in Belgium was questionable at the time of the study, this exercise highlighted that not only sensitivity but specificity also are key drivers of surveillance performance. The quantitative approach, taking into consideration various stakeholders' needs and priorities, revealed itself to be a useful tool in allowing evidence-based decision making for future tuberculosis surveillance in Belgium, in line with the international standards.

Relative Contribution of Each Component of the French Ante-Mortem Surveillance System for Bovine Tuberculosis in Its Overall Sensitivity

The aim of this study was to assess the contribution to the sensitivity of the French ante-mortem surveillance system for bovine tuberculosis in cattle of each of the system’s components (periodic screening, epidemiological investigations, and screening exchanged animals), on a local scale defined by administrative areas. These components were individually assessed in previous studies by scenario tree modeling. We used scenario tree modeling at the herd level and combined the results to evaluate the overall sensitivity of the ante-mortem surveillance system. The probability to detect at least one infected herd was consistent with the location of the outbreaks detected in 2016. In areas with a high apparent incidence, the probability of an infected herd to be detected was satisfactory (for an infected herd there was a 100% probability to be detected over a two-year period). Periodic screening was the most important component for the overall sensitivity in infected areas. In other areas, where periodic screening had stopped, tracing-on epidemiological investigation was the most sensitive component of the system. Screening exchanged animals had a negligible part in the overall sensitivity of the surveillance system.

Assessment of the cost-effectiveness of alternative bovine tuberculosis surveillance protocols in French cattle farms using the mixed interferon gamma test

Periodic screening in farms, using intradermal cervical comparative tuberculin test (ICCT), is a component of the French ante mortem surveillance of bovine tuberculosis (bTB). Previous studies have estimated the cost-effectiveness of the French mandatory bTB screening protocols. In these protocols, a second ICCT (ICCT2) is performed 42 days after the first one (ICCT1), either on the entire herd (strict protocol) or in series on animals with non-negative results (reactors) to ICCT1 (compliant protocol). The 42-days interval reduced protocols' cost-effectiveness. To minimize this interval, we suggested two alternative protocols, in which a mixed interferon gamma test (IFNMIX), with better sensitivity than ICCT2 and comparable specificity, replaces the ICCT2, and is carried out directly after the ICCT1. In the strict alternative protocol, reactors to ICCT1 are culled to perform laboratory analyses (PCR, bacteriology). Negative results to these analyses imply the IFNMIX testing of the entire herd. In the compliant alternative protocol, only reactor(s) to ICCT1 are tested with IFNMIX, and animals with positive results to IFNMIX are culled for laboratory analyses. We evaluated these protocols through scenario tree modelling. The estimated cost-effectiveness indexes showed that the compliant alternative protocol was the most efficient. The strict protocols (mandatory and alternative) were never the most efficient, but were the most effective. Therefore, using IFNMIX instead of ICCT2 may be useful in reducing the costs of the compliant protocol used when the probability of infection is considered low. The strict alternative protocol may become more attractive would IFNMIX's price decreased.

High discrimination of Mycobacterium bovis isolates in Brazilian herds by spoligotyping

Bovine tuberculosis is an infectious disease caused by Mycobacterium bovis (M. bovis), that leads to economic losses in infected herds and it is also considered an important zoonosis. The molecular typing methods of M. bovis isolates are fundamental for the bovine tuberculosis surveillance system, and spoligotyping is the standard genotyping technique for this species. Thus, the aim of the present study is to analyze the spatial and cluster distribution of M. bovis strains from several regions of Brazil through molecular typing. Spoligotyping technique was applied on 422 isolates identified as M. bovis, and Ripley's K function was used to perform the spatial and cluster analysis of each identified profile. Forty-three (43) different profiles were identified and spoligotype SB0121 was the most frequent and showed a uniform pattern in the spatial distribution while spoligotypes SB0295, SB1380 and SB1050 formed clusters. In addition, three novel spoligotype profiles (SB2361, SB2362, SB2364) were identified in different herds. In this perspective, it is believed that molecular identification and typing can significantly improve the performance of surveillance systems for bovine tuberculosis in Brazil.

Prevalence of Bovine Tuberculosis in India: A systematic review and meta-analysis

Bovine tuberculosis (bTB) is a chronic disease of cattle that impacts productivity and represents a major public health threat. Despite the considerable economic costs and zoonotic risk consequences associated with the disease, accurate estimates of bTB prevalence are lacking in many countries, including India, where national control programmes are not yet implemented and the disease is considered endemic. To address this critical knowledge gap, we performed a systematic review of the literature and a meta-analysis to estimate bTB prevalence in cattle in India and provide a foundation for the future formulation of rational disease control strategies and the accurate assessment of economic and health impact risks. The literature search was performed in accordance with PRISMA guidelines and identified 285 cross-sectional studies on bTB in cattle in India across four electronic databases and handpicked publications. Of these, 44 articles were included, contributing a total of 82,419 cows and buffaloes across 18 states and one union territory in India. Based on a random-effects (RE) meta-regression model, the analysis revealed a pooled prevalence estimate of 7.3% (95% CI: 5.6, 9.5), indicating that there may be an estimated 21.8 million (95% CI: 16.6, 28.4) infected cattle in India-a population greater than the total number of dairy cows in the United States. The analyses further suggest that production system, species, breed, study location, diagnostic technique, sample size and study period are likely moderators of bTB prevalence in India and need to be considered when developing future disease surveillance and control programmes. Taken together with the projected increase in intensification of dairy production and the subsequent increase in the likelihood of zoonotic transmission, the results of our study suggest that attempts to eliminate tuberculosis from humans will require simultaneous consideration of bTB control in cattle population in countries such as India.

Epidemiology of Mycobacterium bovis and Mycobacterium tuberculosis in animals: Transmission dynamics and control challenges of zoonotic TB in Ethiopia

Mycobacterium tuberculosis complex is the cause of tuberculosis (TB) in humans and other animals. Specifically, Mycobacterium bovis (M. bovis) and Mycobacterium tuberculosis (M. tuberculosis) are highly pathogenic mycobacteria that may infect different animal species and are the sources of TB in humans. The objective of this paper was to review the epidemiology of M. bovis and M. tuberculosis in animals. The review also highlighted the transmission dynamics of M. bovis and M. tuberculosis in humans and animals and control challenges of zoonotic TB in Ethiopia. The literature review focused on scientific peer-reviewed articles from studies exclusively conducted in Ethiopia that were published from 1998 to 2017. Husbandry system, breed and herd size have significant role in the epidemiology of bovine tuberculosis (BTB) in Ethiopia. The information presented reveals that different strains of M. bovis are widely distributed in domestic animals predominantly in the Ethiopian cattle and the main strain was found to be SB1176. In addition, the isolation of M. tuberculosis from domestic animals in different settings signifies the circulation of the agent between humans and animals in Ethiopia. The life styles of the Ethiopian communities, close contact with domestic animals and/or the habit of consuming raw animal products, are suggested as the main factors for transmission of M. bovis and M. tuberculosis between human and animal which may have impact on the TB control program in human. In Ethiopia, a human TB control program has been widely implemented, however, the role of animal in the transmission of the causative agent has been neglected which could be one of the challenges for an effective control program. This warrants the need for incorporating animal TB control programs using "One Health" approach for effective TB control for both human and animal.

Bovine Tuberculosis in Britain and Ireland - A Perfect Storm? the Confluence of Potential Ecological and Epidemiological Impediments to Controlling a Chronic Infectious Disease

Successful eradication schemes for bovine tuberculosis (bTB) have been implemented in a number of European and other countries over the last 50 years. However, the islands of Britain and Ireland remain a significant aberration to this trend, with the recent exception of Scotland. Why have eradication schemes failed within these countries, while apparently similar programs have been successful elsewhere? While significant socio-economic and political factors have been discussed elsewhere as key determinants of disease eradication, here we review some of the potential ecological and epidemiological constraints that are present in these islands relative to other parts of Europe. We argue that the convergence of these potential factors may interact additively to diminish the potential of the present control programs to achieve eradication. Issues identified include heterogeneity of diagnostic testing approaches, the presence of an abundant wildlife reservoir of infection and the challenge of sustainably managing this risk effectively; the nature, size, density and network structure of cattle farming; potential effects of Mycobacterium bovis strain heterogeneity on disease transmission dynamics; possible impacts of concurrent endemic infections on the disclosure of truly infected animals; climatological differences and change coupled with environmental contamination. We further argue that control and eradication of this complex disease may benefit from an ecosystem level approach to management. We hope that this perspective can stimulate a new conversation about the many factors potentially impacting bTB eradication schemes in Britain and Ireland and possibly stimulate new research in the areas identified.

Prevalence and risk factors of mycobacterial infections in farm and trade cattle in southwestern Nigeria

We evaluated the prevalence of mycobacterial infections (i.e., Mycobacterium bovis and non-tuberculous mycobacteria [NTM]) and their associated risk factors among cattle herds and trade cattle in southwestern Nigeria. Through cross-sectional study design, cattle herds from three locations were screened using the single intradermal comparative cervical tuberculin test based on two diagnostic standards; more than 4 mm (˃ 4 mm) and more than 2 mm (˃ 2 mm) cut-off points. Abattoir study involved screening trade cattle for tuberculous lesions. Overall, 515 cattle from 45 herds were screened. Using > 4 mm, animal level and herd prevalence of 11.7 and 46.7% were recorded, respectively. Applying the ˃ 2 mm cut-off, animal level and herd prevalence increased to 31.1 and 60.0%, respectively. Significantly, using the ˃ 2 mm cut-off, cattle in medium size herds/extensive management system (OR = 1.6; 95% CI 1.1-2.5) and Sokoto Gudali (OR = 2.3; 95% CI 1.4-3.8) were more at risk of being positive reactors, while Rahaji (OR = 0.3; 95% CI 0.1-0.7) breeds of cattle and cows in the peri-urban area (OR = 0.4; 95% CI 0.2-0.9) were less at risk of being positive reactors. Again, M. avium reactor of 21.7% was observed. In the abattoir, 1797 cattle were examined with 126 lesions suggestive of tuberculosis (TB). Culture/molecular analyses confirmed 2.2% M. bovis and 0.9% NTM infections. Risk factors associated with bovine TB among trade cattle were sex (OR = 4.0; 95% CI 1.2-13.5) and age (OR = 0.3; 95% CI 0.1-0.9). We confirm 11.7% prevalence of mycobacterial infections among populations of cattle screened with breed and herd size being major risk factors.

Molecular epidemiology of Mycobacterium tuberculosis complex strains isolated from livestock and wild animals in Italy suggests the need for a different eradication strategy for bovine tuberculosis

Bovine tuberculosis (bTB) is an important zoonosis, which has been re-emerging in different ecological scenarios. In Sicily, Italy, from 2004 to 2014, an anatomopathological survey for tuberculosis-like lesions both in farmed and wild animals was performed. The isolates were genotyped using spoligotyping and Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) techniques. High prevalence of lesions was observed for cattle (4%), pigs (4.9%) and wild boars (6.8%), and a total of 625 Mycobacterium bovis isolates were identified. Genotyping analysis showed the presence of 37 different spoligotypes including fifteen spoligotypes not present in other Italian regions and 266 MIRU-VNTR profiles. Spoligotype SB0120 exhibited the highest prevalence in cattle (50%) and pigs (56%) and the highest genetic variety with 126 different MIRU-VNTR profiles. The isolation of M. bovis in a farmer underlines the importance of M. bovis identification during the human TB diagnostic processes. This study supported the use of the genotyping analysis as a valuable tool for the evaluation of the epidemiological role of pigs and other domestic reservoirs such as goats and the role of wildlife in the maintenance of bTB infection.

Whole genome sequencing of Mycobacterium bovis to obtain molecular fingerprints in human and cattle isolates from Baja California, Mexico

OBJECTIVES

To determine genetic diversity by comparing the whole genome sequences of cattle and human Mycobacterium bovis isolates from Baja California.

METHODS

A whole genome sequencing strategy was used to obtain the molecular fingerprints of 172 isolates of M. bovis obtained from Baja California, Mexico; 155 isolates were from cattle and 17 isolates were from humans. Spoligotypes were characterized in silico and single nucleotide polymorphism (SNP) differences between the isolates were evaluated.

RESULTS

A total of 12 M. bovis spoligotype patterns were identified in cattle and humans. Two predominant spoligotypes patterns were seen in both cattle and humans: SB0145 and SB1040. The SB0145 spoligotype represented 59% of cattle isolates (n=91) and 65% of human isolates (n=11), while the SB1040 spoligotype represented 30% of cattle isolates (n=47) and 30% of human isolates (n=5). When evaluating SNP differences, the human isolates were intimately intertwined with the cattle isolates.

CONCLUSIONS

All isolates from humans had spoligotype patterns that matched those observed in the cattle isolates, and all human isolates shared common ancestors with cattle in Baja California based on SNP analysis. This suggests that most human tuberculosis caused by M. bovis in Baja California is derived from M. bovis circulating in Baja California cattle. These results reinforce the importance of bovine tuberculosis surveillance and control in this region.

THE PREVALENCE OF TUBERCULOSIS IN CATTLE AND THEIR HANDLERS IN NORTH TONGU, VOLTA REGION, GHANA

BACKGROUND

The need to understand the contribution of bovine tuberculosis (BTB) to the general tuberculosis burden in a poor resource setting is paramount. The aim of this study is to determine the burden of BTB among herdsmen and cattle in the North Tongu district of Volta Region in Ghana.

MATERIALS AND METHODS

A cross- sectional study was conducted in the North Tongu District of the Volta Region between the period of October 2011- March 2012. A well-structured questionnaire was used to collect socio-demographic information and possible risk factor information on cattle from participants. Sputum samples from 68 herdsmen and blood samples from 200 cattle belonging to these herdsmen were also collected. Sputum samples were analyzed using Ziehl- Neelsen staining while Anigen Rapid BTB Test was used for Cattle blood samples.

RESULTS

Ninety percent (61/68) of respondents were also found to consume fresh milk while 84% (57/68) do not use protective clothing. Of a total of 1580 cattle owned by the herdsmen, 200 cattle consisting of 14 bulls and 186 cows were screened where the prevalence of bovine TB was 19% (38/200) and those affected were all females. All (100%) human sample tested negative for Acid-Fast Bacilli (AFB). However, the seropositivity of cattle and kraal density were statistically associated (p= 0.001).

CONCLUSION

Bovine TB is prevalent in cattle in North Tongu district. Although herdsmen indulge in risky lifestyles that expose them to BTB, a zero prevalence of BTB was observed, further study is envisaged using a larger sample size.

Interpretation Criteria for Comparative Intradermal Tuberculin Test for Diagnosis of Bovine Tuberculosis in Cattle in Maroua Area of Cameroon

Intradermal tuberculin test (TST) is the choice method for diagnosis of bovine tuberculosis (Tb) in live animals. This work was done to assess the performance of single intradermal comparative cervical tuberculin (SICCT) test in randomly selected cattle in Maroua, Cameroon, against detection of Tb lesions and detection of Tb lesions plus acid fast bacilli in lesions. While 22.28% of slaughtered cattle presented Tb lesions at meat inspection, detection rates of anti-bovine-Tb antibody, Tb lesions, and Tb lesions plus acid fast bacilli were 68.57%, 32.95%, and 22.35%, respectively. SICCT-bovine-Tb positive cattle were 35.29%, 29.41%, 25.88%, 24.7%, and 21.18% at ≥2 mm, ≥2.5 mm, ≥3 mm, ≥3.5 mm, and ≥4 mm cut-offs, respectively. Higher sensitivity and predictive values were obtained at severe interpretations. The best performance was at ≥3 mm and ≥3.5 mm cut-offs. Against detection of Tb lesions, ≥3 mm and ≥3.5 mm showed sensitivity of 67.8% and specificity of 94.7% and 96.5%, respectively. For detection of Tb lesions accompanied with acid fast bacilli in lesions, ≥3 mm and ≥3.5 mm showed sensitivity of 89.4% and specificity of 92.4% and 93.9%, respectively. These findings revealed that interpretations of SICCT-bovine-Tb should be at ≥3 mm and/or ≥3.5 mm cut-offs. Severe interpretation of TST is essential for optimal diagnosis of bovine Tb in cattle in Maroua, Cameroon.

The Added-Value of Using Participatory Approaches to Assess the Acceptability of Surveillance Systems: The Case of Bovine Tuberculosis in Belgium

CONTEXT AND OBJECTIVE

Bovine tuberculosis (bTB) surveillance in Belgium is essential to maintain the officially free status and to preserve animal and public health. An evaluation of the system is thus needed to ascertain the surveillance provides a precise description of the current situation in the country. The evaluation should assess stakeholders' perceptions and expectations about the system due to the fact that the acceptability has an influence on the levels of sensitivity and timeliness of the surveillance system. The objective of the study was to assess the acceptability of the bTB surveillance in Belgium, using participatory tools and the OASIS flash tool ('analysis tool for surveillance systems').

METHODS

For the participatory process, focus group discussions and individual interviews were implemented with representatives involved with the system, both from cattle and wildlife part of the surveillance. Three main tools were used: (i) relational diagrams associated with smileys, (ii) flow diagrams associated with proportional piling, and (iii) impact diagrams associated with proportional piling. A total of six criteria were assessed, among which five were scored on a scale from -1 to +1. For the OASIS flash tool, one full day meeting with representatives from stakeholders involved with the surveillance was organised. A total of 19 criteria linked to acceptability were scored on a scale from 0 to 3.

RESULTS AND CONCLUSION

Both methods highlighted a medium acceptability of the bTB surveillance. The main elements having a negative influence were the consequences of official notification of a bTB suspect case in a farm, the low remuneration paid to private veterinarians for execution of intradermal tuberculin tests and the practical difficulties about the containment of the animals. Based on the two evaluation processes, relevant recommendations to improve the surveillance were made. Based on the comparison between the two evaluation processes, the added value of the participatory approach was highlighted.

A review of risk factors for bovine tuberculosis infection in cattle in the UK and Ireland

Bovine tuberculosis (bTB) is an important disease of cattle caused by infection withMycobacterium bovis, a pathogen that may be extremely difficult to eradicate in the presence of a true wildlife reservoir. Our objective was to identify and review relevant literature and provide a succinct summary of current knowledge of risk factors for transmission of infection of cattle. Search strings were developed to identify publications from electronic databases to February 2015. Abstracts of 4255 papers identified were reviewed by three reviewers to determine whether the entire article was likely to contain relevant information. Risk factors could be broadly grouped as follows: animal (including nutrition and genetics), herd (including bTB and testing history), environment, wildlife and social factors. Many risk factors are inter-related and study designs often do not enable differentiation between cause and consequence of infection. Despite differences in study design and location, some risk factors are consistently identified, e.g. herd size, bTB history, presence of infected wildlife, whereas the evidence for others is less consistent and coherent, e.g. nutrition, local cattle movements. We have identified knowledge gaps where further research may result in an improved understanding of bTB transmission dynamics. The application of targeted, multifactorial disease control regimens that address a range of risk factors simultaneously is likely to be a key to effective, evidence-informed control strategies.

Prevalence and risk factors of bovine tuberculosis in dairy cattle in Eritrea

Background

The prevalence of bovine tuberculosis (BTB) in dairy cattle in the three major milk producing regions of Eritrea was assessed by subjecting 15,354 dairy cattle, 50 % of Eritrea’s dairy cattle population, to the single intradermal comparative tuberculin test (SICTT). Skin test results were interpreted according to guidelines of the World Organization for Animal Health (OIE) with >4 mm as cutoff in skin thickness increase. In addition, we studied the relation between ‘physiological’ variables related to pregnancy and lactation, and the variable ‘region’ on the probability to be skin test positive.

Results

The BTB prevalences at animal and herd levels were: 21.5 % and 40.9 % in Maekel, 7.3 % and 10 % in Debub, and 0.2 % and 1.6 % in the Anseba region, respectively. Overall, in the regions included, prevalence was 11.3 % (confidence interval (CI) 95 % CI, 11.29 – 11.31 %) and 17.3 % (95 % CI, 17.27–17.33 %), at animal and herd level, respectively. Considering positive herds only, the animal BTB prevalence was 36.8 %, 30.1 %, and 1.8 %, in Maekel, Debub and Anseba, respectively, and the overall animal prevalence within these herds was 32 %. In adult dairy cattle the probability of positive reactivity in the SICTT test was highest in pregnant animals as compared to the other categories.

Conclusion

This study reports persistent prevalence of BTB as defined by positive SICTT in the dairy sector of Eritrea, especially in the regions of Maekel and Debub that are located in the central highlands of the country. To our understanding this is the first report that has encompassed all the major dairy farms in Eritrea and it will be instrumental in advocating future BTB control programs in the dairy sector.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0705-9) contains supplementary material, which is available to authorized users.

Role of Cattle Movements in Bovine Tuberculosis Spread in France between 2005 and 2014

Live animal movements are a major transmission route for the spread of infectious agents such as Mycobacterium bovis, the main agent of bovine Tuberculosis (bTB). France became officially bTB-free in 2001, but M. bovis is still circulating in the cattle population, with about a hundred of outbreaks per year, most located in a few geographic areas. The aim of this study was to analyse the role of cattle movements in bTB spread in France between 2005 and 2014, using social network analysis and logistic regression models. At a global scale, the trade network was studied to assess the association between several centrality measures and bTB infection though a case-control analysis. The bTB infection status was associated with a higher in-degree (odds-ratio [OR] = 2.4 [1.1–5.4]) and with a higher ingoing contact chain (OR = 2.2 [1.0–4.7]). At a more local scale, a second case-control analysis was conducted to estimate the relative importance of cattle movements and spatial neighbourhood. Only direct purchase from infected herds was shown to be associated with bTB infection (OR = 2.9 [1.7–5.2]), spatial proximity to infected herds being the predominant risk factor, with decreasing ORs when distance increases. Indeed, the population attributable fraction was 12% [5%–18%] for cattle movements and 73% [68%–78%] for spatial neighbourhood. Based on these results, networks of potential effective contacts between herds were built and analysed for the three major spoligotypes reported in France. In these networks, the links representing cattle movements were associated with higher edge betweenness than those representing the spatial proximity between infected herds. They were often links connecting distinct communities and sometimes distinct geographical areas. Therefore, although their role was quantitatively lower than the one of spatial neighbourhood, cattle movements appear to have been essential in the French bTB dynamics between 2005 and 2014.

Molecular detection of Mycobacterium bovis in cattle herds of the state of Pernambuco, Brazil

Background

The present study aimed to direct detect Mycobacterium bovis in milk (n = 401) and blood (n = 401) samples collected from 401 dairy cows of 20 properties located in the state of Pernambuco, Brazil, by real-time quantitative PCR (qPCR) targeting the region of difference 4 (RD4). Risk factors possibly associated with bovine tuberculosis (BTB) were also evaluated.

Results

Of the 802 samples analyzed, one milk (0.25 %) and eight blood (2 %) samples were positive for M. bovis in the qPCR and their identities were confirmed by sequencing. Animals positive for M. bovis were found in six (30 %) of the 20 properties visited. None of the risk factors evaluated were statistically associated with BTB.

Conclusions

M. bovis DNA was detected in one milk sample what may pose a risk to public health because raw milk is commonly consumed in Brazil.

Risk factors associated with Mycobacterium bovis skin positivity in cattle and buffalo in Peshawar, Pakistan

A cross-sectional study was carried out to determine the prevalence of bovine tuberculosis (bTB) and associated risk factors in cattle and buffalo in Peshawar, Pakistan. Cattle and buffalo, randomly selected from all four towns of District Peshawar, were screened for bovine tuberculosis using comparative cervical intradermal tuberculin test (CCIT). For obtaining data on risk factors, sociodemographic condition, animal characteristics, and management, interviewer administered pretested questionnaire to animal owners. Multivariable logistic regression models were used to measure association between risk factors and comparative cervical intradermal tuberculin reactors. A total of 556 cattle and buffalo were screened for bovine tuberculosis. Out of 556 animals screened, 5.75 % (3.9-8.0 %) were found positive. The prevalence was higher in old animals (p = 0.001) as compared to younger animals. Prevalence also varied with source of animal (either raised on farm or purchased), stay of animals at night (indoor or outdoor), and herd size. Farmer's knowledge about transmission of TB from animals to human as well as signs and symptoms of TB was extremely low. Only 3.6 % farmers correctly stated the combination of three major symptoms of TB. Results of the study call for immediate intervention to control bTB in animals as well as its transmission to human population. Furthermore, it is suggested to emphasize on local epidemiology of bTB and husbandry practices of cattle and buffalo during the control program.

Spatial-temporal Variations of Bovine Tuberculosis Incidence in France between 1965 and 2000

We analysed the spatiotemporal variations of bovine tuberculosis (bTB) incidence between 1965 and 2000 in France at the department level (95 areas). Using a Bayesian space-time model, we studied the association between the evolution of bTB incidence and changes of cattle population structure and of herd management practices. Several spatiotemporal hierarchical Bayesian models were compared, and the deviance information criterion was used to select the best of them. Southern France remained a high-risk area over the analysed period, whereas central and western regions were low-risk areas. Besides the frequency of tuberculin skin testing (fixed according to bTB incidence in the preceding years), four factors were associated with an increased risk of bTB: the average herd density and size, the percentage of dairy cows in the cattle population, and the percentage of permanent grassland in cultivated surfaces area. These four factors are linked to the progressive professionalization and specialization of cattle farming, with the disappearance of family farms and of the intensification of breeding systems (especially in dairy farms after the application of the milk quota system in the 1980s). Both trends probably played a significant role in reducing the risk of bTB in France between 1965 and 2000, besides mandatory detection and control procedures.

Prevalence of bovine tuberculosis and risk factor assessment in cattle in rural livestock areas of Govuro District in the Southeast of Mozambique

Background

Bovine 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 findings

A 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/Significance

The 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.

Dilution effect and identity effect by wildlife in the persistence and recurrence of bovine tuberculosis

Current theories on disease-diversity relationships predict a strong influence of host richness on disease transmission. In addition, identity effect, caused by the occurrence of particular species, can also modify disease risk. We tested the richness effect and the identity effects of mammal species on bovine tuberculosis (bTB), based on the regional bTB outbreak data in cattle from 2005-2010 in Africa. Besides, we also tested which other factors were associated with the regional bTB persistence and recurrence in cattle. Our results suggested a dilution effect, where higher mammal species richness (MSR) was associated with reduced probabilities of bTB persistence and recurrence in interaction with cattle density. African buffalo had a positive effect on bTB recurrence and a positive interaction effect with cattle density on bTB persistence, indicating an additive positive identity effect of buffalo. The presence of greater kudu had no effect on bTB recurrence or bTB persistence. Climatic variables only act as risk factors for bTB persistence. In summary, our study identified both a dilution effect and identity effect of wildlife and showed that bTB persistence and recurrence were correlated with different sets of risk factors. These results are relevant for more effective control strategies and better targeted surveillance measures in bTB.

Tuberculosis epidemiology in islands: insularity, hosts and trade

Because of their relative simplicity and the barriers to gene flow, islands are ideal systems to study the distribution of biodiversity. However, the knowledge that can be extracted from this peculiar ecosystem regarding epidemiology of economically relevant diseases has not been widely addressed. We used information available in the scientific literature for 10 old world islands or archipelagos and original data on Sicily to gain new insights into the epidemiology of the Mycobacterium tuberculosis complex (MTC). We explored three nonexclusive working hypotheses on the processes modulating bovine tuberculosis (bTB) herd prevalence in cattle and MTC strain diversity: insularity, hosts and trade. Results suggest that bTB herd prevalence was positively correlated with island size, the presence of wild hosts, and the number of imported cattle, but neither with isolation nor with cattle density. MTC strain diversity was positively related with cattle bTB prevalence, presence of wild hosts and the number of imported cattle, but not with island size, isolation, and cattle density. The three most common spoligotype patterns coincided between Sicily and mainland Italy. However in Sicily, these common patterns showed a clearer dominance than on the Italian mainland, and seven of 19 patterns (37%) found in Sicily had not been reported from continental Italy. Strain patterns were not spatially clustered in Sicily. We were able to infer several aspects of MTC epidemiology and control in islands and thus in fragmented host and pathogen populations. Our results point out the relevance of the intensity of the cattle commercial networks in the epidemiology of MTC, and suggest that eradication will prove more difficult with increasing size of the island and its environmental complexity, mainly in terms of the diversity of suitable domestic and wild MTC hosts.

Bovine tuberculosis surveillance alternatives in Belgium

Belgium obtained the bovine tuberculosis (bTB) officially free status in 2003 (EC Decision 2003/467/EC). This study was carried out to evaluate the components of the current bTB surveillance program in Belgium and to determine the sensitivity of this program. Secondly, alternatives to optimize the bTB surveillance in accordance with European legislation (Council Directive 64/432/EEC) were evaluated. Separate scenario trees were designed for each active surveillance component of the bTB surveillance program. Data from 2005 to 2009 regarding cattle population, movement and surveillance were collected to feed the stochastic scenario tree simulation model. A total of 7,403,826 cattle movement history records were obtained for the 2,678,020 cattle from 36,059 cattle herds still active in 2009. The current surveillance program sensitivity as well as the impact of alternative surveillance protocols was simulated in a stochastic model using 10,000 iterations per simulation. The median (50% percentile) of the component sensitivities across 10,000 iterations was 0.83, 0.85, 0.99, 0.99, respectively, for (i) testing the cattle only during the winter screening, (ii) testing only imported cattle, (iii) testing only purchased cattle and (iv) testing only all slaughtered cattle. The sensitivity analysis showed that the most influential input parameter explaining the variability around the output came from the uncertainty distribution around the sensitivity of the diagnostic tests used within the bTB surveillance. Providing all animals are inspected and post mortem inspection is highly sensitive, slaughterhouse surveillance was the most effective surveillance component. If these conditions were not met, the uncertainty around the mean sensitivity of this component was important. Using an antibody ELISA at purchase and an interferon gamma test during winter screening and at import would increase greatly the sensitivity and the confidence level of Belgium's freedom from bTB infection status.