Bovine Tuberculosis Infection Research Articles

Differentiation of Bovine Tuberculosis and Paratuberculosis Infections with Antemortem Diagnostic Methods

In this study, based on the results of tuberculin skin tests (Bovine and Avian PPD) used in the antemortem diagnosis and differentiation of Bovine Tuberculosis, the animals in the farms with suspected Tuberculosis were serologically examined to diagnose Paratuberculosis infection and fecal bacterioscopy was performed. In addition, it was aimed to obtain data that will contribute to the eradication studies of Bovine Tuberculosis disease by comparing the antemortem diagnostic methods of Bovine Tuberculosis disease, which is endemic in Türkiye and by determining the sensitivity and specificity values of the interferon gamma (IFN-γ) test. In this context, intradermal tuberculin test was applied to 423 cattle with suspected Tuberculosis in a total of 5 dairy cattle farms, one each from Çankırı, Çorum, Ankara, Eskişehir and Konya regions, and this test was determined as the gold standard method and the sensitivity and specificity of the IFN-γ test were determined as 86% and 97%, respectively. For the diagnosis of Paratuberculosis infection, antibody ELISA, fecal bacterioscopy and IFN-γ ELISA were performed on these animals and the prevalence of these tests were 10.4%, 5.44% and 4.96% respectively and 4 (0.95%) of the cattle were positive for each of the diagnostic methods for Map infection. As a result, it was concluded that IFN-γ test, which gives similar results to intradermal tuberculin test results, can also be used in the antemortem diagnosis of Bovine Tuberculosis. Also, in the comparative intradermal tuberculin test for the diagnosis of Tuberculosis infection, avian PPD positive animals were found to play a decisive role in the detection of nonspecific reactions or Paratuberculosis infected animals, supported by other tests used for the diagnosis of Paratuberculosis.

Prevalence and risk factors of bovine tuberculosis in cattle in selected districts of Fafan pastoral settings, Eastern Ethiopia

Cross-sectional study was conducted from October 2021 to August 2022 to investigate the prevalence and associated risk factors of bovine tuberculosis in cattle in selected districts of the pastoral settings of Fafan zone, Somali region, eastern Ethiopia. A comparative intradermal tuberculin test was performed using purified protein derivatives. Animal-related characteristics, and the owner's knowledge on the importance of BTB were collected using a structured questionnaire. The prevalence was 11.24 % (95 % CI, 8.61–14.35) and 43.3 % (95 % CI, 33.27–53.75) at the individual and herd levels, respectively. There were statistically significant differences in the proportions of positive reactor animals according to body condition score (P = 0.000), age (P = 0.048), seasonal migration (P = 0.038), parity number (P = 0.005), and reproductive status (P = 0.037). Animals with poor body condition scores had a significantly higher likelihood of testing positive, with their odds being 11.4 times greater (COR = 11.408, CI = 3.43–37.94, P < 0.001). In multivariate logistic regression, poor body condition score remained significantly associated with the odds of a positive reaction to tuberculosis (AOR = 0.137, CI = 0.053–0.356, P < 0.001). Similarly, the analysis showed that seasonal migration (AOR = 2.882, CI = 1.155–7.191, P = 0.023) and parity number (AOR = 11.64, CI = 1.818–74.464, P = 0.010) were significant predictors of bovine tuberculosis infection in cattle. According to the questionnaire, 14.2 % (17 of 120) and 13.3 % (16 of 120) of the respondents were knowledgeable about bovine tuberculosis and its transmission from animals to humans, and vice versa, respectively. The general judgment of herders' understanding of bovine tuberculosis transmission methods to humans was very low. The study findings showed a high prevalence of bovine tuberculosis in the study area, emphasizing the need for an effective control and prevention strategy.

Evaluation of the diagnostic accuracy of the serological test for paratuberculosis in cattle according to tuberculosis status.

Enzyme-linked immunosorbent assays (ELISAs) are the most widely used diagnostic tools in bovine paratuberculosis (bPTB) control. However, their diagnostic accuracy may be compromised by bovine tuberculosis (bTB) infection, as both diseases share diagnostic targets. The bPTB and bTB infection status of 228 animals was determined using microbiological tissue culture as a reference test. The diagnostic performance (sensitivity, specificity, likelihood ratios and predictive values) of the bPTB-ELISA on blood serum samples, taking into account the bPTB animal-level prevalence of the area and the bTB status of the animals, was evaluated. A sensitivity of 40.7% (95% confidence interval [CI]: 27.5%-53.9%) and a specificity of 94.7% (95% CI: 91.4%-98.0%) were obtained for bPTB-ELISA in all animals. A bPTB-ELISA-positive animal would have a post-test probability of 70% or more of being infected in areas with a bPTB prevalence of 23% or more. A negative bPTB-ELISA result, in areas with a bPTB prevalence of 41% or less, would rule out the disease with more than 70% certainty. In bTB-positive animals, sensitivity increased (94.4% [95% CI: 81.4%-100%] vs. 25.1% [95% CI: 11.8%-38.4%]) and specificity decreased (82.6% [95% CI: 71.8%-93.4%] vs. 99.4% [95% CI: 98.0%-99.9%]). The bPTB-ELISA is a good tool to rule out bPTB co-infection in bTB-positive animals, while in bTB-negative animals, it allows confirmation of disease with more than 70% probability if disease prevalence is 6% or more. The observed differences could be enhanced by the effect of frequent application of the intradermal tuberculin test, which was unknown in the animals studied. These results provide useful guidance for the application and interpretation of ELISA as a tool for bPTB disease control.

Putative volatile biomarkers of bovine tuberculosis infection in breath, skin and feces of cattle.

Bovine tuberculosis (bTB) is an infectious disease with significant impact on animal health, public health and international trade. Standard bTB screening in live cattle consists in injecting tuberculin and measuring the swelling at the place of injection few days later. This procedure is expensive, time-consuming, logistically challenging, and is not conclusive before performing confirmatory tests and additional analysis. The analysis of the volatile organic compounds (VOCs) emitted by non-invasive biological samples can provide an alternative diagnostic approach suitable for bTB screening. In the present study, we analyzed VOC samples emitted through the breath, feces and skin of 18 cows diagnosed with bTB from three farms from Romania, as well as of 27 negative cows for bTB from the same farms. Analytical studies employing gas chromatography coupled to mass spectrometry revealed 80 VOCs emitted through the breath, 200 VOCs released by feces, and 80 VOCs emitted through the skin. Statistical analysis of these compounds allowed the identification of 3 tentative breath VOC biomarkers (acetone; 4-methyldecane; D-limonene), 9 tentative feces VOC biomarkers (toluene; [(1,1-dimethylethyl)thio]acetic acid; alpha-thujene; camphene; phenol; o-cymene; 3-(1,1-dimethylethyl)-2,2,4,4-tetramethyl-3-pentanol; 2,5-dimethylhexane-2,5-dihydroperoxide; 2,4-di-tert-butylphenol), and 3 tentative skin VOC biomarkers (ammonia; 1-methoxy-2-propanol; toluene). The possible pathway of these volatile biomarkers is discussed.

Deletion in KARLN intron 5 and predictive relationship with bovine tuberculosis and brucellosis infection phenotype.

Kalirin (gene: KALRN) is a Rho-GEF kinase linked to neurodegenerative diseases in humans. Unexpectedly, various polymorphisms in KALRN gene were previously associated with resistance to bacterial infections in ruminants. In this study, we evaluated the effect of the rs384223075 (RS-075) deletion in KALRN intron 5 on the occurrence of Mycobacterium bovis and Brucella abortus infections in cattle. We performed two separate case-control association analyses: one for bovine tuberculosis (bTB) using 308 Holstein and Jersey cows from three herds with prevalence between 5 and 15% for this infection; and another for brucellosis using 140 Holstein and beef crossbred cows from two herds with high prevalence for brucellosis (> 30%). In the bTB analysis, the RS-075 deletion frequency was higher among cases than controls (p = 0.0001), and the absence of the RS-075 deletion allele was associated with negative PPD-skin test results (p = 0.0009) at genotype level. On the contrary, RS-075 was not associated with Brucella spp. serological status (p = 0.72) but, unexpectedly, the deletion allele was more frequent among controls than cases in the beef crossbred herd (0.31 vs. 0.14, p = 0.02). In concordance with this observation, in vitro assays showed that the RS-075 deletion could be linked to an enhanced cellular response to bacterial antigens and unspecific stimulation in mononuclear cells derived from beef crossbred cows, specifically the reactive nitrogen species production (p = 0.008) and proliferation capacity (p = 0.018). This study is consistent with other reports that support an important role of the KALRN gene and its polymorphisms in the host response to intracellular pathogens.

Highlighting on Bovine Tuberculosis infection in cattle

Highlighting on Bovine Tuberculosis infection in cattle

Epidemiological Problems and Solution Analysis of Bovine Tuberculosis Infection in Turkey

Türkiye’de Sığır Tüberkülozu (bTB), sığır sürülerinde endemik bir seyir izlemektedir. Bugüne kadar, hastalıkla mücadele amacıyla yürütülen çalışmalardan çeşitli nedenlerden dolayı istenen sonuç elde edilememiştir. Sığır Tüberkülozu mihrak sayıları son yıllarda artmaya devam etmektedir. Bu süreç, ülkemiz hayvan sağlığı ve halk sağlığı için risk artışını, damızlık hayvan kaybını ve sosyo ekonomik kaybı beraberinde getirmektedir. Bu çalışmayla ülkesel olarak sahada bu artışın nedeni olan sorunlar epidemiyolojik olarak belirlenmeye çalışılmıştır. Ayrıca tespit edilen sorunların elde edilen bilgiler ışığında çözüm analizi yapılıp öneriler sunularak, mevcut ulusal mücadele stratejisinin geliştirilmesine katkı sağlanması ve hastalıkla mücadelede politika oluşturma sürecine rehberlik edilmesi amaçlanmıştır. Sığır Tüberkülozu hastalığının doğası ve Türkiye’nin şartları düşünüldüğünde hastalık prevalansının azaltılması için mücadelenin zorlu ve maliyetli olacağı anlaşılmaktadır. Bu çalışma sonucunda, sadece bu işe odaklanacak bir veteriner hizmetleri teşkilat yapısının yeniden oluşturulup, tüm paydaşlarla birlikte uzun sürede ve sabırla yürütülecek bir çalışmayla hastalığın prevalansı azaltılıp, kademeli ari bölgeler oluşturularak başarıya ulaşılacağı kanaatine varılmıştır.

Public health and economic benefits of spotted hyenas Crocuta crocuta in a peri‐urban system

Abstract Species that depend on anthropogenic waste for food can remove pathogens that pose health risks to humans and livestock, thereby saving lives and money. Quantifying these benefits is rare, yet can lead to innovative conservation solutions. To assess these benefits, we examined the feeding ecology and population size of peri‐urban spotted hyenas Crocuta crocuta in Mekelle, Ethiopia. We integrated these field data into a disease transmission model to predict: (a) the number of anthrax and bovine tuberculosis (bTB) infections arising in humans and livestock from infected carcass waste and (b) the costs associated with treating these infections and losing livestock. We compared these public health and economic outcomes under two scenarios: (a) hyenas are present and (b) the counterfactual, hyenas are absent. We estimated that hyenas annually remove 4.2% (207 tonnes) of the total carcass waste disposed of by residents and businesses in Mekelle. Furthermore, the scavenging behaviour of hyenas annually prevents five infections of anthrax and bTB in humans, and 140 infections in cattle, sheep and goats. This disease control service potentially saves USD 52,165 due to the treatment costs and livestock loss avoided. Synthesis and applications. This human–hyena interaction in Ethiopia is evidence that large carnivores can contribute to human health and economy. To retain these benefits and maintain tolerance of hyenas, we recommend introducing education programmes to promote safe outdoor behaviour around hyenas, training watchdogs to alert residents of hyena presence, constructing bomas to protect livestock from hyena attacks, and preserving the hyenas' access to carcass waste to reduce their dependency on livestock predation. With humans and carnivores coming more frequently into contact, understanding and communicating how these species can benefit humanity will be critical to motivating human–carnivore coexistence worldwide.

Detection of Mycobacterium bovis in environmental samples using nested PCR

The detection of Mycobacterium bovis (M. bovis) in environmental samples with precision is imperative to control bovine tuberculosis (bTB) infections at the herd level, as residual M. bovis remains one of the major causes of recurring infections. In this study, a nested PCR method for the detection of M. bovis in environmental samples was applied to identify potential environmental reservoirs of the bacterium. A set of 200 environmental samples (167 fecal samples and 33 water samples) from 39 herds with a history of bTB outbreak was analyzed using a nested PCR method to detect residual M. bovis. Amplicon libraries of the IS6110 target gene fragment were amplified from M. bovis DNA using two established primer sets. A positive nested PCR result was observed in 69.5% of fecal samples and 66.7% of water samples, thus showing that residual M. bovis was present in the environmental samples of bTB-positive herds in a high proportion. This study is the first to demonstrate high levels of M. bovis DNA in environmental samples and to show that environmental reservoirs of this pathogen contribute to recurring outbreaks of bTB. Environmental monitoring of herds in which bTB outbreaks have occurred with high sensitivity and specificity is expected to help prevent the recurrence of potential bTB disease and improve the herd environment.

Natural resistance to worms exacerbates bovine tuberculosis severity independently of worm coinfection

Pathogen interactions arising during coinfection can exacerbate disease severity, for example when the immune response mounted against one pathogen negatively affects defense of another. It is also possible that host immune responses to a pathogen, shaped by historical evolutionary interactions between host and pathogen, may modify host immune defenses in ways that have repercussions for other pathogens. In this case, negative interactions between two pathogens could emerge even in the absence of concurrent infection. Parasitic worms and tuberculosis (TB) are involved in one of the most geographically extensive of pathogen interactions, and during coinfection worms can exacerbate TB disease outcomes. Here, we show that in a wild mammal natural resistance to worms affects bovine tuberculosis (BTB) severity independently of active worm infection. We found that worm-resistant individuals were more likely to die of BTB than were nonresistant individuals, and their disease progressed more quickly. Anthelmintic treatment moderated, but did not eliminate, the resistance effect, and the effects of resistance and treatment were opposite and additive, with untreated, resistant individuals experiencing the highest mortality. Furthermore, resistance and anthelmintic treatment had nonoverlapping effects on BTB pathology. The effects of resistance manifested in the lungs (the primary site of BTB infection), while the effects of treatment manifested almost entirely in the lymph nodes (the site of disseminated disease), suggesting that resistance and active worm infection affect BTB progression via distinct mechanisms. Our findings reveal that interactions between pathogens can occur as a consequence of processes arising on very different timescales.

Epidemiological Investigation of Bovine Tuberculosis Infection Dynamics in Turkey

A national epidemiological research project was carried out to define the dynamics affecting the epidemiology of bovine tuberculosis (bTB) infection in Turkey and to identify the risk factors. Official veterinarian (OV) and breeder original questionnaires were produced separately as part of this study to collect thorough data regarding the disease from the field. The number of questionnaires that needed to be filled out was decided by 95% confidence interval (CI) and 5% margin of error. The findings of 371 OV and 317 breeder questionnaires completed online across the country were analyzed. In addition, 28 outbreaks determined by random method were visited. To observe regional differences and field conditions, the opinions of OVs who monitored the disease and breeders were compiled. It was observed that the data obtained from both questionnaires was largely compatible. The main factors in the epidemiology of bTB infection were found to be effective fight, development of state policy, providing adequate financing, animal purchase, ear tagging and records, animal traders, animal markets, animal movements, conditional slaughtering, slaughterhouses, postmortem inspection, premise conditions, socio-economic impact, evaluation of raw milk, disease-free premises, compensation payments, and quarantine processes.

INCIDENCE AND CONTROL OF INFECTIOUS BACTERIA IN BOVINE MILK

Milk is an essential source for the ingredients needed for infant growth and adult health. Healthy milk production is important for consumer safety. The aim of the present review article was to highlight on the incidence and control of the infectious bacteria in bovine milk. Raw bovine milk is considered as a vehicle for many infectious bacterial diseases such as Bovine Tuberculosis, Brucellosis, Leptospirosis and Mycoplasma infection. The main microorganisms which isolated from bovine milk in cows with mastitis were Escherichia coli, Staphylococcus aureus, Streptococcus spp., Streptococcus agalactiae, Pasteurella spp., Klebsiella spp., Pseudomonas spp. and Streptococcus dysgalactiae. Early and accurate diagnosis is necessary for achieving successful control programs against the infectious bacteria in bovine milk. For successful control of the infectious bacterial diseases in bovine milk, it is mandatory to follow preventive measures such as proper hygienic procedures regarding animal husbandry and handling, providing the cows with balanced nutrition, following vaccination programs against bacterial diseases, reporting of the notifiable diseases to the health authorities, meticulous inspection of the consistency and color of milk and pasteurization of milk. Vaccination programs provide protection of dairy farm animals by preventing or reducing bacterial infections which in turn can help safeguard dairy industry. The main treatment protocol of bacterial diseases in dairy cows is by using suitable antibiotics, so it is necessary to carry out drug sensitivity test before choosing the proper antibiotic. However, multidrug resistance (MDR) has become a growing threat regards the management of infectious bacterial diseases. Therefore, the introduction of alternative antimicrobial agents such as herbal treatment, probiotics, nanoparticles, and stem cells therapy is of absolute necessity to guard against bacterial multidrug resistance. Also, animal vaccinations are important tools for protection against many infectious bacterial diseases affecting bovine milk.

Bovine tuberculosis and brucellosis in Livestock at the Greater Ruaha Ecosystem

A cross-sectional study was conducted to determine the prevalence of bovine tuberculosis (BTB) and the seroprevalence of brucellosis in livestock at the Greater Ruaha Ecosystem in Tanzania. The study further characterized the Mycobacterium spp. from the slaughtered livestock. A questionnaire survey conducted to assess potential herd-level risk factors for BTB and brucellosis revealed that the respondents’ ethnicity and herd mixing were the significant risk factors. Twenty-eight percent of 102 cattle herds had at least one positive or suspect BTB reactor. The overall prevalence of BTB infection in the cattle was 1.32% (18/1368). Forty-two percent of 93 flocks of the small ruminants had at least one brucellosis seropositive animal. The overall seroprevalence of brucellosis in the cattle and small ruminants was 6.6%. Although the prevalence of both diseases was relatively low for individual animals, herd-level prevalence was high suggesting that infection is widespread in the study area and a significant number of households are at risk. Mycobacterium bovis strain identified via polymerase chain reaction (PCR) was confirmed by spoligotyping as spoligotype SB0133. This cattle strain of M.bovis was similar to previously reported involving wild animals in adjacent protected areas. Isolation of identical M. bovis from wildlife and livestock and the demonstration of Brucella spp. seroprevalence in livestock in the same interface, strongly suggest livestock-wildlife interspecies sharing of these pathogens. Occurrence of the microorganisms poses a serious challenge to disease management strategies in pastoralist communities in the interface area

Phylogenomic Perspective on a Unique Mycobacterium bovis Clade Dominating Bovine Tuberculosis Infections among Cattle and Buffalos in Northern Brazil

Lack of routine surveillance in countries endemic for bovine tuberculosis (TB) and limited laboratory support contributes to the inability to differentiate the Mycobacterium tuberculosis Complex species, leading to an underestimated burden of the disease. Here, Whole-Genome Sequencing of Mycobacterium bovis isolated from tissues with TB-like lesions obtained from cattle and buffalos at Marajó Island, Brazil, demonstrates that recent transmission of M. bovis is ongoing at distinct sites. Moreover, the M. bovis epidemiology in this setting is herein found to be dominated by an endemic and unique clade composed of strains evolved from a common ancestor that are now genetically differentiated from other M. bovis clades. Additionally, envisioning a rapid strain differentiation and tracing across multiple settings, 28 globally validated strain-specific SNPs were identified, three of which considered as robust markers for the M. bovis Marajó strain. In conclusion, this study contributes with data regarding the identification of a novel M. bovis phylogenetic clade responsible for ongoing transmission events in both cattle and buffalo species in Brazil, provides a framework to investigate the dissemination of this highly prevalent strain and, holds the potential to inform TB control strategies that may help to prevent the spread of bovine and zoonotic TB.

Histopathological and Molecular Investigation of Natural Cases of Bovine Tuberculosis Infection in Cattle

Bovine tuberculosis (bTB), a chronic infection in cattle caused by Mycobacterium tuberculosis/bovis, that impacts productivity and represents a major public health threat. Although the considerable economic costs and zoonotic risk consequences associated with the disease, accurate estimates of bTB prevalence are lacking in many countries, including India. Therefore, in the current study for collection of tubercular lesions the postmortem examination of 100 cattle was conducted. All major viscera and regional lymph nodes were examined and incised. Histopathology was performed in the cases where gross lesions were suggestive of tuberculosis. PCR was performed on the tissue and faecal samples by using IS6110 insertion sequence, Mycobacterium tuberculosis/bovis complex PCR kit. In 12 animals, nodular lesions with casseating mass suggestive of tuberculosis were observed in the lung tissue. All the 12 lung impression smear and only five faecal smear showed acid fast bacilli stained by Ziehl-Neelsen staining. Histologic features comprised a classic granuloma as a characteristic lesion of tuberculosis composed of a central caseous necrosis with mantle of macrophages, lymphocytes, plasma cells, epithelioid macrophages and Langhan's giant cells and were observed in all 12 cases. All the tissue samples and 11 faecal samples were positive for the Mycobacterium tuberculosis complex using IS6110 sequence. 8 tissue samples and 4 faecal samples were positive by using Mycobacterium tuberculosis/bovis complex PCR kit. It can be concluded that there was good agreement between histopathology, acid fast staining and PCR. It can also be concluded that faecal samples which are easier to collect should be preferred for diagnosis of TB by PCR in cattle.

A comparison between indirect ELISA and tuberculin skin test in the diagnosis of bovine tuberculosis in Kenya

Bovine tuberculosis (BTB) is an important zoonotic disease which has remained persistent in many areas of the World. Control and eradication has proved problematic due to the challenges in effective screening and diagnosis. Limited information on the status of BTB in Kenya presents a need to investigate its occurrence in cattle population. The study was carried out using an indirect antibody Enzyme Linked Immunosorbent Assay (ELISA-IDEXX-USA) to assess the agreement with Comparative Intradermal Tuberculin Test (CITT) test results between August and December 2013 in Laikipia County. The study also determined the apparent prevalence of cattle BTB antibodies in Laikipia County. A total of 276 bovine serum samples were tested using MPB70 and MPB83 recombinant proteins as capture antigens in the ELISA kit. Data were recorded in Microsoft Excel and exported to SPSS 16.0 for analysis. Apparent prevalence was calculated as a proportion at 95% CI, Kappa statistics computed, and test of significance assessed by Chi-square and Fisher exact test. The results showed an individual animal apparent prevalence of 3.9% (11/276) and a herd prevalence of 58.3% (7/12). There was no significant association between BTB infection and both animal level factors, breed and sex. Kappa agreement test between ELISA test and TST showed a good agreement at K= 0.65. This study reported the prevalence of BTB in cattle for the first time in Laikipia County Kenya using the IDEXX ELISA. The ELISA test was comparable to the tuberculin test which is used as the gold standard for screening TB on live animals. The two tests can be used alongside for series or parallel interpretation to achieve desirable diagnostic sensitivity and specificity in disease control programs.

A comparison between indirect ELISA and tuberculin skin test in the diagnosis of bovine tuberculosis in Kenya

Bovine tuberculosis (BTB) is an important zoonotic disease which has remained persistent in many areas of the World. Control and eradication has proved problematic due to the challenges in effective screening and diagnosis. Limited information on the status of BTB in Kenya presents a need to investigate its occurrence in cattle population. The study was carried out using an indirect antibody Enzyme Linked Immunosorbent Assay (ELISA-IDEXX-USA) to assess the agreement with Comparative Intradermal Tuberculin Test (CITT) test results between August and December 2013 in Laikipia County. The study also determined the apparent prevalence of cattle BTB antibodies in Laikipia County. A total of 276 bovine serum samples were tested using MPB70 and MPB83 recombinant proteins as capture antigens in the ELISA kit. Data were recorded in Microsoft Excel and exported to SPSS 16.0 for analysis. Apparent prevalence was calculated as a proportion at 95% CI, Kappa statistics computed, and test of significance assessed by Chi-square and Fisher exact test. The results showed an individual animal apparent prevalence of 3.9% (11/276) and a herd prevalence of 58.3% (7/12). There was no significant association between BTB infection and both animal level factors, breed and sex. Kappa agreement test between ELISA test and TST showed a good agreement at K= 0.65. This study reported the prevalence of BTB in cattle for the first time in Laikipia County Kenya using the IDEXX ELISA. The ELISA test was comparable to the tuberculin test which is used as the gold standard for screening TB on live animals. The two tests can be used alongside for series or parallel interpretation to achieve desirable diagnostic sensitivity and specificity in disease control programs.

Immune stability predicts tuberculosis infection risk in a wild mammal.

Immunity is one of the most variable phenotypic traits in animals; however, some individuals may show less fluctuation in immune traits, resulting in stable patterns of immune variation over time. It is currently unknown whether immune variation has consequences for infectious disease risk. In this study, we identified moderately stable immune traits in wild African buffalo and asked whether the stability of these traits affected bovine tuberculosis (TB) infection risk. We found that adaptive immune traits such as the level of interferon-γ (IFN-γ) released after white blood cell stimulation, the number of circulating lymphocytes and the level of antibodies against bovine adenovirus-3 were moderately repeatable (i.e. stable) over time, whereas parameters related to innate immunity either had low repeatability (circulating eosinophil numbers) or were not repeatable (e.g. neutrophil numbers, plasma bacteria killing capacity). Intriguingly, individuals with more repeatable IFN-γ and lymphocyte levels were at a significantly higher risk of acquiring TB infection. In stark contrast, average IFN-γ and lymphocyte levels were poor predictors of TB risk, indicating that immune variability rather than absolute response level better captured variation in disease susceptibility. This work highlights the important and under-appreciated role of immune variability as a predictor of infection risk.

Spatially correlated binary data modelling using generalized estimating equations with alternative hypersphere decomposition

For correlated binary data, generalized estimating Equation (GEE) approach is commonly used for inference of the mean parameters. When the associated correlation is of interest, e.g., in spatial data analysis, some traditional correlation structures such as compound symmetry and AR(1) were employed in the literature, which is not appropriate for the inherent correlation for correlated binary data. In this paper, we proposed another set of GEE implemented with alternative hypersphere decomposition (AHPC) to model the correlation parameters. An iterative algorithm is provided to estimate the mean and correlation parameters simultaneously. By utilizing the AHPC, we developed a parametrization for the correlation matrix that automatically ensures the order independence and non-negative definiteness. We also addressed the issue of asymptotic properties. For illustration, the proposed methods were used to fit a spatial bovine tuberculosis infection data in Ireland, aiming to analyse the influential factors which affect the infection of cattle and/or badgers.

Network analysis of dairy cattle movement and associations with bovine tuberculosis spread and control in emerging dairy belts of Ethiopia

BackgroundDairy cattle movement could be a major risk factor for the spread of bovine tuberculosis (BTB) in emerging dairy belts of Ethiopia. Dairy cattle may be moved between farms over long distances, and hence understanding the route and frequency of the movements is essential to establish the pattern of spread of BTB between farms, which could ultimately help to inform policy makers to design cost effective control strategies. The objective of this study was, therefore, to investigate the network structure of dairy cattle movement and its influence on the transmission and prevalence of BTB in three emerging areas among the Ethiopian dairy belts, namely the cities of Hawassa, Gondar and Mekelle.MethodsA questionnaire survey was conducted in 278 farms to collect data on the pattern of dairy cattle movement for the last 5 years (September 2013 to August 2018). Visualization of the network structure and analysis of the relationship between the network patterns and the prevalence of BTB in these regions were made using social network analysis.ResultsThe cattle movement network structure display both scale free and small world properties implying local clustering with fewer farms being highly connected, at higher risk of infection, with the potential to act as super spreaders of BTB if infected. Farms having a history of cattle movements onto the herds were more likely to be affected by BTB (OR: 2.2) compared to farms not having a link history. Euclidean distance between farms and the batch size of animals moved on were positively correlated with prevalence of BTB. On the other hand, farms having one or more outgoing cattle showed a decrease on the likelihood of BTB infection (OR = 0.57) compared to farms which maintained their cattle.ConclusionThis study showed that the patterns of cattle movement and size of animal moved between farms contributed to the potential for BTB transmission. The few farms with the bulk of transmission potential could be efficiently targeted by control measures aimed at reducing the spread of BTB. The network structure described can also provide the starting point to build and estimate dynamic transmission models for BTB, and other infectious diseases.