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"Allen, Adrian R."
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Does Mycobacterium tuberculosis var. bovis Survival in the Environment Confound Bovine Tuberculosis Control and Eradication? A Literature Review
by
Ford, Tom
,
Allen, Adrian R.
,
Skuce, Robin A.
in
Adaptation
,
Animal feeding and feeds
,
Animal models
2021
Bovine tuberculosis (bTB) is one of the globe’s most common, multihost zoonoses and results in substantial socioeconomic costs for governments, farming industries, and tax payers. Despite decades of surveillance and research, surprisingly, little is known about the exact mechanisms of transmission. In particular, as a facultative intracellular pathogen, to what extent does survival of the causative agent, Mycobacterium tuberculosis var. bovis (M. bovis), in the environment constitute an epidemiological risk for livestock and wildlife? Due largely to the classical pathology of cattle cases, the received wisdom was that bTB was spread by direct inhalation and exchange of bioaerosols containing droplets laden with bacteria. Other members of the Mycobacterium tuberculosis complex (MTBC) exhibit differing host ranges, an apparent capacity to persist in environmental fomites, and they favour a range of different transmission routes. It is possible, therefore, that infection from environmental sources of M. bovis could be a disease transmission risk. Recent evidence from GPS-collared cattle and badgers in Britain and Ireland suggests that direct transmission by infectious droplets or aerosols may not be the main mechanism for interspecies transmission, raising the possibility of indirect transmission involving a contaminated, shared environment. The possibility that classical pulmonary TB can be simulated and recapitulated in laboratory animal models by ingestion of contaminated feed is a further intriguing indication of potential environmental risk. Livestock and wildlife are known to shed M. bovis onto pasture, soil, feedstuffs, water, and other fomites; field and laboratory studies have indicated that persistence is possible, but variable, under differing environmental conditions. Given the potential infection risk, it is timely to review the available evidence, experimental approaches, and methodologies that could be deployed to address this potential blind spot and control point. Although we focus on evidence from Western Europe, the concepts are widely applicable to other multihost bTB episystems.
Journal Article
Genomic Prediction for Tuberculosis Resistance in Dairy Cattle
by
Tsairidou, Smaragda
,
Matika, Oswald
,
McBride, Stewart H.
in
Animal breeding
,
Animals
,
Area Under Curve
2014
The increasing prevalence of bovine tuberculosis (bTB) in the UK and the limitations of the currently available diagnostic and control methods require the development of complementary approaches to assist in the sustainable control of the disease. One potential approach is the identification of animals that are genetically more resistant to bTB, to enable breeding of animals with enhanced resistance. This paper focuses on prediction of resistance to bTB. We explore estimation of direct genomic estimated breeding values (DGVs) for bTB resistance in UK dairy cattle, using dense SNP chip data, and test these genomic predictions for situations when disease phenotypes are not available on selection candidates.
We estimated DGVs using genomic best linear unbiased prediction methodology, and assessed their predictive accuracies with a cross validation procedure and receiver operator characteristic (ROC) curves. Furthermore, these results were compared with theoretical expectations for prediction accuracy and area-under-the-ROC-curve (AUC). The dataset comprised 1151 Holstein-Friesian cows (bTB cases or controls). All individuals (592 cases and 559 controls) were genotyped for 727,252 loci (Illumina Bead Chip). The estimated observed heritability of bTB resistance was 0.23±0.06 (0.34 on the liability scale) and five-fold cross validation, replicated six times, provided a prediction accuracy of 0.33 (95% C.I.: 0.26, 0.40). ROC curves, and the resulting AUC, gave a probability of 0.58, averaged across six replicates, of correctly classifying cows as diseased or as healthy based on SNP chip genotype alone using these data.
These results provide a first step in the investigation of the potential feasibility of genomic selection for bTB resistance using SNP data. Specifically, they demonstrate that genomic selection is possible, even in populations with no pedigree data and on animals lacking bTB phenotypes. However, a larger training population will be required to improve prediction accuracies.
Journal Article
Field-Isolated Genotypes of Mycobacterium bovis Vary in Virulence and Influence Case Pathology but Do Not Affect Outbreak Size
by
Allen, Adrian R.
,
Bermingham, Mairead L.
,
Wright, David M.
in
Animal husbandry
,
Animal populations
,
Animals
2013
Strains of many infectious agents differ in fundamental epidemiological parameters including transmissibility, virulence and pathology. We investigated whether genotypes of Mycobacterium bovis (the causative agent of bovine tuberculosis, bTB) differ significantly in transmissibility and virulence, combining data from a nine-year survey of the genetic structure of the M. bovis population in Northern Ireland with detailed records of the cattle population during the same period. We used the size of herd breakdowns as a proxy measure of transmissibility and the proportion of skin test positive animals (reactors) that were visibly lesioned as a measure of virulence. Average breakdown size increased with herd size and varied depending on the manner of detection (routine herd testing or tracing of infectious contacts) but we found no significant variation among M. bovis genotypes in breakdown size once these factors had been accounted for. However breakdowns due to some genotypes had a greater proportion of lesioned reactors than others, indicating that there may be variation in virulence among genotypes. These findings indicate that the current bTB control programme may be detecting infected herds sufficiently quickly so that differences in virulence are not manifested in terms of outbreak sizes. We also investigated whether pathology of infected cattle varied according to M. bovis genotype, analysing the distribution of lesions recorded at post mortem inspection. We concentrated on the proportion of cases lesioned in the lower respiratory tract, which can indicate the relative importance of the respiratory and alimentary routes of infection. The distribution of lesions varied among genotypes and with cattle age and there were also subtle differences among breeds. Age and breed differences may be related to differences in susceptibility and husbandry, but reasons for variation in lesion distribution among genotypes require further investigation.
Journal Article
Internet cognitive–behavioural treatment for panic disorder: randomised controlled trial and evidence of effectiveness in primary care
2016
Internet cognitive-behavioural therapy (iCBT) for panic disorder of up to 10 lessons is well established. The utility of briefer programmes is unknown.
To determine the efficacy and effectiveness of a five-lesson iCBT programme for panic disorder.
Study 1 (efficacy): Randomised controlled trial comparing active iCBT (
=27) and waiting list control participants (
=36) on measures of panic severity and comorbid symptoms. Study 2 (effectiveness): 330 primary care patients completed the iCBT programme under the supervision of primary care practitioners.
iCBT was significantly more effective than waiting list control in reducing panic (
=0.97, 95% CI 0.34 to 1.61), distress (
=0.92, 95% CI 0.28 to 1.55), disability (
=0.81, 95% CI 0.19 to 1.44) and depression (
=0.79, 95% CI 0.17 to 1.41), and gains were maintained at 3 months post-treatment (iCBT group). iCBT remained effective in primary care, but lower completion rates were found (56.1% in study 2
. 63% in study 1). Adherence appeared to be related to therapist contact.
The five-lesson Panic Program has utility for treating panic disorder, which translates to primary care. Adherence may be enhanced with therapist contact.
None.
© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.
Journal Article
Internet-delivered cognitive behaviour therapy for post-traumatic stress disorder: a randomised controlled trial and outcomes in routine care
by
Mahoney, Alison E. J.
,
Allen, Adrian R.
,
Newby, Jill M.
in
Anxiety
,
Anxiety disorders
,
Automation
2022
Background:Despite its potential scalability, little is known about the outcomes of internet-based cognitive behaviour therapy (iCBT) for post-traumatic stress disorder (PTSD) when it is provided with minimal guidance from a clinician.Aim:To evaluate the outcomes of minimally guided iCBT for PTSD in a randomised control trial (RCT, Study 1) and in an open trial in routine community care (Study 2).Method:A RCT compared the iCBT course (n=21) to a waitlist control (WLC, n=19) among participants diagnosed with PTSD. The iCBT group was followed up 3 months post-treatment. In Study 2, treatment outcomes were evaluated among 117 adults in routine community care. PTSD symptom severity was the primary outcome in both studies, with psychological distress and co-morbid anxiety and depressive symptoms providing secondary outcomes.Results:iCBT participants in both studies experienced significant reductions in PTSD symptom severity from pre- to post-treatment treatment (within-group Hedges’ g=.72–1.02), with RCT findings showing maintenance of gains at 3-month follow-up. The WLC group in the RCT also significantly improved, but Study 1 was under-powered and the medium between-group effect favouring iCBT did not reach significance (g=0.64; 95% CI, –0.10–1.38).Conclusions:This research provides preliminary support for the utility of iCBT for PTSD when provided with minimal clinician guidance. Future studies are needed to clarify the effect of differing levels of clinician support on PTSD iCBT outcomes, as well as exploring how best to integrate iCBT into large-scale, routine clinical care of PTSD.
Journal Article
Herd-level bovine tuberculosis risk factors: assessing the role of low-level badger population disturbance
2015
Bovine TB (bTB) is endemic in Irish cattle and has eluded eradication despite considerable expenditure, amid debate over the relative roles of badgers and cattle in disease transmission. Using a comprehensive dataset from Northern Ireland (>10,000 km
2
; 29,513 cattle herds), we investigated interactions between host populations in one of the first large-scale risk factor analyses for new herd breakdowns to combine data on both species. Cattle risk factors (movements, international imports, bTB history, neighbours with bTB) were more strongly associated with herd risk than area-level measures of badger social group density, habitat suitability or persecution (sett disturbance). Highest risks were in areas of high badger social group density
and
high rates of persecution, potentially representing both responsive persecution of badgers in high cattle risk areas and effects of persecution on cattle bTB risk through badger social group disruption. Average badger persecution was associated with reduced cattle bTB risk (compared with high persecution areas), so persecution may contribute towards sustaining bTB hotspots; findings with important implications for existing and planned disease control programmes.
Journal Article
Characteristics of Northern Irish cattle herds without bovine tuberculosis infection
by
Presho, Eleanor
,
Milne, Georgina
,
McCormick, Carl M
in
animal welfare
,
Animals
,
bovine tuberculosis
2019
BackgroundDespite ongoing eradication efforts, bovine tuberculosis (bTB) is endemic in cattle herds in Northern Ireland (NI). This disease has serious implications for the economy, farming and animal welfare. Previous research identified a population of herds which have remained free from bTB infection for 10 years (2004–2014). Understanding the characteristics of these herds may have important implications for eradication efforts, such as spatially targeted interventions.MethodsA cluster analysis and a retrospective case–control analysis was conducted to compare bTB- free herds with herds which experienced prolonged infection (ie, bTB breakdowns lasting more than ≥ 365 days).ResultsOnly small, localised clusters of herds which have remained free from bTB were revealed, thus limiting the potential for spatially targeted interventions. The results illustrated the importance of herd size to disease status; over 27 per cent of the bTB-free herds had up to 10 animals. However, the data also showed that there were no inward movements in the year before the bTB skin test in those herds which remained free from bTB.ConclusionsAttention should therefore be given to the cattle movement network in NI to better understand the risk associated with cattle purchasing.
Journal Article
The population and landscape genetics of the European badger (Meles meles) in Ireland
2018
The population genetic structure of free‐ranging species is expected to reflect landscape‐level effects. Quantifying the role of these factors and their relative contribution often has important implications for wildlife management. The population genetics of the European badger (Meles meles) have received considerable attention, not least because the species acts as a potential wildlife reservoir for bovine tuberculosis (bTB) in Britain and Ireland. Herein, we detail the most comprehensive population and landscape genetic study of the badger in Ireland to date—comprised of 454 Irish badger samples, genotyped at 14 microsatellite loci. Bayesian and multivariate clustering methods demonstrated continuous clinal variation across the island, with potentially distinct differentiation observed in Northern Ireland. Landscape genetic analyses identified geographic distance and elevation as the primary drivers of genetic differentiation, in keeping with badgers exhibiting high levels of philopatry. Other factors hypothesized to affect gene flow, including earth worm habitat suitability, land cover type, and the River Shannon, had little to no detectable effect. By providing a more accurate picture of badger population structure and the factors effecting it, these data can guide current efforts to manage the species in Ireland and to better understand its role in bTB. We present the results of a landscape and population genetics study on Irish badgers. We found overall clinal genetic variation across the island and influence of elevation and geographic distance on badger gene flow. Earthworm availability had a modest effect on gene flow. These results provide valuable information for management of the species.
Journal Article
Hui and Walter’s latent-class model extended to estimate diagnostic test properties from surveillance data: a latent model for latent data
by
Handel, Ian G.
,
Bronsvoort, B. Mark de Clare
,
McBride, Stewart H.
in
631/114/2415
,
692/699/255/1856
,
Animals
2015
Diagnostic test sensitivity and specificity are probabilistic estimates with far reaching implications for disease control, management and genetic studies. In the absence of ‘gold standard’ tests, traditional Bayesian latent class models may be used to assess diagnostic test accuracies through the comparison of two or more tests performed on the same groups of individuals. The aim of this study was to extend such models to estimate diagnostic test parameters and true cohort-specific prevalence, using disease surveillance data. The traditional Hui-Walter latent class methodology was extended to allow for features seen in such data, including (i) unrecorded data (i.e. data for a second test available only on a subset of the sampled population) and (ii) cohort-specific sensitivities and specificities. The model was applied with and without the modelling of conditional dependence between tests. The utility of the extended model was demonstrated through application to bovine tuberculosis surveillance data from Northern and the Republic of Ireland. Simulation coupled with re-sampling techniques, demonstrated that the extended model has good predictive power to estimate the diagnostic parameters and true herd-level prevalence from surveillance data. Our methodology can aid in the interpretation of disease surveillance data and the results can potentially refine disease control strategies.
Journal Article