November 2022
Nicola Harvey joins CVERA
We are delighted that Nicola Harvey has joined CVERA in her role as Veterinary Epidemiologist. Nicola completed her B.A. (Zoology) in TCD. Subsequently, she qualified from the University of Glasgow School of Veterinary Medicine and Surgery. In 2016, Nicola joined the Department of Agriculture, Food and the Marine (DAFM) as a Veterinary Inspector and was based in the Regional Veterinary Offices in Kerry and Limerick. Prior to joining DAFM, Nicola working for 16 years in mixed practice in the United Kingdom and in Co. Clare. As part of her MSc in Epidemiology at the London School of Tropical Medicine and Hygiene, Nicola will be researching the potential of Whole Genome Sequencing (WGS) and its use in bTB epidemiology.
A computer model for Johne’s disease in Ireland
A computer model for Johne’s disease in Ireland has now been developed, providing an in silico representation of the behaviour of this disease in Irish dairy herds. Models such as this can be very useful, providing a means to ask ‘what if’ questions to assist with programme decision-making. This work was funded by Irish Department of Agriculture, Food and the Marine, and will support the Irish Johne’s Control Programme, run by Animal Health Ireland. Floor Biemans completed this work in collaboration with colleagues in INRAE in France, Jamie Tratalos and Simon More from CVERA, Lawrence Gavey from Animal Health Ireland and George Ramsbottom from Teagasc. The work is presented in three published papers. The (opens in a new window)first paper describes the within-herd model, which captures the compact spring calving pattern that is a feature in many Irish herds. This is then extended in the (opens in a new window)second paper to a regional model, incorporating actual animal movements between Irish dairy farms. In the (opens in a new window)third paper, Biemans et al. focus on opportunities to control the spread of infection between herds through risk-based trading (based on the Johne’s herd indicator as currently used in the programme) and the impact of a range of possible control strategies within infected herds. Risk-based trading effectively reduced the increase in herd prevalence over a 10-year-period in Ireland; however, for risk-based trading to be effective, a high percentage of dairy herds had to participate. The most important within-herd measures were improved herd hygiene and early culling of highly infectious cows. Combining risk-based trading with within-herd measures reduced within-herd prevalence even more effectively.
Bovine tuberculosis in youngstock cattle: A narrative review
Like most infectious diseases, the risk of contracting and spreading bovine tuberculosis varies between ages. The aim of this narrative review was to summarize what is known about the susceptibility, diagnosis, transmission (infectiousness), and epidemiology to M. bovis in youngstock (up to 1-year of age). Youngstock are susceptible to M. bovis infection when exposed, with the capacity to develop typical bTB lesions. When recorded as positive by ante-mortem test, youngstock appear to have the highest probabilities of any age cohort for confirmation of infection post-mortem. They also appear to have the lowest false negative bTB detection risk. Mathematical models suggest that calves may also experience a lower force of infection (the rate that susceptible animals become infected). Policies to reduce testing for youngstock could lead to infected calves remaining undetected and increasing onwards transmission. Further studies are required to assess the risk associated with changes to testing policy for youngstock in terms of the impact for within-herd disease control, and how this may affect the transmission and persistence of infection across a network of linked herds. This study was led by Andrew Byrne in the DAFM One-Health and Welfare Scientific Support Unit in collaboration with colleagues from DAFM ERAD, UCD CVERA, Nancy Laboratory for Rabies and Wildlife (LRFSN) in France, and the UCD Tuberculosis Diagnostics and Immunology Research Laboratory. [(opens in a new window)Frontiers in Veterinary Science 9, 1000124 (2022)]
Quantification of local bovine tuberculosis (bTB) transmission in badgers and cattle with and without vaccination of badgers (Meles meles) in Ireland
Badger vaccination is progressively replacing culling as part of the Ireland's national strategy in controlling the spread of bTB. An understanding of the local dynamics of infection is key to ensuring the success of the vaccination programme. A test, vaccinate and removal or release field trial is ongoing to quantify local transmission of M. bovis in badgers and to evaluate the effects of local factors on badger vaccination. The field trial, consisting of 8 sweeps, is taking place at varies sites throughout Ireland. Seven sweeps are now complete, and the final sweep will commence early 2023. Preliminary observations indicate a wide range of, and interesting trends in, local vaccination coverages, field-test positivity rates, and badger population densities. The influence of these local variations on the transmission of M. bovis in the badger-cattle system will be explored. Furthermore, the trial is providing insight into the efficacy of badger vaccination on the dynamics of infection in the multi-host system, both spatially and temporally. The results of this trial will help to inform national policy in relation to the vaccination programme. This work is led by Ann Barber from Wageningen University in The Netherlands & CVERA in association with the Dept. of Agriculture, Food and the Marine and is the subject of her PhD.
Schedule 8 prescribing
In Ireland between 2008 and 2022, intramammary antimicrobial (AM) products could be prescribed by a veterinary practitioner under what was known as Schedule 8 (or remote) prescribing. Under this prescribing route, an annual herd visit was not required when criteria were met as outlined in Animal Remedies Regulation 2007 to 2017 (statutory instruments No. 7786/2007 and 558/2017). This study sought a clearer understanding of the role of milk purchasers in the prescribing and sale of intramammary AM products in Ireland during 2019 and 2020, whilst this Regulation was in force. Significant differences between milk purchasers were observed in the quality of milk, as measured through somatic cell count values, from supplying herds. In the context of intramammary AM prescribing, veterinary oversight under this Regulation was very limited, with a single Schedule 8 prescriber, on average, prescribing for 549.3 herds. The sale of intramammary AM products through milk purchasers represented 15.2% and 26.9% of national sales in in-lactation and dry cow tubes, respectively. There were also significant associations between EMA classification and route of sale (through milk purchasers or otherwise), both for in-lactation and dry cow tubes, reinforcing the need for Irish veterinary practitioners to move away from EMA category B intramammary AMs. Past experiences with Schedule 8 prescribing (no longer permitted from 28 January 2022) may influence current efforts towards improved intramammary AM stewardship. This study was led by Simon More in collaboration with colleagues from CVERA and the UCD School of Veterinary Medicine. [This paper will be available shortly in the (opens in a new window)Irish Veterinary Journal (in press)]
Understanding the dog population of the Republic of Ireland: insight from existing data sources?
Reliable information about national pet dog populations is an important contributor to informed decision-making, both by governments and national dog welfare organisations. In some countries, there is an improved understanding of aspects of the national pet dog population, but as yet limited published information is available in Ireland. This study highlights the challenges faced when using existing national data to gain insights into the dog population of Ireland. The linking of existing national databases (individual dog identification, dog licencing, dog control statistics) has the potential to improve both the representativeness and accuracy of information about the Irish pet dog population. In the next phases of our work, we focus on the work of dog welfare organisations, given both the increased role played by these organisations and the substantial public funding that has been committed in this sector. This study which is the first in a series of three was led by Simon More in collaboration with colleagues from CVERA, the School of Veterinary Medicine, Animal Health Ireland, and the Department of Agriculture, Food and the Marine. [(opens in a new window)Irish Veterinary Journal 75, 16 (2022)]
High accuracy monitoring of honey bee colony development by image analysis
Honey bees are key insect pollinators, providing important economic and ecological value for human beings and ecosystems. This has triggered the development of several monitoring methods for assessing the temporal development of colony size, food storage, brood and pathogens. In this study, we present and test a novel accurate and observer-independent method for honey bee colony assessment, capable of being fully standardized. Honey bee colony size is quantified by assessing the weight of adult bees, while brood and provision are assessed by taking photos and conducting image analysis of the combs with the image analysis software Deepbee®. We conclude that the use of this fully quantitative method offers a more accurate alternative to classic visual colony assessments, with negligible impact on colony development. This study was conducted by Nuno Capela from the Centre for Functional Ecology in Portugal in collaboration with colleagues from the Department of Ecoscience in Denmark, the European Food Safety Authority in Italy, the Evolution, Genome, Behavior and Ecology laboratory in France, eCentro de Investigac in Portugal, the Research Centre in Digitalization and Intelligent Robotics in Portugal, CVERA, and the Department of Agricultural, Forest, and Food Sciences in Italy. [(opens in a new window)Journal of Apicultural Research (in press)]
May 2022
Biennial Report 2020-2021
The Biennial Report 2020-21 outlines research conducted by, or in association with members of the Centre for Veterinary Epidemiology and Risk Analysis and the TB Diagnostics and Immunology Research Laboratory during 2020 & 2021. It also provides updates on ongoing projects. Areas of research include bovine tuberculosis, infectious diseases of cattle, other animal health and welfare issues, and COVID-19. This work is only possible in collaboration with colleagues from over 70 national and international organisations. The Biennial Report 2020/21, and previous versions of this report, are available at https://www.ucd.ie/cvera/reports/.
Risk factors for detection of bovine viral diarrhoea virus in low-risk herds during the latter stages of Ireland’s eradication programme
A national programme to eradicate bovine viral diarrhoea (BVD) has been in place in Ireland since 2013. An understanding of risks of infection in a low prevalence system is required to inform decision making in the end stages of eradication. This information would also support the development of post-eradication surveillance strategies. This paper describes the results of a case-control study in which cases were herds with one or more test positive calves for the first time in 2019 (n = 204). A range of risk factors were considered, and a generalised linear mixed model, including a county-level random effect, was developed. Our findings suggest that care with biosecurity at farm boundaries and visitors and equipment entering the farm, and avoidance or careful risk assessment of purchasing potentially pregnant animals, may help prevent introduction of BVDV to low-risk herds. At policy level, consideration of herd size, proximity to test positive herds and purchasing patterns of potentially pregnant cattle may help target surveillance measures towards the end of the eradication programme. [(opens in a new window)Casey-Bryars, M. et al - Preventive Veterinary Medicine 201, 105607]
Mastitis control and intramammary antimicrobial stewardship in Ireland: challenges and opportunities
The Veterinary Medicines Regulation (EU 2019/6) came into force in all EU member states on 28 January 2022, placing particular emphasis on prudent and responsible antimicrobial use in food animal production. The Regulation presents challenges to the Irish dairy industry, particularly with respect to current approaches to dry cow therapy. In response, the CellCheck technical working group (TWG, a technical group working in support of CellCheck, the national mastitis control programme) have developed pragmatic national and farm-level recommendations in support of improved mastitis control and intramammary antimicrobial stewardship in the Irish dairy industry. Periodic programme review will be needed, informed by ongoing monitoring of key performance indicators, to identify those actions that are most effective in an Irish context. [(opens in a new window)More, S.J. et al - Frontiers in Veterinary Science 9, 748353]
Intramammary antimicrobial sales in Ireland: a descriptive 2020 update
Intramammary (IM) antimicrobial sales data are currently the only feasible means to gain broad insights into on-farm usage of antimicrobials (AMs) relevant to mastitis control within the Irish dairy industry. Updating earlier work, this study describes sales data of intramammary antimicrobial usage in the Irish dairy industry in 2020. We observed a large increase in the use of dry cow (DC) IM AMs, from 0.95 to 1.13 defined course dose (DCDvet) per cow per year in 2019 and 2020 respectively, as well as evidence of ongoing usage of highest priority critically important AMs (HP CIAs). There was also a slight increase in lactation use of IM AMs, from 0.43 to 0.44 defined course dose (DCDvet) per cow per year. The sales pattern described here, most importantly the increased use of dry cow products and ongoing and increasing use of HP CIA products in both DC and lactation therapy raise concerns for the Irish dairy industry. This study was led by Catherine McAloon from the UCD School of Veterinary Medicine. [(opens in a new window)McAloon, C.I. et al - Irish Veterinary Journal 75, 5]
The Irish cattle population structured by enterprise type: overview, trade & trends
The cattle sector is the most important economic production unit of the Irish farming and agri-food sector. This paper presents an overview of the Irish cattle population structured by enterprise type. We collected data from the cattle register for the period 2015 to 2019 and assigned registered herds to one of 18 different herd types using a recently published herd type classification approach. It is now possible to explore temporal changes in enterprise (sub)types, and describe movements between these subtypes and from these subtypes to slaughter. This information will contribute to a number of future comparative studies, including cross-sectoral assessments of profitability, estimation of the extent of animal health losses on Irish cattle farms or structural analysis of Greenhouse Gas (GHG) emissions across production systems. This project was led by Jonas Brock from the Helmholtz Centre for Environmental Research GmbH - UFZ in Leipzig and Animal Health Ireland. [(opens in a new window)Brock, J. et al - Irish Veterinary Journal 75, 6]
Output-based assessment of herd-level freedom from infection in endemic situations: Application of a Bayesian Hidden Markov model
In the context of control programmes (CP) for cattle diseases, practical methods are needed to assess the confidence of freedom from infection that is achieved. As part of the STOC free project, a Bayesian Hidden Markov model was developed, called STOC free model, to estimate the probability of infection at herd-level. Using field data from control programmes for bovine viral diarrhoea virus (BVDV) in four study regions, this study sought to estimate the probability of herd-level freedom from BVDV in regions that are not (yet) free. The STOC free model calculates a posterior value for the model parameters (e.g. herd-level test sensitivity and specificity, probability of introduction of infection) and a predicted probability of infection. In all study regions, the predicted probabilities of freedom were very high, ranging from 0.98 to 1.00. Compared with scenario tree modelling, the STOC free model uses actual CP data and estimates are easily updated when new data becomes available. This project was led by Annika van Roon from Utrecht University. [(opens in a new window)van Roon, A.M. et al - Preventive Veterinary Medicine 204, 105662]
Development of a syndromic surveillance system for Irish dairy cattle using milk recording data
Emerging vector-borne diseases have become a substantial threat to cattle across Europe. Early detection is important, but difficult when clinical signs are non-specific. Furthermore, there is often a delay in the development of new diagnostic tests for novel pathogens which limits the ability to detect emerging disease in the initial stages. Syndromic Surveillance could potentially augment traditional methods by detecting aberrations in non-specific disease indicators. The aim of this study was to develop a syndromic surveillance system for Irish dairy herds based on routinely collected milk recording and meteorological data. We sought to determine whether the system would have detected the 2012 Schmallenberg virus (SBV) incursion into Ireland earlier than conventional surveillance methods. Using a range of thresholds, our model generated alarms throughout September 2012, between 4 and 6 weeks prior to the first laboratory confirmation of SBV in Ireland. This system for monitoring milk yield represents both a potentially useful tool for early detection of disease, and a valuable foundation for developing similar tools using other metrics. This project was led by Alexander Douglass from the UCD School of Veterinary Medicine. [(opens in a new window)Douglass, A.P. et al - Preventive Veterinary Medicine (in press)]
Simulating partial vaccine protection: BCG in badgers
In wildlife disease management, there are few diseases for which vaccination is a viable option. The human vaccine BCG has been used for the control of bovine tuberculosis in badgers since 2010 and is expected to increase. Understanding the long-term effects of repeated vaccination campaigns on disease prevalence is vital, but modelling thus far has generally assumed that a vaccine provides perfect protection to a proportion of the population, and that animals exposed to a repeated vaccination have a second independent chance of becoming protected. We held a workshop with experts in the field to obtain consensus over the main pathways for partial protection in the badger, and then simulated these using an established model. The available data supported the possibility that some individuals receive no benefit from the BCG vaccine, others may result in a delayed disease progression and in the remaining animals, vaccine protected the individual from any onward transmission. Simulating these pathways using different levels of overall efficacy demonstrated that partial protection leads to a reduced effect of vaccination, but in all of the identified scenarios it was still possible to eradicate disease in an isolated population with no disease introduction. This project was led by Graham Smith from APHA. [(opens in a new window)Smith, G.C. et al - Preventive Veterinary Medicine 204, 105635]
Rapid antigen testing for SARS-CoV-2 infection in a university setting in Ireland: learning from a 6-week pilot study
With the ongoing circulation of SARS-CoV-2 in countries across the world it is essential to identify effective ways to reduce the risk of infection while allowing society to function as close to ‘normal’ as possible. Serial testing using rapid lateral flow antigen tests is a possible way to do this by screening populations in a targeted way, identifying infectious (both symptomatic and asymptomatic) people and removing them from circulation while infectious. This study evaluated a testing programme that was introduced into a university setting, assessing some of the factors that impact participation in such a study among both staff and students. Overall, almost all respondents to the survey stated that they were happy with having a testing programme present in the workplace and it helped to reduce anxiety associated with COVID-19. There were differing levels of participation among staff and students, for reasons that are discussed. Different motivations drive participation in different cohorts and different messaging/incentivisation is needed to encourage participation in those different cohorts. This project was led by Gerald Barry from the UCD School of Veterinary Medicine. [(opens in a new window)Barry, G. et al - Public Health in Practice 3, 100255]
Potential application of SARS-CoV-2 rapid antigen diagnostic tests for the detection of infectious individuals attending mass gatherings – a simulation study
Rapid Antigen Diagnostic Tests (RADTs) for the detection of SARS-CoV-2 offer advantages in that they are cheaper and faster than currently used PCR tests but have reduced sensitivity and specificity. One potential application of RADTs is to facilitate gatherings of individuals, through testing of attendees at the point of, or immediately prior to entry at a venue. Understanding the baseline risk in the tested population is of particular importance when evaluating the utility of applying diagnostic tests for screening purposes. Using incidence data from Ireland, we developed scenarios to estimate the prevalence of infectious attendees, then simulated the likely number of positive and negative test results, the proportion of cases detected and the corresponding positive and negative predictive values, and the cost per case identified. Our findings suggest that for each reported case on a given day, there are likely to be 13.8 additional infectious individuals also present in the community. Prevalence ranged from 0.26% for “mostly older” events in July-August, to 2.6% for “mostly younger” events in January. For large events (10,000 attendees) the expected number of infectious attendees ranged from 27 (95% confidence intervals 12 to 45) for mostly older events in July-August, to 267 (95% confidence intervals 134 to 436) infectious attendees for mostly younger attendees in January. Given rapid changes in SARS-CoV-2 incidence over time, we developed an RShiny app to allow users to run updated simulations for specific events. This project was led by Conor McAloon from the UCD School of Veterinary Medicine. [(opens in a new window)McAloon, C.G. et al - Frontiers in Epidemiology 2, 862826]
M. bovis 2022
The Seventh International conference on Mycobacterium bovis is taking place in Galway from 7-10 June 2022. To view the programme or to register for the conference, please visit (opens in a new window)https://www.mbovis2022.com/
February 2022
The new Veterinary Medicines Regulation: rising to the challenge
This article by More et al focuses on the new Veterinary Medicines Regulation, which is applicable across all Member States of the European Union, including Ireland, from 28 January 2022. From this date, prophylactic use of antimicrobials (AMs) in groups of animals is banned, metaphylactic use in groups of animals is restricted, and certain AMs are reserved for humans only. For private veterinary practitioners (PVPs), the Regulation will lead to specific prescribing changes, including the requirement to shift from blanket to selective dry cow therapy and for prescribing choices to be guided by the categorisation for AMs developed by the European Medicines Agency (EMA). More broadly, the Regulation requires a fundamental shift in thinking both in terms of AM usage and of the role of the PVP. Given the close association between mastitis control and intramammary AM stewardship, it is imperative that prescribing and mastitis control decisions are made concurrently. On those farms with sub-optimal mastitis control, mastitis issues will need to be sustainably resolved. A detailed farm investigation by the PVP, in partnership with the farmer and other milk quality professionals, is essential, to understand the epidemiology and on-farm drivers of mastitis, to develop farm-specific action plans, and to facilitate ongoing monitoring of progress. It is vital that PVPs provide leadership, with the provision of a holistic, herd health approach to inform both prescribing and mastitis control decisions in herds under their care. The study was conducted by members of the UCD School of Veterinary Medicine, Animal Health Ireland and UCD CVERA. [(opens in a new window)Irish Veterinary Journal 75, 2 (2022)].
Future risk assessment of M. bovis in raw cheese milk
Specialty cheeses, which are often produced using raw milk, present challenges to risk managers in countries where Mycobacterium bovis is endemic or (re-) emerging. A key concern is the potential risk of zoonotic transmission of M. bovis via the consumption of dairy products produced using raw milk originating from herds infected with M. bovis (bovine tuberculosis, bTB). Two studies by Collins et al have now been published in support of future risk assessment of M. bovis in raw cheese milk:
Prevalence of Mycobacterium bovis in milk on dairy cattle farms: an international systematic literature review and meta-analysis
This study systematically reviewed published studies to estimate the prevalence of M. bovis in on-farm bulk-tank milk (BTM) and individual cow's milk (IM) by meta-analysis. For IM, the overall prevalence was summarised at 5% (95%CI: 3%–7%). In TST positive cows, prevalence was summarised at 8% (95%CI: 4%–13%). For BTM, the overall prevalence independent of individual herd TST infection status was summarised at 5% (95%CI: 0%–21%). There was considerable heterogeneity evident among the included studies, while PIs were also wide. Despite international efforts to control tuberculosis, this study by Collins et al highlights the risk of zoonotic transmission of M. bovis via unpasteurised milk and dairy products made using raw milk. [(opens in a new window)Tuberculosis 132, 102166 (2022)].
Parameter estimates to support future risk assessment of Mycobacterium bovis in raw milk cheese
The aim of this study was to determine parameter estimates to support the future risk assessment of Mycobacterium bovis in raw milk cheese. In this study, the hazard was identified as viable M. bovis organisms in raw milk cheese. Parameters of interest in this study related to exposure assessment (the estimated extent of human exposure to viable M. bovis organisms) and hazard characterisation (the risk posed to human health following exposure to viable M. bovis organisms). The pathway for exposure assessment was visualised using a conceptual framework, which describes the steps through which M. bovis may be transferred from an infected animal(s) through manufacturing to the final cheese product. Estimation of most parameters for exposure assessment and hazard characterisation was undertaken using systematic literature review and meta-analysis. Estimates could be derived for many parameters, but not all. In particular, the number of M. bovis organisms excreted in the milk and present in the faeces of infected cattle are unknown. There is zero-tolerance for M. bovis in foods of animal origin destined for human consumption in European legislation. [(opens in a new window)Microbial Risk Analysis (in press) (2022)].
Is there an association between road building and bovine tuberculosis herd risk? A three time-points study in Ireland, 2011-2020
In this study, we investigated whether (motorway) road construction was associated with an increased risk of bTB in associated cattle herds. For this study, we considered three observation periods relating to road building, including pre-construction (2011–2014), construction (2015–2017) and post-construction (2018–2019). Herds located at a distance of >3 km from the roadworks were found to be at reduced risk of a bTB breakdown over the construction period compared with those situated within 1 km of the roadworks for ≥1 reactor/s (>3 km and construction vs. <1 km: OR: 0.595, 95 % Confidence Interval (CI): 0.354−0.999) or ≥3 reactors (>3 km and construction vs. <1 km: OR: 0.431, 95 % CI: 0.174–1.067). Other previously reported risk factors such as inward movements, herd-size and herd-type were also associated with bTB risk in the final models (≥1 reactor/s and ≥3 reactors). These findings by Barroso et al appear to be consistent with bTB breakdowns being a consequence as opposed to coincident to road construction, given the temporal and spatial consistency of the evidence. Further research is warranted to verify this pattern occurs elsewhere, and the underlying biological mechanism. Until further data are available, we recommend that badgers are vaccinated, as a precautionary measure, in advance of the commencement of major roadworks. The study was conducted by members of the Instituto de Investigación en Recursos Cinegéticos (UCLM-CSIC) in Spain, the DAFM Ruminant Animal Health Division, the DAFM One Health Scientific Support Unit & UCD CVERA. [(opens in a new window)Preventive Veterinary Medicine 198, 105542 (2022)].
Numbers of close contacts of individuals infected with SARS-CoV-2 and their association with government intervention strategies
Contact tracing is conducted with the primary purpose of interrupting transmission from individuals who are likely to be infectious to others. Secondary analyses of data on the numbers of close contacts of confirmed cases could also provide an early signal of increases in contact patterns that might precede larger than expected case numbers; evaluate the impact of government interventions on the number of contacts of confirmed cases; or provide data information on contact rates between age cohorts for the purpose of epidemiological modelling. We analysed data from 140,204 close contacts of 39,861 cases in Ireland from 1st May to 1st December 2020. Negative binomial regression models highlighted greater numbers of contacts within specific population demographics, after correcting for temporal associations. Separate segmented regression models of the number of cases over time and the average number of contacts per case indicated that a breakpoint indicating a rapid decrease in the number of contacts per case in October 2020 preceded a breakpoint indicating a reduction in the number of cases by 11 days. We found that the number of contacts per infected case was overdispersed, the mean varied considerable over time and was temporally associated with government interventions. Analysis of the reported number of contacts per individual in contact tracing data may be a useful early indicator of changes in behaviour in response to, or indeed despite, government restrictions. This study, led by McAloon et al, provides useful information for triangulating assumptions regarding the contact mixing rates between different age cohorts for epidemiological modelling. [(opens in a new window)BMC Public Health 21, 2238 (2021)].
Seroprevalence of Mycoplasma bovis in bulk milk samples in Irish dairy herds and risk factors associated with herd infection status
This study by McAloon et al is the first to describe herd apparent prevalence for Mycoplasma bovis exposure in Irish dairy herds. There is high herd apparent prevalence among dairy herds in Ireland, with evidence from 45% of tested herds of at least past exposure to M. bovis. Risk factors associated with herd-level seropositivity included increasing herd size, the number of contiguous neighbouring farms, the buying in behaviour (reflected as an increased risk associated with those herds who bought from more than 2 sources) and region (as identified by county). [(opens in a new window)Journal of Dairy Science (in press) (2022)].
Freedom from infection studies
Freedom from infection is an important concept underpinning the safe trade of cattle. However, control programmes (CPs) can vary between countries, and it can be difficult to compare freedom claims under different programmes. An EU project, STOC free, has been considering this issue in detail, evaluating methods that could be used to allow these comparisons. Two studies in support this work were recently published by Mercat et al and by Madouasse et al:
Capacity of a Bayesian model to detect infected herds using disease dynamics and risk factor information from surveillance programmes: A simulation study
Our objective was to evaluate the capacity of a Bayesian Hidden Markov Model, which computes a herd-level probability of being infected, to detect infected herds compared to using test results only. Herd-level risk factors, infection dynamics and associated test results were simulated in a population of herds, for a wide range of realistic infection contexts and test characteristics. The model was used to predict the infection status of each herd from longitudinal data: a simulated risk factor and a simulated test result. The model predictive performances were evaluated using the simulated herd status as the gold standard. The model detected more infected herds than a single final test in 85 % of the scenarios which converged. The proportion of infected herds additionally detected by the model, compared to test results alone, varied depending on the context. It was higher in a context of a low herd test sensitivity. On average, around 20 %, for high test sensitivity scenarios, and 40 %, for low test sensitivity scenarios, of infected herds that were undetected by the test were accurately classified as infected by the model. Detection of additional newly infected herds was always associated with an increased number of false positive herds (except for one scenario). The number of false positive herds was lower for scenarios with low herd test sensitivity and moderate to high incidence and prevalence. These results by Mercat et al highlight the benefit of the model, in particular for control programmes with infection present at an endemic level in a population and reliance on test(s) of low sensitivity. [(opens in a new window)Preventive Veterinary Medicine 200, 105582 (2022)].
A modelling framework for the prediction of the herd-level probability of infection from longitudinal data
In this paper, we describe a statistical model for the prediction of herd-level probabilities of infection from longitudinal data collected as part of CPs against infectious diseases of cattle. The model was applied to data collected as part of a CP against bovine viral diarrhoea virus (BVDV) infection in Loire-Atlantique, France. The model represents infection as a herd latent status with a monthly dynamics. This latent status determines test results through test sensitivity and test specificity. The probability of becoming status positive between consecutive months is modelled as a function of risk factors (when available) using logistic regression. Modelling is performed in a Bayesian framework. Prior distributions need to be provided for the sensitivities and specificities of the different tests used, for the probability of remaining status positive between months as well as for the probability of becoming positive between months. The impact of using different prior distributions and model implementations on parameter estimation was evaluated. The main advantage of this model is its ability to predict a probability of being status positive in a month from inputs that can vary in terms of nature of test, frequency of testing and risk factor availability/presence. The main challenge in applying the model to the BVDV CP data was in identifying prior distributions, especially for test characteristics, that corresponded to the latent status of interest, i.e. herds with at least one persistently infected (PI) animal. The model is available on Github as an R package ((opens in a new window)https://github.com/AurMad/STOCfree) and can be used to carry out output-based evaluation of disease CPs. The study was conducted by Madouasse et al. [(opens in a new window)Peer Community Journal 2, e4 (2022)].
M. bovis 2022
The Seventh International Conference on Mycobacterium bovis (M. bovis 2022) will take place in Galway from 7-10 June 2022. The conference was originally due to take place in 2020. The Committee would like to thank our speakers, delegates, organisers, and sponsors for their continued support of the conference. The conference has attracted a high number of delegates from a wide range of countries. Building on the success of Cardiff 2014, M. bovis 2022 will gather together scientists, policy makers, veterinarians and industry stakeholders from around the world with the aim of identifying constraints and providing practical solutions for the control and eradication of the M. bovis. To maintain the health and safety of all involved, the conference will abide by all public health measures applicable at the time of the conference. We would ask that all those intending to come to M. bovis 2022 familiarise themselves with travel and public health measures that are in place. The M. bovis 2022 Organising Committee will continue to monitor the situation in Ireland and tailor our plans accordingly for a safe in-person conference in June 2022. Please visit (opens in a new window)www.mbovis2022.com for more information.