More, Simon John
More, Simon John
More, Simon John
Now showing 1 - 10 of 169
- PublicationThe use of monoclonal antibody-based ELISAs to monitor chemotherapeutic effects in the bovine-Onchocerca gibsoni drug screenThree monoclonal antibodies directed towards antigens of Onchocerca gibsoni were used in antigen detection ELISAs to detect parasite antigens in sera from 100 cattle infected with O. gibsoni, in trials with the filaricidal compounds CGP 6140, CGP 20309, CGP 20376, CGP 21833, CGP 24589 and CGP 26702. Measurable levels of parasite antigens were highly variable, both within and between treatment and control groups of animals, with no consistent trends which related to time after treatment, micro or macrofilaricidal effects against O. gibsoni, or dose rate for any of the compounds used. It was concluded that these assays were unsuitable as a method of identifying drug-induced damage to O. gibsoni following the administration of these compounds. A detailed protocol for selecting suitable assays is discussed.
- PublicationShaping our future: animal health in a global trading environment(Springer (Biomed Central Ltd.), 2007)Irish farming is facing a period of unprecedented change, in large part due to the increasing globalisation of agriculture. The challenges to Irish farming are substantial, given ongoing reductions in farm-gate returns to Irish farmers, as a consequence of increasing international competition, decreasing levels of subsidy support as a result of international (WTO) and EU-level decisions and a rapid increase in the relative cost of production of Irish product.
- PublicationDilemmas experienced by government veterinarians when responding professionally to farm animal welfare incidents in IrelandObjectives: This paper identifies the dilemmas experienced by government veterinarians during their investigations of farm animal welfare incidents that involve herd owner social, health, and/or psychological difficulties. The paper builds on exploratory qualitative research into the impact of these difficulties on farm animal welfare.Design: The study used a qualitative research approach. Focus groups were conducted.Setting: In Ireland, an Early Warning System (EWS), which brings together relevant agencies, is in place to identify and prevent farm animal welfare problems before they become critical. This study is concerned with the experiences of government veterinarians who respond to farm animal welfare incidents. Specific focus is on incidents that involve herd owner social/ psychological/health-related difficulties.Participants: In total, n=18 government veterinarians (representing 15 per cent of the population sample), all with a keen interest in farm animal welfare, participated. These were selected on the basis of their interest, experience, and involvement in farm animal welfare. One government veterinarian declined to participate. Four focus groups were conducted with government veterinarians. These took place in the south (S), south-west (SW), midlands (M), and north-west region of Ireland (NW). All 16 District Veterinary Offices (DVOs) were represented in the focus groups.Results: The results reveal three professional dilemmas that exist for government veterinarians: (1) defining professional parameters; (2) determining the appropriate response; (3) involvement versus detachment. Participants reported not wanting any additional training. Instead, it was agreed that a formal bridge to social service providers who have the professional capability to respond appropriately and with confidence, was required.Conclusions: Clearly defined guidelines are required for government veterinarians in their encounters with farm animal welfare incidents where there is a complex human component. A coordinated multiagency approach that is flexible enough to meet the needs of individual farm animal welfare cases is required.
- PublicationA modelling framework for the prediction of the herd-level probability of infection from longitudinal datahe collective control programmes (CPs) that exist for many infectious diseases of farm animals rely on the application of diagnostic testing at regular time intervals for the identification of infected animals or herds. The diversity of these CPs complicates the trade of animals between regions or countries because the definition of freedom from infection differs from one CP to another. 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, using either Stan or JAGS. 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. When risk factors are available, prior distributions need to be provided for the coefficients of the logistic regression, replacing the prior for the probability of becoming positive. From these prior distributions and from the longitudinal data, the model returns posterior probability distributions for being status positive for all herds on the current month. Data from the previous months are used for parameter estimation. 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 (https://github.com/AurMad/STOCfree) and can be used to carry out output-based evaluation of disease CPs.
- PublicationCOVID-19 epidemiological parameters summary documentIn response to the coronavirus (COVID-19) outbreak, the Irish Epidemiological Modelling Advisory Group (IEMAG) for COVID-19 was established to assist the Irish National Public Health Emergency Team (NPHET) in their decision-making during the pandemic. A subcommittee from IEMAG (the epidemiological parameters team) was tasked with researching the various parameters, leading to the development of a series of synthesis documents relevant to the parameterisation of a COVID-19 transmission model for Ireland. These parameters include: • R0/R • Latent period & relative importance of pre-symptomatic period • Incubation period • Generation time & serial interval • Proportion of infected who are asymptomatic, by age • Length of infectious period in asymptomatic people and in symptomatic people who do not isolate • Time from onset of symptoms to diagnosis/test results and to hospitalisation • Length of hospital stay and admission to ICUs • Relative infectiousness of asymptomatic versus symptomatic infected people. The current document presents an up-to-date summary of these synthesis documents. A further synthesis document on age-related susceptibility and age-related infectiousness is in preparation.
- PublicationPotential Application of SARS-CoV-2 Rapid Antigen Diagnostic Tests for the Detection of Infectious Individuals Attending Mass Gatherings – A Simulation StudyRapid 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. We used incidence data from January and from July-August 2021, periods of relatively high and low levels of infection, to estimate the prevalence of infectious individuals in the community at particular time points and simulated mass gatherings by sampling froma series of age cohorts. Nine different illustrative scenarios were simulated, small (n = 100), medium (n = 1,000) and large (n = 10,000) gatherings each with 3 possible age constructs: mostly younger, mostly older or a gathering with equal numbers from each age cohort. For each scenario, we estimated 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 small events (100 attendees) the expected number of infectious attendees ranged from <1 across all age constructs of attendees 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.
- PublicationSome Perceptions of Footrot Eradication in North-Western New-South Wales(University of New South Wales, 1993-01-01)The Footrot Strategic Plan (FSP) aims to progressively eradicate non-benign footrot in sheep from New South Wales. All but a small portion of the drier regions of NSW is now gazetted with Protected Area status - placing legal requirements on farmers and relevant authorities in relation to disease notification and, where disease exists, farm quarantine and disease eradication. The author's experience from north western NSW suggests, however, that despite these legal requirements, many local producers would be unlikely to notify upon suspecting disease. Furthermore, of those producers with properties quarantined for footrot during the period 1990-1992 in the Coonamble Rural Lands Protection Board, almost half lacked a real commitment to footrot eradication.Research towards improving the FSP and related programs has been dominated by methods to overcome technical obstacles. In non-endemic regions of NSW, such as the north west, however, major constraints on the FSP include problems of an economic or social nature. This paper discusses some constraints limiting the acceptance and adoption of the FSP in the Coonamble region of NSW and identifies some possible solutions to these problems.
- PublicationLessons learned during the successful eradication of bovine tuberculosis from AustraliaThere are very few international examples of the successful eradication of bovine tuberculosis (TB, caused by infection with Mycobacterium bovis) from a national cattle population. This paper presents a brief overview of the successful TB eradication programme in Australia from 1970, with primary emphasis on lessons of international relevance that were learned from the Australian experience. The national brucellosis and tuberculosis eradication campaign ran for 27 years from 1970 to 1997 and has been followed by ongoing abattoir surveillance. Rapid progress towards eradication was made in southern Australia, but proved much more challenging in extensive pastoral areas of northern Australia. Declaration of TB freedom was made on December 31, 1997. A range of factors were critical to this success, including a compelling rationale for eradication, an agreed final outcome, industry commitment and financial support, a business model for programme planning, implementation and review, consistent and transparent technical standards underpinned by a strict regulatory regime and applied research, the critical role of abattoir surveillance, effective elimination of residual infection and objective measures of programme progress. Although direct translation of some of these experiences may not be possible, many of the lessons learned from the Australian experience may be relevant to other countries.
Scopus© Citations 63 559
- PublicationModelling transmission and control of Mycobacterium avium subspecies paratuberculosis within Irish dairy herds with compact spring calvingParatuberculosis is a chronic bacterial infection of the intestine in cattle caused by Mycobacterium avium subspecies paratuberculosis (Map). To better understand Map transmission in Irish dairy herds, we adapted the French stochastic individual-based epidemiological simulation model to account for seasonal herd demographics. We investigated the probability of Map persistence over time, the within-herd prevalence over time, and the relative importance of transmission pathways, and assessed the relative effectiveness of test-and-cull control strategies. We investigated the impact on model outputs of calf separation from cows (calves grazed on pasture adjacent to cows vs. were completely separated from cows) and test-and-cull. Test-and-cull scenarios consisted of highly test-positive cows culled within 13 or 4 weeks after detection, and calf born to highly test-positive cows kept vs removed. We simulated a typical Irish dairy herd with on average 82 lactating cows, 112 animals in total. Each scenario was iterated 1000 times to adjust variation caused by stochasticity. Map was introduced in the fully naive herd through the purchase of a moderately infectious primiparous cow. Infection was considered to persist when at least one infected animal remained in the herd or when Map was present in the environment. The probability of Map persistence 15 years after introduction ranged between 32.2–42.7 % when calves and cows had contact on pasture, and between 18.9–29.4 % when calves and cows were separated on pasture. The most effective control strategy was to cull highly test-positive cows within four weeks of detection (absolute 10 % lower persistence compared to scenarios without control). Removing the offspring of highly test-positive dams did not affect either Map persistence or within-herd prevalence of Map. Mean prevalence 15 years after Map introduction was highest (63.5 %) when calves and cows had contact on pasture. Mean prevalence was 15 % lower (absolute decrease) when cows were culled within 13 weeks of a high test-positive result, and 28 % lower when culled within 4 weeks. Around calving, the infection rate was high, with calves being infected in utero or via the general indoor environment (most important transmission routes). For the remainder of the year, the incidence rate was relatively low with most calves being infected on pasture when in contact with cows. Testing and culling was an effective control strategy when it was used prior to the calving period to minimize the number of highly infectious cows present when calves were born.
Scopus© Citations 7 222