Dataset Information

Post-mortem surveillance of bovine tuberculosis in Ireland: herd-level variation in the probability of herds disclosed with lesions at routine slaughter to have skin test reactors at follow-up test.

ABSTRACT: Post-mortem surveillance in Ireland discloses skin-test negative cattle with presumptive evidence of infection of Mycobacterium bovis (lesions at routine slaughter (LRS)), the causative agent of bovine tuberculosis (bTB). Laboratory confirmation of lesions has impacts on trade restrictions for herds, therefore if laboratory capacity was diminished, how herds are treated would require an informed risk policy. Here we report the proportion of herds with subsequent evidence of within-herd transmission, based on skin-test results. We assess how herd-size, herd-type, and bTB-history affect the probability of additional reactors at follow-up test using univariable and multivariable random-effects models. The study represents a rapid response to developing an evidential base for policy demands during an extraordinary event, the COVID-19 epidemic in Ireland. A dataset from 2005 to 2019 of breakdowns were collated. Overall, 20,116 breakdowns were initiated by LRS cases. During the index tests of these breakdowns, 3931 revealed ?1 skin-test reactor animals (19.54%; ?1 standard reactors: 3827; 19.02%). Increasing herd-size was associated with reactor disclosure on follow-up. For small herds (<33 animals), 11.74% of follow-up tests disclosed ?1 reactor; 24.63% of follow-up tests from very large herds (>137) disclosed ?1 reactors. Beef (13.87%) and "other" (13%) herd production types had lower proportion of index tests with reactors in comparison with dairy (28.27%) or suckler (20.48%) herds. Historic breakdown size during the previous 3-years was associated reactor disclosure risk on follow-up. Our results are useful for rapid tailored policy development aimed at identifying higher risk herds.

SUBMITTER: Byrne AW

PROVIDER: S-EPMC7312117 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Post-mortem surveillance of bovine tuberculosis in Ireland: herd-level variation in the probability of herds disclosed with lesions at routine slaughter to have skin test reactors at follow-up test.

Byrne Andrew W AW Barrett Damien D Breslin Philip P Madden Jamie M JM O'Keeffe James J Ryan Eoin E

Veterinary research communications 20200624 3-4

Post-mortem surveillance in Ireland discloses skin-test negative cattle with presumptive evidence of infection of Mycobacterium bovis (lesions at routine slaughter (LRS)), the causative agent of bovine tuberculosis (bTB). Laboratory confirmation of lesions has impacts on trade restrictions for herds, therefore if laboratory capacity was diminished, how herds are treated would require an informed risk policy. Here we report the proportion of herds with subsequent evidence of within-herd transmiss ...[more]

PMID: 32583301

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Project description:Bovine tuberculosis (TB) is an important animal health issue in many parts of the world. In England and Wales, the primary test to detect infected animals is the single intradermal comparative cervical tuberculin test, which compares immunological responses to bovine and avian tuberculins. Inconclusive test reactors (IRs) are animals that demonstrate a positive reaction to the bovine tuberculin only marginally greater than the avian reaction, so are not classified as reactors and immediately removed. In the absence of reactors in the herd, IRs are isolated, placed under movement restrictions and re-tested after 60 days. Other animals in these herds at the time of the IR result are not usually subject to movement restrictions. This could affect efforts to control TB if undetected infected cattle move out of those herds before the next TB test. To improve our understanding of the importance of IRs, this study aimed to assess whether median survival time and the hazard of a subsequent TB incident differs in herds with only IRs detected compared with negative-testing herds. Survival analysis and extended Cox regression were used, with herds entering the study on the date of the first whole herd test in 2012. An additional analysis was performed using an alternative entry date to try to remove the impact of IR retesting and is presented in the Supplementary Material. Survival analysis showed that the median survival time among IR only herds was half that observed for clear herds (2.1 years and 4.2 years respectively; p < 0.001). Extended Cox regression analysis showed that IR-only herds had 2.7 times the hazard of a subsequent incident compared with negative-testing herds in year one (hazard ratio: 2.69; 95% CI: 2.54, 2.84; p < 0.001), and that this difference in the hazard reduced by 63% per year. After 2.7 years the difference had disappeared. The supplementary analysis supported these findings showing that IR only herds still had a greater hazard of a subsequent incident after the IR re-test, but that the effect was reduced. This emphasizes the importance of careful decision making around the management of IR animals and indicates that re-testing alone may not be sufficient to reduce the risk posed by IR only herds in England and Wales.

Project description:Veterinarians are faced with significant conflicts of interest when issuing certificates for the transport and slaughter of acutely injured and casualty livestock. In a recent Policy Delphi study, emergency and casualty slaughter certification was a key concern identified by veterinary professionals in Ireland. In this case study (the third in a series of three resulting from a research workshop exploring challenges facing the veterinary profession in Ireland; the other two case studies investigate clinical veterinary services and the on-farm use of veterinary antimicrobials), we aim to provide a value-based reflection on the constraints and opportunities for best practice in emergency and casualty slaughter certification in Ireland.Using a qualitative focus group approach, this study gathered evidence from relevant stakeholders, namely a representative from the regulatory body, local authority veterinarians with research experience in emergency slaughter, an animal welfare research scientist, official veterinarians from the competent authority, a private veterinary practitioner, and a member of a farming organisation. Results revealed a conflict between the responsibility of private veterinary practitioners (PVPs) to safeguard the welfare of acutely injured bovines on-farm and the client's commercial concerns. As a consequence, some PVPs may feel under pressure to certify, for example, an acutely injured animal for casualty slaughter instead of recommending either on-farm emergency slaughter or disposal by the knackery service. Among Official Veterinarians, there are concerns about the pressure within processing plants to accept acutely injured livestock as casualty animals. Confusion pertaining to legislation and definition of fitness to travel also contribute to these dilemmas.Conflicts of interest arise due to the gap between governance and provision to facilitate on-farm emergency slaughter of livestock. Increased availability and acceptance of on-farm emergency slaughter by Food Business Operators (FBOs) would mitigate the need to certify acutely injured animals fit for transport and slaughter and thereby safeguard animal welfare. In the absence of nationwide availability and acceptance of on-farm emergency slaughter by FBOs, consideration should be given to methods to encourage all those involved in the food chain to prioritise animal welfare when in conflict with the commercial value of the animal. Training and guidelines for PVPs on the regulatory landscape and ethical decision-making should become available. The reintroduction of the fallen animal scheme should be considered to support farm animal welfare.

Project description:Dairy systems require that each cow calves annually to have an efficient milk production cycle. In systems where milk production is maximized, the male offspring from dairy breed sires tend to have poor beef production traits and, therefore, can be of low economic value. Few studies have been published on the factors impacting early slaughtering of calves in peer-reviewed literature. Here we present an analysis of national data on calves slaughtered from 2018 to 2022 in Ireland. Data (Jan 2018-May 2022) on all cattle <6 months of age were collated at a national level and were described at calf-, herd-, and county-levels. These data were statistically analyzed at per-capita slaughter rates (calves/calf born) using negative binomial regression models with an offset. There were 125,260 calves slaughtered early (1.09% of total births) recorded in the dataset from 1,364 birth herds during the study period, of which 94.8% (118,761) were male. 51.7% were classified as Friesian-cross (FRX), 11.5% Friesian (FR) and 32.1% Jersey-cross (JEX). The median age at slaughter was 16 days (Mean: 18.9 days; IQR: 13–22). The median calves/herd slaughtered was 16 (mean: 91.8); median calves/herd/year slaughtered was 21 (mean: 42.0). There was substantial variation in counts of calves slaughtered across herds, years, and counties. Herd calf slaughter rates and per capita calf slaughter rates increased significantly in 2022, with the highest rates over the time series. Calf slaughter rates varied significantly with herd size, year, and major breed (Jersey; JE). Herds which were more recently established tended to have higher calf slaughter rates. Herds that repeatedly slaughtered calves over 2 or more years tended to be larger and slaughtered more calves/herd/year. The slaughtering of calves is not widespread across the dairy industry in Ireland. The distribution of calves slaughtered per herd demonstrate that a small number of herds contributed disproportionately to calf slaughter numbers. Such herds tended to be very large (herd size), more recently established (2016 onwards), and have higher proportions of JE/JEX breed cattle. The outcomes of the present study provide an evidential base for the development of targeted industry-lead interventions with the aim of ending the routine early slaughter of calves.

Project description:Persistence of bovine tuberculosis (bTB) in cattle is an important feature of Mycobacterium bovis infection, presenting either as herd recurrence or local persistence. One risk factor associated with the risk of recurrent episodes is the severity of a previous bTB episode (severity reflecting the number of bTB reactors identified during the episode). In this study, we have sought to identify predictors that can distinguish between small (less severe) and large (more severe) bTB episodes, and to describe nationally the severity of bTB episodes over time. The study included descriptive statistics of the proportion of episodes by severity from 2004 to 2015 and a case-control study. The case-control study population included all herds with at least one episode beginning in 2014 or 2015, with at least two full herd tests during the episode and a minimum herd-size of 60 animals. Case herds included study herds with at least 13 reactors whereas control herds had between 2 to 4 (inclusive) reactors during the first 2 tests of the episode. A logistic regression model was developed to identify risk factors associated with a large episode. Although there has been a general trend towards less severe herd bTB episodes in Ireland over time (2004-2015), the proportion of large episodes has remained relatively consistent. From the case-control study, the main predictors of a large episode were the year the episode started, increasing herd-size, previous exposure to bTB, increasing bTB incidence in the local area, an animal with a bTB lesion and a bTB episode in an associated herd. Herds that introduced more animals were more likely to have a smaller bTB episode, reflecting the reduced risk of within-herd transmission when an episode was due to an introduced infected bTB animal. Some of the risk factors identified in this study such as reactors in previous bTB episodes, herds with an associated herd undergoing a bTB episode, herds in high incidence areas etc. may help to target future policy measures to specific herds or animals for additional surveillance measures. This information has important policy implications.

Project description:BackgroundA discrete time, stochastic, compartmental model simulating the spread of Mycoplasma hyopneumoniae within a batch of industrially raised pigs was developed to understand infection dynamics and to assess the impact of a range of husbandry practices. A 'disease severity' index was calculated based on the ratio between the cumulative numbers of acutely and chronically diseased and infectious pigs per day in each age category, divided by the length of time that pigs spent in this age category. This is equal to the number of pigs per day, either acutely or chronically infectious and diseased, divided by the number of all pigs per all days in the model. The impact of risk and protective factors at batch level was examined by adjusting 'acclimatisation of gilts', 'length of suckling period', 'vaccination of suckling pigs against M. hyopneumoniae', 'contact between fattening pigs of different age during restocking of compartments' and 'co-infections in fattening pigs'.ResultsThe highest 'disease severity' was predicted, when gilts do not have contact with live animals during their acclimatisation, suckling period is 28 days, no vaccine is applied, fatteners have contact with pigs of other ages and are suffering from co-infections. Pigs in this scenario become diseased/infectious for 26.1 % of their lifetime. Logistic regression showed that vaccination of suckling pigs was influential for 'disease severity' in growers and finishers, but not in suckling and nursery pigs. Lack of contact between gilts and other live pigs during the acclimatisation significantly influenced the 'disease severity' in suckling pigs but had less impact in growing and finishing pigs. The length of the suckling period equally affected the severity of the disease in all age groups with the strongest association in nursery pigs. The contact between fatteners of different groups influenced the course of infection among finishers, but not among other pigs. Finally, presence of co-infections was relevant in growers and finishers, but not in younger pigs.ConclusionThe developed model allows comparison of different prevention programmes and strategies for controlling transmission of M. hyopneumoniae.

Dataset Information

Post-mortem surveillance of bovine tuberculosis in Ireland: herd-level variation in the probability of herds disclosed with lesions at routine slaughter to have skin test reactors at follow-up test.

Publications

Post-mortem surveillance of bovine tuberculosis in Ireland: herd-level variation in the probability of herds disclosed with lesions at routine slaughter to have skin test reactors at follow-up test.

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