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Preventive Veterinary Medicine
Elsevier
Preventive Veterinary Medicine

Elsevier

0167-5877

Preventive Veterinary Medicine/Journal Preventive Veterinary MedicineSCIISTP
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    Putting sheep scab in its place: A more relational approach

    Smith A.E.O.Doidge C.Lovatt F.Kaler J....
    12页
    查看更多>>摘要：? 2022 The AuthorsSince the reintroduction of sheep scab within the UK, its prevalence has increased despite several industry-led initiatives to control and manage the disease. Some studies have suggested that initiatives or policies should instead focus on specific places, such as geographically high-risk areas for sheep scab, which could allow for a more targeted approach. However, this risk of sheep scab has been measured in set geographical areas, without the reference to the interplay of topography, host, pathogen and the way in which humans socially and culturally define risk and place, potentially limiting the effectiveness of preventative initiatives. Therefore, the aim of the current study was to understand how place influences sheep farmers’ approaches to the identification and management of the risk of sheep scab in their flocks. Qualitative data was collected from 43 semi-structured interviews with sheep farmers from England, Scotland, and Wales and was analysed by using the constant comparative approach. The codes were grouped into four concepts that influenced farmers' decision-making strategies for sheep scab control: perception of place; risk identification; risk categorisation; and risk management. These concepts were used as an analytical framework to identify three different 'places': 'uncontrollable places’, 'liminal places’ and 'protective places’. Each place reflects a different sheep scab control strategy used by farmers and shaped by their perceptions of place and risk. The ‘uncontrollable places’ category represented farmers who were located in areas that were geographically high-risk for sheep scab and who experienced a high frequency of sheep scab infestations in their flocks. The risk posed by their local landscape and neighbouring farmers, who neglected to engage in preventative behaviours, led them to feel unable to engage in effective risk management. Thus, they viewed scab as uncontrollable. The farmers within the ‘liminal places’ category were characterised as farmers who were located in high-risk areas for sheep scab, but experienced low levels of sheep scab infestations. These farmers characterised the risks associated with sheep scab management in terms of needing to protect their reputation and felt more responsibility for controlling sheep scab, which influenced them to engage in more protective measures. The farmers within the ‘protective places’ category were characterised as farming within low-risk areas and thus experienced a low level of sheep scab infestations. These farmers also described their risk in terms of their reputation and the responsibility they held for protecting others. However, they sought to rely on their low geographical risk of sheep scab as a main source of protection and therefore did not always engage in protective measures. These results suggest that place-based effects have significant impacts on sheep farmers’ beliefs and behaviours and thus should be considered by policymakers when developing future strategies for sheep scab control.
      原文链接:
    • NSTL
    • Elsevier

    Seroepidemiology of selected transboundary animal diseases in goats in Zambia

    Lysholm S.Lindahl J.F.Johansson E.Bergkvist P.K....
    14页
    查看更多>>摘要：? 2022 The AuthorsTransboundary pathogens of goats present significant constraints to the livelihoods of millions of farmers in countries such as Zambia. Consequently, this study aimed to investigate the seroprevalence of Mycoplasma capricolum subsp. capripneumoniae (Mccp), foot and mouth disease virus (FMDV), Brucella spp., Crimean Congo haemorrhagic fever virus (CCHFV), and Rift Valley fever virus (RVFV) in Zambian goats. Another aim was to identify associations between seroprevalence and different predictor variables, such as trade and border proximity. From September to October 2019, 962 serum samples were collected from goats in seven Zambian districts, four of which have an international border while the remaining three do not. A questionnaire survey was conducted with each household, focusing on trade routines, management strategies and herd disease history. Animal-level seroprevalence adjusted for herd-level clustering was 8.2 % (95 % confidence interval [CI] 7.5–9.0) for Mccp, 12.9% (95% CI 12.0–13.7) for FMDV, 13.0 % (95% CI 12.1–13.9) for Brucella spp., 3.3 % (95% CI 2.8–3.7) for CCHFV, and 0.4 % (95 % CI 0.3–0.7) for RVFV. The association between herd-level seroprevalence and border proximity and trade appeared negligible, with the exception of selling goats at least twice a year which was identified as a potential risk factor for Brucella spp. (OR 4.1, 95 % CI 1.1–16.0, p = 0.040). In addition, a positive association between herd-level seroprevalence of FMDV and a herd size of 21 goats or more (OR 3.3, 95 % CI 1.0–11.1, p = 0.049) was detected. Also, positive associations between animal-level seroprevalence of Brucella spp. and increasing age (OR 7.7, 95 % CI 1.5–40.7, p = 0.016), and CCHFV and keeping pigs in the household (OR 2.7, 95 % CI 1.0–7.1, p = 0.044), were found. For FMDV (OR 3.8, 95 % CI 1.4–10.9, p = 0.011) and Brucella spp. (OR 4.5, 95 % CI 1.2–17.3, p = 0.031) on the other hand, animal-level seroprevalence was significantly higher in households without pigs. To the best of the authors’ knowledge, this is the first study to describe the presence of antibodies for CCPP and CCHF in the Zambian goat population. While the association between seroprevalence and trade and border proximity generally appeared negligible, it is recommended that their influence is further evaluated in future studies, preferably through in-depth longitudinal studies incorporating impacts of different biosecurity measures and trade variations, linked to for example seasonality and trade peaks.
      原文链接:
    • NSTL
    • Elsevier

    Stability selection for mixed effect models with large numbers of predictor variables: A simulation study

    Hyde R.O'Grady L.Green M.
    8页
    查看更多>>摘要：? 2022 The AuthorsCovariate selection when the number of available variables is large relative to the number of observations is problematic in epidemiology and remains the focus of continued research. Whilst a variety of statistical methods have been developed to attempt to overcome this issue, at present very few methods are available for wide data that include a clustered outcome. The purpose of this research was to make an empirical evaluation of a new method for covariate selection in wide data settings when the dependent variable is clustered. We used 3300 simulated datasets with a variety of defined structures and known sets of true predictor variables to conduct an empirical evaluation of a mixed model stability selection procedure. Comparison was made with an alternative method based on regularisation using the least absolute shrinkage and selection operator (Lasso) penalty. Model performance was assessed using several metrics including the true positive rate (proportion of true covariates selected in a final model) and false discovery rate (proportion of variables selected in a final model that were non-true (false) variables). For stability selection, the false discovery rate was consistently low, generally remaining ≤ 0.02 indicating that on average fewer than 1 in 50 of the variables selected in a final model were false variables. This was in contrast to the Lasso-based method in which the false discovery rate was between 0.59 and 0.72, indicating that generally more than 60% of variables selected in a final model were false variables. In contrast however, the Lasso method attained higher true positive rates than stability selection, although both methods achieved good results. For the Lasso method, true positive rates remained ≥ 0.93 whereas for stability selection the true positive rate was 0.73–0.97. Our results suggest both methods may be of value for covariate selection with high dimensional data with a clustered outcome. When high specificity is needed for identification of true covariates, stability selection appeared to offer the better solution, although with a slight loss of sensitivity. Conversely when high sensitivity is needed, the Lasso approach may be useful, even if accompanied by a substantial loss of specificity. Overall, the results indicated the loss of sensitivity when employing stability selection is relatively small compared to the loss of specificity when using the Lasso and therefore stability selection may provide the better option for the analyst when evaluating data of this type.
      原文链接:
    • NSTL
    • Elsevier

    A cost-benefit analysis of Vietnam's 2006–2010 foot-and-mouth disease control program

    Van Ha P.Dang Van K.Nguyen H.-T.-M.Do H....
    8页
    查看更多>>摘要：? 2022 Elsevier B.V.Foot-and-mouth disease (FMD) is arguably the most damaging animal disease, affecting three-quarters of the global livestock population. This paper provides a cost-benefit analysis of the first five-year program that used vaccination to contain and control FMD in an endemic country, Vietnam. Our spatial and dynamic model to simulate FMD outbreaks fully considered the distance among livestock premises, their herd sizes, and composition, all of which significantly affect FMD transmission. Our program benefit was consistently estimated due to the Law of Large Number and the design of pairing the control and treatment scenarios which allowed capturing the true benefit of each outbreak realization. The data used to monetize the program benefit were largely drawn from Vietnam's context and statistics, thus obviating the need to make many potentially undue assumptions. Meanwhile, the program costs were actual spending and allocated budget. We found that the vaccination program is highly cost-effective for Vietnam, yielding a net present value of US$136 million (in 2006 prices) over five years and a benefit-cost ratio of 5.7. Our results were robust to different assumptions about the vaccine effectiveness of the livestock unit.
      原文链接:
    • NSTL
    • Elsevier

    Estimation of the accuracy of an ELISA test applied to bulk tank milk for predicting herd-level status for Salmonella Dublin in dairy herds using Bayesian Latent Class Models

    Um M.M.Arsenault J.Dufour S.Fecteau G....
    13页
    查看更多>>摘要：? 2022 Elsevier B.V.Enzyme-Linked Immunosorbent Assay (ELISA) test is commonly used for detection of antibodies to Salmonella Dublin in individual bovine milk samples. However, little is known about its accuracy when used on bulk tank milk for determining herd-level S. Dublin status and when evaluated without assuming a perfect reference test. The objectives of this study were: i) to estimate the herd prevalence of S. Dublin among dairy cattle herds in Québec, Canada; ii) to estimate the herd sensitivity and specificity of a commercially available ELISA test when used on bulk milk; iii) to examine how the diagnostic test accuracy varies with different bulk milk ELISA cut-offs; and (iv) to assess the added value of combining ELISA screening of bulk milk and individual serum of 10 animals for determining S. Dublin herd status. A cohort of 302 dairy herds selected in three regions (population 1) and 58 herds that have already tested positive to S. Dublin (population 2) were recruited. A total of 715 bulk milk samples and 7150 individual blood samples from cattle over 3 months old (10 animals per herd) sampled on two occasions were collected. Testing was conducted using PrioCHECK? Salmonella Ab bovine Dublin ELISA test for milk (Bmilk ELISA: test under investigation) and for serum of 10 individual animals (Serum10 ELISA: imperfect reference test) to determine the herd-level S. Dublin status. A latent class model for two populations, two tests, allowing for conditional dependence between tests was fit within a Bayesian framework. At cut-off PP % ≥ 15 for a Bmilk ELISA, which is used by provincial authorities, the herd prevalence of S. Dublin estimated using informative prior was 6.8 % (4.3–9.9) in population 1. The herd sensitivity and specificity estimates (95 % Bayesian Credibility Intervals) for Bmilk ELISA were 40.6 % (15.6–88.8) and 91.9 % (88.3–95.8), respectively. Positive and negative predictive values of Bmilk ELISA applied in population 1 were 26.4 % (8.5–60.2) and 95.8 % (92.1–99.2), respectively. Increasing Bmilk ELISA cut-offs had little influence on predictive values. The combination of both ELISA tests did not improve the diagnostic accuracy of S. Dublin. Our study shows that a test-positive herd based on a single bulk milk sample would require complementary tests for status confirmation. However, a test-negative herd could be classified as true negative with a high certainty.
      原文链接:
    • NSTL
    • Elsevier