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The influence of liver fluke infection on production in sheep and cattle: a meta-analysis
bioRxiv - Zoology Pub Date : 2020-07-30 , DOI: 10.1101/2020.07.29.227074
Adam D. Hayward , Philip J. Skuce , Tom N. McNeilly

Liver flukes (Fasciola spp) are important parasites of sheep and cattle across the world, causing significant damage to animal health and productivity due to both acute and chronic infection. Many comprehensive reviews have discussed the results of decades of research into the impact of fluke infection on livestock performance traits such as weight gain and milk production. While fluke are considered to be important, there have been no attempts to collate previous research in a quantitative manner, and nor has there been an attempt to determine why some studies find substantial effects of fluke while others conclude that effects of fluke on animal performance are negligible. In this study, we used meta-analysis to provide quantitative estimates of the impact of liver fluke on animal performance, and to identify elements of study design that influence the conclusions of such studies. A literature search provided 233 comparisons of performance in fluke-infected and uninfected animals. We standardized these data as log response ratios and calculated effect size variances in order to weight studies by their sample size and accuracy of their estimates. We performed multi-level meta-analysis to estimate effects of fluke infection in five traits: daily weight gain (N = 77); live weight (N = 47); carcass weight (N = 84); total weight gain (N = 18) and milk production (N = 6). There were significant negative effects of fluke infection on daily weight gain, live weight and carcass weight (9%, 6% and 0.6% reductions in performance, respectively), but not total weight gain or milk production. We then used mixed-effects meta-analysis to estimate the impact of moderator variables, including host, fluke, and study design factors, on study outcomes. We found that, in general, studies that gave experimental infections found generally larger effects of fluke than observational or drug studies; younger animals were more likely to suffer the effects of fluke infection on daily weight gain; and that effects on live weight increased across the course of an experiment. Our results provide the first quantitative estimate of the importance of liver fluke on performance across studies and highlight the elements of study design that can influence conclusions. Furthermore, our literature search revealed areas of research into liver fluke that could be the subject of greater effort, and types of study that could form the basis of future meta-analyses.

中文翻译:

肝吸虫感染对绵羊和牛的生产的影响:荟萃分析

肝吸虫(Fasciola spp)是全世界绵羊和牛的重要寄生虫,由于急性和慢性感染,对动物健康和生产力造成重大损害。许多全面的评论讨论了几十年来关于吸虫感染对牲畜生产性状(如体重增加和产奶量)的影响的研究结果。虽然fl虫病很重要,但没有尝试以定量的方式整理以前的研究,也没有尝试确定为什么有些研究发现find虫病有实质性影响,而另一些人则认为fl虫病对动物性能的影响是微不足道。在这项研究中,我们使用荟萃分析来定量评估肝吸虫对动物生产性能的影响,并确定影响研究结论的研究设计要素。文献检索提供了233种在吸虫和未感染动物中的性能比较。我们将这些数据标准化为对数响应比和计算出的效应量方差,以便通过其样本量和估算准确性来进行权重研究。我们进行了多层次的荟萃分析,以评估吸虫感染对以下五个特征的影响:每日体重增加(N = 77);活体重(N = 47);体重量(N = 84); 总增重(N = 18)和产奶量(N = 6)。吸虫感染对日增重,活重和car体重量有显着的负面影响(分别使性能下降9%,6%和0.6%),但对总增重或产奶量没有影响。然后,我们使用混合效应荟萃分析来评估主持人变量(包括主持人,福禄克和研究设计因素)对研究结果的影响。我们发现,总的来说,进行实验性感染的研究发现吸虫的作用通常比观察性研究或药物研究更大。年幼的动物更容易遭受吸虫感染对日增重的影响;在整个实验过程中,对体重的影响增加了。我们的结果首次定量评估了肝吸虫对整个研究表现的重要性,并强调了可能影响结论的研究设计要素。此外,我们的文献检索揭示了对肝吸虫的研究领域可能会付出更大的努力,而研究类型则可能构成未来荟萃分析的基础。
更新日期:2020-07-31
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