Improving the control of liver fluke infection in cattle in the UK

肝吸虫是一种常见的寄生虫，影响英国的羊和牛。它在世界各地都有发现，在一些国家也会影响人类，导致严重的，有时甚至是致命的疾病。感染了吸虫的牛体重下降、贫血、嗜睡并停止生产。这对动物的福利造成了严重影响，对农民造成了严重的经济后果。据认为，吸虫每年给英国农业造成的直接损失至少为3亿英镑，但实际损失可能要高得多。在过去的10年里，Fluke变得越来越普遍，部分原因是我们不断变化的天气模式，潮湿的夏季和温和的冬季有利于寄生虫及其载体——一种泥蜗牛的发展，这种寄生虫在英国很常见。在最近的一项研究中，我们发现75%的奶牛群有吸虫感染的证据。预计未来的气候变化将对感染流行、改变流行病学和增加发病率产生重大影响。牲畜流动的增加以及农场管理和环境计划的变化加剧了这一问题。控制片形吸虫病的药物范围有限。只有一种药物——三氯苯达唑（TCBZ）对寄生虫的早期、晚期和成年阶段有效，并广泛用于疾病的预防和治疗。越来越多的证据表明，吸虫种群对TCBZ具有耐药性，此外，欧洲药品管理局最近修订了对用于治疗吸虫的药物的建议，现在禁止对奶牛使用这些药物。在一年中的特定时间有针对性地使用药物将减缓耐药性的发展并减少药物的总使用量，但是，如果我们要制定依靠改进的农场管理做法而不是仅仅依靠药物的控制规划，更好地了解流行病学和疾病的传播是至关重要的。这最终将成为控制牛临床和亚临床疾病的可持续和具有成本效益的方法，也是畜牧业的明确愿望。应养殖业的具体要求，该项目的目的是为牛肉和奶牛场制定新的、可持续的定制控制方案，以减少与吸虫感染有关的损失。为了实现这一目标，我们必须首先开发诊断测试来识别受感染的畜群。我们已经有了很好的工具，我们可以使用牛奶样本来检测受感染的奶牛群，但我们需要适用于肉牛群的类似测试。此外，我们还注意到一种新出现的寄生虫问题，即瘤胃吸虫。目前尚不清楚这种寄生虫是否会引起疾病，但它有可能干扰我们正在开发的吸虫诊断测试。因此，我们还将开发一种瘤胃吸虫的分子检测方法。其次，我们将开发一个系统来对蜗牛栖息地进行分类，该系统可用于分析区域地理尺度上的卫星地图，以避免访问每个农场来调查蜗牛栖息地的需要。我们还将研究牛的行为如何影响寄生虫如何到达蜗牛宿主，并从蜗牛宿主回到牛身上。这些都是农场感染吸虫的危险因素。其他风险因素，特别是饲养方法，物理和环境因素将从250个农场的研究中获得，并将这些数据输入统计和数学模型，以从理论上确定这些因素中哪些是决定农场是否有吸虫的最重要因素。同时，我们将评估改变这些实践的成本效益。最后，我们将进行一项试验，以评估改变农场做法是否能有效降低感染水平。我们正在与英国农业征税委员会合作，实施对吸虫感染的改进控制，以造福英国牲畜养殖的动物健康、福利和盈利能力。

Liver fluke is a common parasite that affects sheep and cattle in the UK. It is found throughout the world and in some countries it affects humans too, causing serious and sometimes fatal disease.Fluke infected cattle lose weight, become anaemic, lethargic and stop being productive. This has a serious effect on the welfare of the animal and serious economic consequences for the farmer. It is thought that fluke costs UK agriculture at least £300million pounds a year through direct losses, but real costs are probably much higher. Fluke has become much more common over the past 10 years, due in part to our changing weather patterns, wet summers and mild winters favour the development of the parasite and its vector - a mud snail, found commonly throughout Britain. In a recent study we found 75% of dairy herds had evidence of fluke infection. Future climate change is predicted to have a significant impact on prevalence of infection, changing the epidemiology and increasing incidence of disease. Increased cattle movements and changes to both farm management and environmental schemes are exacerbating the problem. A limited range of drugs is available to control fasciolosis. Only one drug - triclabendazole (TCBZ), is effective against early and late juvenile and adult stages of the parasite and is used extensively for prophylaxis and treatment of disease. There is growing evidence of resistance to TCBZ in fluke populations, moreover the European Medicines Agency has recently revised its advice on drugs used to treat fluke such that they are now contra-indicated in dairy animals.Targeted use of drugs, at specific times of year will slow the development of drug resistance and reduce the overall quantity of drug used, but a better understanding of the epidemiology and transmission of disease is vital if we are to develop control programmes that rely on improved on farm management practises rather than depending solely on drugs. This ultimately will be a sustainable and cost-effective way to control both clinical and sub-clinical disease in cattle and is the express desire of the livestock industry. Specifically requested by the farming industry, the purpose of this project is to produce new, sustainable, bespoke control programmes for beef and dairy farms, to reduce losses associated with fluke infection. In order to achieve this we must first develop diagnostic tests to identify infected herds. We already have good tools that we can use on milk samples to detect infected dairy herds but we need similar tests that are appropriate for beef herds. In addition we are aware of a newly emerging parasite problem, the rumen fluke. It is not clear if this parasite causes disease but it has the potential to interfere with the diagnostic tests we are developing for fluke. Therefore we will also develop a molecular test for rumen fluke.Secondly we will develop a system to categorise snail habitats that can be used to analyse satellite maps on a regional geographic scale to obviate the need to visit every farm to investigate snail habitat. We will also investigate how cow behaviour affects how the parasite gets to a snail host and from the snail host back to the cow.These are risk factors for fluke infection on a farm. Other risk factors, particularly husbandry practices, physical and environmental factors will be obtained from a study of 250 farms and these data fed into statistical and mathematical models to determine theoretically which of these factors are the most important in determining whether a farm has fluke or not. Concurrently we will assess the cost-benefit of changing these practices. Finally we will conduct a trial to evaluate if changing farm practice is effective in reducing levels of infection. We are working in partnership with the Agricultural Levy boards of the UK to implement improved control of fluke infection to benefit animal health, welfare and profitability of livestock farming in the UK.