A molecular epidemiological approach to combating footrot an endemic disease of sheep

羊的跛足是痛苦的。在英国，超过95%的羊群在任何时候都有大约10%的羊跛脚，其中80%的跛脚是由蹄病引起的。在任何时候，英国都有大约160万只跛脚羊。据估计，蹄病每年给英国羊业造成3100万英镑的损失，这对那些认为管理这种疾病的建议不成功的养羊户来说是一个巨大的担忧。足癣是一种传染病，由一种叫做结节性双螯菌的细菌侵入脚爪之间的皮肤引起。令人惊讶的是，人们对这种细菌如何引起疾病以及当它不引起疾病时如何存活（在羊身上或环境中）知之甚少。在过去的7年里，我们已经研究了实际方面的控制足。关键的结果是，及时用注射抗生素治疗跛脚羊的农民在他们的羊群中跛脚羊的水平较低（4%对12%），而且修剪脚（传统上用于控制蹄病）与高水平的疾病有关。这些事实表明，这种细菌在环境中的传播可能比之前在澳大利亚的研究中所怀疑的要广泛得多。我们知道环境在疾病发生中起着重要作用。D.结节虫在温暖潮湿的天气中生存得更好。我们还知道，有几种细菌菌株可以影响疾病的严重程度。然而，我们不知道环境或细菌菌株的哪些方面在确定农场疾病严重程度和持久性方面是重要的。这种细菌可以在牧场、肠道或未患病羊的脚上存活。在我们的工作中，我们收集了大量的D。从有病和无病的绵羊的拭子中提取结节状的细菌DNA，并从绵羊的脚中提取细菌DNA。我们还有大约800只母羊和它们的羔羊的两年数据。记录并调查了每一次跛行事件，并取样调查D。存在结节。从这些数据中，我们可以建立数学模型，描述羊何时跛脚，跛脚多长时间，以及影响羊恢复速度的因素，不幸的是，有些羊再次跛脚。我们提出的工作计划是分析上述数据，并增加有关D.从实验室研究中了解菌株致病的能力及其在环境中的存活情况。利用这些研究的结果和我们的模型，我们将能够找出哪些菌株的D。结节虫引起大多数疾病，以及环境和宿主在它们生存中的重要性。最终目的是提供更好的建议，控制足癣，从而降低这种疾病的发生。

Lameness in sheep is painful. In Great Britain over 95% of flocks have approximately 10% of sheep lame at any one time and 80% of this lameness is caused by footrot. There are approximately 1.6 million lame sheep in GB at any time. Footrot is estimated to cost the UK industry £31 million per year and is a huge worry to sheep farmers who do not feel that advice to manage this disease is successful. Footrot is an infectious disease caused by invasion of the skin between the claws of the foot with a bacterium called Dichelobacter nodosus. Surprisingly little is known about how this bacterium causes disease and how it survives (on the sheep or in the environment) when it is not causing disease. Over the past 7 years we have studied practical aspects of control of footrot. The key results were that farmers who treated lame sheep promptly with injectable antibiotics had low levels of lame sheep in their flocks (4% versus 12%) and also that trimming feet (traditionally used to control footrot) was associated with high levels of disease. These facts suggest that the bacteria may be much more widely spread in the environment than previously suspected from research in Australia. We know that the environment plays a role in disease occurrence. D. nodosus survives better in warm wet weather. We also know that there are several strains of the bacterium that can affect the severity of disease. However, we do not know which aspects of the environment or the bacterial strains are important in determining disease severity and persistence on farms. The bacteria may survive in pasture, in the gut or on feet of the non-diseased sheep. During our work we collected a large store of D. nodosus from swabs of sheep with and without disease and also stored bacterial DNA from the feet of sheep. We also have two years data from approximately 800 ewes and their lambs. Every occurrence of lameness has been recorded and investigated and samples taken to investigate whether D. nodosus was present. From these data we can form mathematical models that describe when a sheep became lame, how long she was lame for and factors that influenced the speed with which she recovered and, unfortunately for some, became lame again. The plan of work we propose is to analyse the data above as described and to add in new findings about D. nodosus from laboratory studies into the ability of strains to cause disease and their survival in the environment. Using results from these studies and our models we will be able to work out which strains of D. nodosus cause most disease and how important the environment and host are in their survival. The ultimate aim is to provide better advice on control of footrot and so lower the occurrence of this disease.