Production systems bird welfare and endemic disease affect the susceptibility of chickens to Campylobacter

弯曲杆菌呈是非常重要的食源性肠道致病菌，估计每年在英国造成超过600，000例感染，约100人死亡。据估计，弯曲杆菌感染每年给英国经济造成约10亿英镑的损失。感染的特点是急性，有时是带血腹泻，特别是在儿童中。在过去的几年里，老年人的感染病例明显增加，特别是那些患有肠癌的人，感染可能是致命的。鸡肉是人类弯曲杆菌感染的最重要来源和媒介，在英国销售的鸡中约80%是弯曲杆菌阳性的。弯曲杆菌是鸡和其他食用动物肠道的天然居民。鸡肉的污染有两种形式。尸体表面可能携带高水平的弯曲杆菌，这可能导致家庭和商业餐饮的交叉污染。这是感染的一个重要风险因素。然而，也许更重要的是，弯曲杆菌已经从高达27%的测试鸡的深层肌肉组织中回收。此外，肝脏组织也经常受到污染。在这些组织中，细菌将被更好地保护免受烹饪的影响。未煮熟的鸡肉和鸡肝是弯曲杆菌感染的重要媒介。为了改善英国的公共卫生，减少销售中受污染的鸡的数量至关重要。拟议的研究将检查英国养鸡的不同系统，以确定具有成本效益的农场控制方案。我们的工作将侧重于在圈养系统中集中饲养的鸡，因为这些鸡占英国市场的90%。这项工作将与英国三大家禽生产商合作，英国所有主要食品零售商都给予财政支持。这项拟议的研究建立在过去研究的基础上，这些研究表明，在更高福利制度下饲养的鸡（肉鸡）感染弯曲杆菌的可能性低于密集饲养的鸟类。福利较高的系统通常使用生长较慢的鸟类和饲养较少的鸟类比更密集的系统。我们的工作表明，在更密集的系统中饲养的鸟类福利较差，如地方病和一般健康和腿部问题的高发病率所示。这可能解释了为什么这些鸟类更有可能是弯曲杆菌阳性，因为健康和/或福利不佳的鸟类更容易受到这些细菌的影响。这些差异可能是由于使用的鸟和/或内部环境造成的，我们将确定这一点。我们的实地工作也可能表明，生长较慢的鸟类可能天生就对弯曲杆菌更具抵抗力。我们将对在不同系统下饲养的鸡群进行纵向研究，并确定何时鸟类首次成为弯曲杆菌阳性，并将其与鸟类健康和福利的变化联系起来。我们还将确定弯曲杆菌从鸟类肠道传播到肝脏等可食用组织是否发生在农场，以及是否与地方病的不良福利有关。我们的目标是为英国家禽业提供基于科学和具有成本效益的控制方案，这将有助于满足客户需求，并遵守即将出台的旨在减少弯曲杆菌阳性鸡数量的欧盟立法。

Campylobacter spp. are extremely important food borne enteropathogenic bacteria, estimated to cause over 600,000 cases of infection in the UK each year with around 100 deaths. It is estimated that Campylobacter infections cost the UK economy around £1 billion per year. Infection is characterised by acute and sometimes bloody diarrhoea, particularly in children. The last few years have seen a marked rise in cases in compromised elderly populations and in such people, particularly those with bowel cancer, infection can be fatal. Chicken meat is the most important source and vehicle for human Campylobacter infections and around 80% of chickens on sale in the UK are Campylobacter-positive. Campylobacter are natural inhabitants of the intestinal tract of chickens and other food animals. Contamination of chicken meat takes two forms. Carcass surfaces can carry high levels of Campylobacter and this can lead to cross-contamination in both domestic and commercial catering. This is an important risk factor for infection. However, and perhaps more importantly, Campylobacter have been recovered from deep muscle tissues of up to 27% of chickens tested. Furthermore, liver tissues are also commonly contaminated. In these tissues the bacteria will be better protected from the effects of cooking. Undercooked chicken meat and chicken liver pate are internationally important vehicles of Campylobacter infection. To improve public health in the UK it is essential that the number of contaminated chickens on sale is reduced. The proposed research will examine the different systems in which UK chickens are grown to identify cost-effective farm-based control options. Our work will focus on chickens reared intensively in housed systems as these comprise ~90% of the UK market. The work will be in collaboration with the three biggest poultry producers in the UK and all the major UK food retailers are giving financial support. The proposed research builds on past studies which showed that chickens (broilers) reared under higher welfare systems are less likely to have Campylobacter than birds reared more intensively. The higher welfare systems generally use slower-growing birds and stock houses with fewer birds than the more intensive systems. Our work showed that birds reared in the more intensive system had poorer welfare, as shown by high rates of endemic disease and general health and leg problems. This might explain why these birds were more likely to be Campylobacter-positive, as birds compromised by poor health and/or welfare are more susceptible to these bacteria. These differences might be due to the birds used and/or the in-house environment and we will determine this. Our field work might also indicate that the slower-growing bird types may be inherently more Campylobacter-resistant. We will conduct longitudinal studies on flocks reared under different systems and determine when birds first become Campylobacter-positive and relate this to changes in bird health and welfare. We will also determine whether the spread of Campylobacter from the intestine of the birds to edible tissues like liver occurs on farm and if it is linked to poor welfare for endemic disease. Our aim is to provide the UK poultry industry with science-based and cost-effective control options, which will help it meet customer demands and comply with forth-coming EU legislation aimed at reducing the number of chickens that are Campylobacter-positive.