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

弯曲杆菌是极其重要的食源性肠致病菌，据估计，英国每年有60多万例感染病例，其中约100人死亡。据估计，弯曲杆菌感染每年使英国经济损失约10亿英镑。感染的特点是急性腹泻，有时带血腹泻，特别是儿童。过去几年，身体虚弱的老年人群的病例明显增加，在这些人群中，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最重要的来源和载体，在英国出售的鸡肉中约有80%呈弯曲杆菌阳性。弯曲杆菌是鸡和其他食用动物肠道的天然居民。鸡肉污染有两种形式。胴体表面可能携带大量弯曲杆菌，这可能导致家庭和商业餐饮业的交叉污染。这是感染的一个重要危险因素。然而，也许更重要的是，弯曲杆菌已经从27%的测试鸡的深层肌肉组织中恢复。此外，肝组织也经常受到污染。在这些组织中，细菌将更好地免受烹饪的影响。未煮熟的鸡肉和鸡肝酱是国际上弯曲杆菌感染的重要载体。为了改善英国的公众健康，必须减少出售的受污染鸡的数量。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。我们的工作将集中在密集饲养的鸡，因为这些鸡占英国市场的90%。这项工作将与英国三家最大的家禽生产商合作，英国所有主要的食品零售商都将提供财政支持。拟议的研究建立在过去的研究基础上，这些研究表明，在较高福利制度下饲养的鸡（肉鸡）比密集饲养的鸡更不可能感染弯曲杆菌。福利较高的系统通常使用生长较慢的鸟类，并且与集约化系统相比，禽鸟较少的鸡舍。我们的工作表明，在更密集的系统中饲养的鸟类福利较差，地方性疾病和一般健康和腿部问题的发生率较高。这也许可以解释为什么这些鸟类更有可能是弯曲杆菌阳性，因为健康状况不佳和/或福利较差的鸟类更容易感染这些细菌。这些差异可能是由于使用的鸟类和/或内部环境，我们将确定这一点。我们的野外工作也可能表明，生长较慢的鸟类可能天生就更能抵抗弯曲杆菌。我们将对在不同系统下饲养的鸡群进行纵向研究，确定鸟类何时首次呈弯曲杆菌阳性，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禽类肠道传播到肝脏等可食用组织是否发生在农场，以及它是否与地方性疾病的不良福利有关。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.