Integrating microbiology and modelling to determine the source of Campylobacter infection in the broiler house and develop interventions

弯曲杆菌是发达国家公认的细菌性肠胃炎的最大病因。2009年大不列颠的报告率显示超过64000例，在苏格兰和英格兰和威尔士比前一年增加了30%和14%，这种情况一直持续到2010年。由于弯曲杆菌病的报告严重不足，2009年的实际病例数可能接近45万。此外，大约10%的报告病例住院治疗。由于弯曲杆菌的感染率在2000年至2005年期间一直在下降，因此这一增长更加令人失望。我们和其他人进行的分子菌株分型已经确定，家禽是这种感染的最重要的来源，在人类身上发现的最常见的类型在鸡身上也最常见。对零售家禽的研究表明，这种肉类中弯曲杆菌的流行率超过65%，主要感染途径是食用未煮熟的肉类或与未煮熟的食物交叉污染。为了减轻这种人类疾病的负担，必须采取行动减少弯曲杆菌在家禽中的负荷，食品标准局、Defra和BBSRC都将其确定为主要优先事项。英国食品标准局正在考虑降低零售生鸡肉中弯曲杆菌含量的目标，该目标将于2015年4月实现。该目标将通过利益相关者的参与和伙伴关系的工作来设定和实现。国外家禽业的干预措施已导致人类感染率急剧下降。例如，冰岛采用了冷冻阳性尸体的方法，新西兰采用了干预措施和法规，美国改进了卫生条件，并对尸体使用氯洗涤。然而，英国工业在很大程度上无法实现减排。尽管诸如家禽疫苗接种等战略在长期内具有吸引力，但更直接地说，通过对肉鸡养殖场进行知情的生物安全干预可能最容易实现控制。事实上，英国生产商普遍认识到，在强大的生物安全仍未被破坏的地方，如用于生产孵化成肉鸡的宝贵（大）亲本鸟，弯曲杆菌的定殖是罕见的。在高通量肉鸡生产中，定植经常发生，并且本文提出的新型生物安全控制可以发挥重要作用。我们对人类弯曲杆菌感染源的研究不仅确定了肉鸡是弯曲杆菌感染的主要来源，而且还发现弯曲杆菌在人类和鸡、牛、羊、野生鸟类、猪等宿主中的分布非常明显，有些菌株在几种宿主中是共同的。本提案旨在通过使用建模方法更好地了解肉鸡弯曲杆菌潜在来源的相对重要性。假设在这一过程中，一些弯曲杆菌菌株和一些弯曲杆菌储存库比其他菌株更重要，只有通过量化它们的相对重要性和它们之间的相互作用，才有可能在肉鸡房中强有力地确定弯曲杆菌的来源，从而引入有效的措施来防止这些鸟类在生产过程中定植。研究结果将有助于制定政策（如操作守则），以确定哪些控制措施最有效地保持肉鸡舍无弯曲杆菌。这将通过改进耕作方式对工业产生强烈影响。

Campylobacter is the largest cause of recognised bacterial gastroenteritis in the developed world. The 2009 reporting rates for Great Britain show more than 64 000 cases, an increase of 30% in Scotland and 14% in England & Wales on the previous year, that has continued into 2010. Because there is substantial under-reporting of campylobacteriosis, the actual number of cases in 2009 is likely to be closer to 450 000. Further, about 10% of reported cases are hospitalised. This rise is all the more disappointing because rates of infection with Campylobacter had been falling between 2000 and 2005. Molecular strain typing, by us and others, has identified that poultry is significantly the most important source of this infection with the most common types found in human beings also being the most common in chickens. Studies on retail poultry show a prevalence of Campylobacter in this meat of over 65% with the main routes of infection being eating improperly cooked meat or cross-contamination to uncooked foods. To reduce this burden of human disease, action must be taken to reduce Campylobacter loads in poultry and The Food Standards Agency, Defra and BBSRC have all identified this as a major priority. The FSA is considering targets for the reduction in levels of Campylobacter in raw chicken at retail, to be achieved by April 2015. The target will be set and achieved through stakeholder engagement and partnership working. Interventions in the poultry industry abroad have resulted in dramatic decreases in human infection rates. For example, in Iceland where freezing of positive carcasses is used, in New Zealand where interventions and regulations were introduced and in the USA where improved hygiene and the use of chlorine washes for carcasses has been implemented. However, UK industry has largely been unable to achieve reductions. Although strategies such as poultry vaccination are attractive in the longer term, more immediately it will be through informed biosecurity interventions on broiler farms that control is likely to be most readily achieved. Indeed UK producers widely recognise that where robust biosecurity remains unbreached, as for the valuable (grand)parent birds that are used to produce the eggs that hatch into broilers, then Campylobacter colonisation is uncommon. It is in the high throughput broiler production that colonisation regularly occurs and where novel biosecurity controls, as proposed here, could play an important role. Our previous studies of the sources of Campylobacter infection in humans not only identified the principal source as broiler chickens, it also identified that the distribution of Campylobacter strains found in humans and in the reservoirs of chicken, cattle, sheep, wild birds, pigs etc, were quite distinct with some strains common to several hosts. This proposal seeks to better understand the relative importance of the potential sources of Campylobacter in broilers by using a modelling approach. The hypothesis is that some Campylobacter strains and some Campylobacter reservoirs are much more important than others in this process and that it is only by quantitating their relative importance and their interaction with each other that it will be possible to robustly identify the sources of Campylobacter in the broiler house and hence introduce effective measures to prevent the colonisation of these birds during production. The findings will enable policy to be developed (e.g. code of practice) to define which control measures are most effective in keeping broiler houses Campylobacter free. This will strongly influence industry through improved farming practice.