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

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.

Poultry is the most important source of campylobacteriosis and over two-thirds of chicken at retail are contaminated by Campylobacter. A reduction in the Campylobacter loads and ideally a reduction in their prevalence in poultry at production would be the most effective measure for reducing human disease incidence. However to date, biosecurity has not proved to be entirely successful and it is thought that this may be due to the diversity of reservoirs that Campylobacter resides in. Our, and others, work has indicated that some Campylobacter strains and some Campylobacter reservoirs are probably 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 colonisation. It will be parameterised by data collected in the study. Up to eight Campylobacter strains will be selected from the top strains isolated from human cases and from chicken, cattle, sheep, pigs and wild birds. The efficacy of different strains to move from reservoir species (cattle, sheep, pigeon, chicken) to chickens will be quantitated to determine the dose response of each strain. The environmental survival of the Campylobacter strains will be estimated in a range of matrices associated with the broiler environment (faeces from cattle, sheep, pigeons and chickens; soil; water) and survival tested at two temperatures (4C and 15C) over a period of up to 3 months. This proposal will use an agent-based modelling approach, which identify how macroscale dynamics emerge from microscale interactions, to simulate the transmission of Campylobacter from the environment to the broiler house and potentially back to the environment on real farms. This will be used to quantify which interventions would be most likely to reduce broiler colonisation.

This research aims to determine whether the simple and practical removal (or reduction) of animals or birds from the immediate vicinity of broiler houses will reduce broiler colonisation by the bacterial pathogen Campylobacter. This is of relevance to human health since the strains routinely isolated from retail chicken are the most predominant in causing human infection. Societal impact: Campylobacter is the most frequently recognised cause of gastrointestinal illness both in the UK and other developed countries. The majority of cases have symptoms that are not simply mild discomfort but are exceptionally debilitating and as such result in significant distress to both patient and relatives. There is an associated significant burden on the health care system both at GP level and from the 10% of hospitalisations. Further, there is extended loss of working days which has a major impact on the local and national economy. The cost of this has been estimated at £583M in 2008 in England and Wales. Studies have identified that reductions in retail broiler contamination would result in a reduced incidence of campylobacteriosis, with a concomitant reduction in cost to individuals and to the state. Stakeholder impact: Both FSA and Defra as the major policy stakeholders have agreed to join our discussion groups. Industrial impact: We will engage with industry throughout and have already obtained preliminary agreement to collaborate with one of the leading UK broiler producers, VION Food Group Ltd, who have agreed to attend progress meetings, to allow access to their broiler farms for sampling and to comment on the practicability in implementation of findings. Should the research proposal from co-I, Dr Sparks (Defra 'Assessment of the efficacy of on-farm biosecurity measures for controlling Campylobacter') proceed, then opportunities for joint project meetings with industry would be explored. Engagement with industry in the longer term will be in the development of 'best working practices' for example through codes of practice, to implement those control measures which are identified as most effective in keeping broiler houses Campylobacter free. This will strongly influence the industry through improved farming practice. Dissemination: Articles will be submitted for publication to trade (Poultry World) and to high IF scientific journals, through press release and to the popular media and presented at academic (microbiological, modelling, poultry) and farming conferences.