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

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.

Chicken is the source of ~80% of human Campylobacter infections. The bacteria are found on carcass surfaces at high levels and in muscle and liver tissues. Undercooked chicken meat is an important vehicle of Campylobacter infection. It is essential that the number of contaminated chickens is reduced. The proposed research will examine different intensive systems in which UK chickens are grown and determine reasons for the observed differences in Campylobacter status. This project results from a direct request from the UK poultry industry. This proposal brings together modellers, microbiologists, molecular biologists, retailers and poultry producers in a unique combination to address global risks to human health associated with interactions between broiler production systems, endemic disease and physiological state of birds. Our past work showed that chickens reared under higher welfare systems are less likely to have Campylobacter than standard birds. The higher welfare systems use birds that grow more slowly and which are stocked at a lower density. As well as lower Campylobacter levels, the higher welfare birds had better health and this may protect them against Campylobacter. We seek to determine, through field studies, which of bird genotype/growth and/or the in-house environment determine Campylobacter status and to identify the mechanisms by which Campylobacter leave the chicken gut and infect edible tissues. We will use a combined modelling and molecular approach to investigate factors that improve resistance to Campylobacter, reduce risk of colonization and extra-intestinal spread in UK broilers. We will undertake laboratory studies to determine the susceptibility of commonly used broiler chickens to C. jejuni and the major endemic poultry pathogen avian pathogenic E. coli (APEC). Infection with E. coli not only increases the risk of broilers having Campylobacter, but is also strongly correlated with spread from the gut.

Campylobacter is the most important food borne zoonosis in the UK and the wider EU. In the UK it is estimated that there are 600000 cases of infection in the UK each year and that Campylobacter infection costs the UK economy ~£1 billion per year. Chicken is overwhelmingly the most important vehicle for human infection and is believed to be responsible for up to 80% of infections. Furthermore, ~80% of chickens on sale in the UK are Campylobacter-positive. Contaminated chicken presents two health threats. Surface contamination levels can reach 109 cfu per carcass and contamination of deep muscle and liver tissues has been reported in up to 27 and 60% of samples tested respectively. The project seeks to better understand the impact of broiler chicken production systems, the resistance of the birds to infection with Campylobacter and its in vivo behaviour in the bird. We have shown that birds reared in higher welfare housed systems such as the RSPCA-backed Freedom Foods scheme, have lower Campylobacter levels and fewer risk factors for Campylobacter colonisation such as endemic diseases and poor gut health than birds reared in standard production systems. We seek to determine why these commonly used production systems differ so markedly and we will be determining the single and combined impacts of bird genotype/growth rate, endemic disease and bird stocking density, which affects the in-house environment. By comparing the different systems, we will be able to identify farm-based control measures that will reduce levels of Campylobacter in UK poultry and also improve the welfare of the birds. By better understanding the epidemiology of a major poultry endemic disease, APEC, measures can be identified to better control it. This will improve bird health and welfare, increase industry profitability and reduce the carbon footprint of UK poultry production. The project is in partnership with the UK poultry industry and all major UK retailers. Thus the beneficial impacts of our work can quickly be transferred to stakeholders.