Susceptibility of broiler chickens to Campylobacter: impacts of the gut environment and immune status on colonisation

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Chicken is the main source of human Campylobacter and this threat must be reduced. The proposed work will determine mechanisms behind the delay before broiler chickens become Campylobacter-positive in housed flocks. The project is in partnership with poultry producers to identify cost-effective control measures to protect chickens against Campylobacter.

Past work suggested that maternal antibodies provide chicks with some protection against Campylobacter in early life. However, this was done in isolation and other protective factors were not studied. Campylobacter-negative chicks can have gut bacteria that inhibit C. jejuni. In most flocks, the 'protective bacteria' were not present when birds reached 3-4 weeks of age and flocks rapidly became Campylobacter-positive.

We will determine whether maternally-derived antibodies and/or gut microbiota and/or gut architecture is the most important in determining broiler susceptibility to Campylobacter. We will study Ross 308 birds, the most common type in the UK. The field studies will relate changes in naturally acquired maternal anti-Campylobacter antibodies and gut microbiota with events in flock management, like diet change and with the presence of Campylobacter. State of the art techniques will be used to determine microbiota.

Laboratory experiments will test field-generated hypotheses in a controlled manner. B-cell deficient breeders will be produced by surgical bursectomy. This creates B-cell- and thus antibody-deficient hens. These will be used to form breeding flocks producing progeny deficient in maternal antibodies. We can then determine definitively the role of maternal antibodies in the resistance of chicks to Campylobacter. We will use modelling to investigate dynamics of chicken gut microbiota and its impact and maternal antibodies as direct and proximal drivers of colonisation in commercial chicken production. These models will be used to identify targets for mitigating Campylobacter colonisation.

Campylobacter is the most important food borne zoonosis in the UK and the wider EU. In the UK it is estimated that there are 700000 cases of infection each year and that chicken-associated 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. ~80% of chickens on sale in the UK are Campylobacter-positive. Contaminated chicken presents two health threats. Surface contamination levels can be very high 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 processes that occur during the early development of chickens that leads them to become colonised by Campylobacter.
We seek to accurately determine when broiler flocks first become Campylobacter-positive, as there is a delay before this happens, and will be investigating the roles in this process of maternally acquired anti-Campylobacter antibodies and changes in gut microbiota and gut architecture for the first time all together. Such processes that are driven by bird age and/or diet and this project proposes to study these by laboratory studies, but also importantly in the field on commercial farms. By determining the reasons for changes to susceptibility to this major zoonotic pathogen, we will be able to identify farm-based control measures that will reduce levels of Campylobacter in UK poultry and not rely on biosecurity alone. In particular, our work will importantly inform studies on the use of vaccines and the use of pre- and/or probiotics. 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.