Bacterial pathogens such as Campylobacter and Salmonella in chickens that can be transmitted from meat and eggs to people causing gastroentertitis which can be life threatening.
In Europe it is estimated 1 in every 100 people are infected with Campylobacter each year and that most of these cases are from infected poultry meat. Surveys have shown 70% of supermarket chicken in the UK has Campylobacter. So reducing the Campylobacter levels in chicken flocks should lead to a reduction in human cases.
Our work in Liverpool has focused on understanding how Campylobacter behaves within the chicken, how it moves between birds in flocks and importantly what type of immune response the chicken produces. Each of these is important in developing interventions we can use on farms and especially in developing vaccines which have been a success story in helping control Salmonella.
We have made 3 important findings. The first of these is that most people had considered that Campylobacter had little effect on the chickens themselves. We were able to show that infection leads to poor gut health which in turn leads to poorer welfare of the animal. Animal behaviour scientists have also built upon our work and shown infection leads to negative behavioural changes in flocks too.
Secondly we have shown that Campylobacter is very varied in how it behaves. Previously it was thought that the bacteria lived in one part of the chicken gut called the caeca, but we know that some variants can survive through the full length of the gastrointestinal system. Some variants can also spread more easily from the gut to the liver and even muscle tissue. Understanding this is important in processing poultry carcasses to reduce the risk of contamination.
Finally we now understand the immune response that chickens make to Campylobacter may be exploited by some forms of vaccination and we are working with a vaccine company to develop these vaccines.
Our work uses experimental infections in the type of chicken used commercially. Unlike many experimental systems we are not trying to model a human disease, but are re-creating what happens on farms in a controlled and contained environment. We are fortunate in having a dedicated poultry unit and expert technical staff in Liverpool.
Work with zoonotic pathogens requires high biological containment with the ability to keep chickens under high welfare conditions. We also use cultured chicken cells, the waxworm (Galleria melonella) insect infection model and mathematical modelling approaches which has allowed us to use fewer animals in better designed experiments but ultimately most of our work requires the complexity of the whole animal.
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