Campylobacter jejuni in Poultry: A Commensal or a Pathogen?

Campylobacter has a long standing association with poultry and is the main cause of cases of human foodborne disease in the developed world, with most cases being linked back to the poultry reservoir, particularly chicken. Campylobacter is ideally suited to the poultry niche, and can grow at the increased body temperature of birds of 42 °C. Historically Campylobacter was referred to as a commensal of poultry, as it is found in the majority of birds reared for human consumption irrespective of the breed or rearing system used, even though there is experimental evidence from over 30 years ago that certain Campylobacter strains harm broiler chickens. More recently there is an increasing body of evidence, supporting this early work, which indicates that Campylobacter is not necessarily a commensal of poultry and under certain conditions the bacterium behaves more like a pathogen. Birds mount innate and adaptive immune responses to Campylobacter. Recent studies have highlighted the ability of Campylobacter to leave the gut and be found in other internal organs and muscle tissue. In addition, Campylobacter has been shown to have a negative effect on the health and welfare of the birds, Furthermore evidence of host adaptation and host-specific species leads us to believe that Campylobacter is more than just a commensal of chickens. Here we will review the role of Campylobacter, host adaption and commensalism within the poultry niche.