Effect of different poultry production methods on Campylobacter incidence and transmission in the broiler meat food chain

Campylobacter is the main cause of human bacterial gastroenteritis worldwide. Within the EU reported cases are rising each year. Epidemiological studies have identified that chicken meat is one of the major sources of human infection. However, it is poorly understood whether differences in chickens’ rearing and production methods impact on the contamination levels of Campylobacter on chicken meat and therefore the risk of entry into the food chain. To investigate the role of production system, flocks from diverse broiler commercial production systems with differences in welfare standards, bird type and stocking densities were investigated during the whole rearing period and at slaughter. Caecal samples were collected to estimate the flock prevalence. In order to assess the level of carcass contamination during processing, neck skin samples were collected at different production stages. Breast meat samples were also investigated to estimate the risk that chicken meat poses to human health. The objective was to link the flock Campylobacter status to the risk of contamination on the consumer’s plate. All samples were cultured for the presence of Campylobacter species. A quantitative method based on ISO 10272-2:2006, was used to determine the level of flock colonisation and Campylobacter contamination on broiler carcasses and final products. Results show that birds reared indoors under higher welfare standards with decreased stocking density with a slower growing breed (Hubbard JA57) had a reduced prevalence of Campylobacter, compared to the standard fast growing breed (Ross 308) when grown at the same stocking density. The production system with the higher Campylobacter prevalence and the higher Campylobacter count in the caecal contents, also reported a greater Campylobacter prevalence and counts on carcasses. The bacterial numbers on the final product appeared to be strongly associated with the intestinal colonisation of the slaughter batch. Consequently it is crucial to prevent flock colonisation during the rearing period, to ensure negative flocks are entering into the processing plant. The significance of the aforementioned point was also highlighted by the fact that production stages such as final washing and chilling have little impact in the reduction of contamination of the final product. The high level of contaminated carcasses showed clearly that the chicken meat is putting the UK consumers’ health at risk. An increased incidence of welfare issues, such as pododermatitis and hock lesions, was observed among the production system with the higher level of colonisation, which bring to light a link between Campylobacter colonisation and welfare issues. Furthermore, this study emphasised that stressful events such as thinning and transport were followed by an increase in Campylobacter prevalence. This highlights the importance of animal health and welfare interactions with Campylobacter spp colonisation. Multi Locus Sequence Typing (MLST) was used to determine how diverse and distinct the genetic Campylobacter population structure was among the different commercial production systems investigated. Results showed that all production systems could be potential sources of Campylobacter infection in humans with common clonal complexes found. Changes in the prevalence of genotypes associated with the final product compared to those genotypes found in birds arriving from farms were observed. This may reflect the enhanced ability of certain genotypes to resist environmental stressors, such as carcass washing, chilling, chlorine dioxide treatment and oxygen that occur during processing. In this data set, isolates belonging to the ST-257 complex showed a higher tendency to survive in the slaughterhouse environment. Internal contamination of the breast muscle was also reported in our study, hence posing a further public health threat, as the bacteria contained within the muscle are better able to survive cooking. These studies have demonstrated that this pathogen was highly prevalent among the broiler population investigated. Due to the common extent of this pathogen in food and its impact on human health, it is necessary for the Government bodies, food producers and retailers, to raise consumers’ awareness of the Campylobacter issue. Particularly the consumers must be made aware of how to manage the risk appropriately during food preparation.