UK-wide risk factor study of broiler carcases highly contaminated with Campylobacter

Campylobacter is a major cause of food poisoning and is typically the most common cause of gastroenteritis in the UK. Data collected at broiler farm and abattoir level, for slaughter batches that were sampled for UK-wide monitoring, were used to generate two epidemiological risk factor models. A total of 483 batches slaughtered between January 2016 and March 2017 were used in the analysis, coming from 19 abattoirs representing more than 85% of UK broiler production. For each selected slaughter batch, one carcase was sampled after primary chilling and 10 randomly sampled birds had caecal samples collected at the evisceration point. Samples were used for Campylobacter identification and quantification. Two multivariable mixed-effects models were designed, one with the binary outcome for the detection of a highly contaminated (>1000 colony forming units (CFU)/g) Campylobacter-positive carcase, whereas the other used the Campylobacter colony count (CFU/g) carcase outcome. The results suggest that caecal colonization within the batch was a key factor for the occurrence of Campylobacter on carcases, and many factors that were identified in the model were also likely to be related to colonization or related to the risk of introduction of Campylobacter from partial depopulation (referred to as thinning) of ~30% of the flock approximately 1 week before full flock depopulation events. The amount of neck skin in the sample was another key factor identified and was included in both models as a risk factor. The models have also identified other factors which may be related to the general health and husbandry on-farm (use of prebiotics or vaccines, and identification of the product used for drinking line cleaning), whereas the other factors may identify control points related to transmission within a farm. The identification of these variables could help focus control efforts on-farm, especially for relatively easy improvements, such as improving the provision of house-specific bird-weighing buckets/cages in houses.