Assessment of risk to humans related to Salmonella from bile on pig carcasses

In the European Union (EU), Salmonella is the main zoonotic hazard of interest in pig meat. Contamination occurs during slaughter mainly due to spread of faecal material. In 2020, the Danish competent authorities (CA) raised the question of the risk to humans of Salmonella resulting from bile contamination of pig carcasses. To address this, a study was undertaken involving 1) a pilot study to develop an aseptic way of collecting bile and 2) 299 gall bladder samples collected from finishing pigs from 28 pig herds. The samples were subjected to standard laboratory analysis and none were positive for Salmonella. A simulation model was set up using the collected data, plus data from the Danish meat inspection database as well as expert opinion, retrieved from the CA and the food business operator (FBO). The objective was to estimate the number of carcasses contaminated with Salmonella from bile that could be overlooked if responsibility for handling bile contamination were to rest solely with the FBO. The basic scenario showed that a median of nine (90% C.I.: 0-53) carcasses would be overlooked in a production of 16 million finishing pigs in one year, whereas 103 carcasses (90% C.I.: 7-544) would be overlooked in the worst-case scenario. Compared to the current Salmonella programme, the median relative efficacy of focusing on bile-contamination to detect Salmonella was 0.008% (basic scenario) or 0.087% (worst-case scenario). In conclusion, the risk to human health associated with Salmonella in bile on finishing pig carcasses was calculated to be negligible. Moreover, the FBO's handling of bile contamination prevents bile-contaminated carcasses from leaving the abattoir.