Identification of the source for salmonella contamination of carcasses in a large pig slaughterhouse

To identify the major source of Salmonella contamination in a pig slaughterhouse, samples were collected from the clean and unclean area and Salmonella isolates were further typed. Carcasses entering the clean area showed a Salmonella contamination rate of 96.7% in the oral cavity and 55.0% in the rectum content samples. Evisceration seemed not to be critical as the contamination rate of the carcasses was similar before (16.7%) and after (18.3%) this slaughter step. In the unclean area, a limited number of oral cavity samples were positive after bleeding, while a dramatic increase of positives was observed after dehairing. Salmonella was detected in up to 0.01 mL of the recycled water collected from the dehairing machine. Genotyping of Salmonella isolates showed that similar pulsotypes were present in the oral cavity and recycled water. Based on these observations it can be concluded that the recycled water used in the dehairing machine was the major source for the carcass contamination in this slaughterhouse