Estimation of the within-batch prevalence and quantification of human pathogenic Yersinia enterocolitica in pigs at slaughter

Yersiniosis is the third most common of bacterial zoonosis in the EU. The main source for human infection is pork contaminated with human pathogenic Yersinia enterocolitica, for which pigs are the primary reservoir. The aim of this study was to acquire data about the distribution of the prevalence of human pathogenic Y. enterocolitica in different batches of slaughter pigs. Between August and October 2011, in five Belgian slaughterhouses tonsils of 1397 fattening pigs, originating from 66 batches, were collected. Samples were plated onto cefsulodin-irgasan-novobiocin agar plates and suspect Yersinia colonies were enumerated. Y. enterocolitica were found in 375 pig tonsils (26.8%), originating from 46 batches. The within-batch prevalence showed a large variation between the different batches and ranged from 0 to 83.3%. In 20 batches (30.3%), no positive tonsils were detected. The average number of Y. enterocolitica was 4.04 ± 0.97 log10 CFU g−1 tonsillar tissue and the mean Yersinia count per batch varied between 3.08 and 5.89 log10 CFU g−1. In conclusion, human pathogenic Y. enterocolitica is widespread among Belgian pig farms, but there is a large variation in the within-batch prevalence among farms.