Assessment of factors influencing the within-batch seroprevalence of human enteropathogenic Yersinia spp. of pigs at slaughter age and the analogy with microbiology.

The microbiologically and serologically-based prevalence of human enteropathogenic Yersinia spp. at moment of slaughter varies between pig farms due to different herd-level factors. A face-to-face questionnaire concerning a broad range of farm aspects (e.g., management and housing system, biosecurity, and hygiene measurements) was performed on one hundred farms. Factors influencing the seropositivity of 7047 pigs against human pathogenic Yersinia spp. were determined and compared to the microbiology. At the slaughterhouse, pieces of diafragm of on average 70 slaughter pigs per batch were sampled to determine the level of antibodies against enteropathogenic Yersinia spp. After univariable mixed-effect logistic regressions, variables that were related to the seropositivity (p<0.05) were included in a multivariable model (p<0.1). The factors remaining significantly associated in the latter model were an increasing number of piglet suppliers (zero up to eleven suppliers) (Odds Ratio=1.4), a high density of pig farms in the area (high versus low density) (Odds Ratio=2.3), the use of semislatted floors in the fattening pig unit (semi slatted floor versus fully slatted floor) (Odds Ratio=3.8) and the possibility of snout contact in the fattening pig unit (snout contact or not) (Odds Ratio=0.1). Decreasing the risk of infection with human enteropathogenic Yersinia spp. at moment of slaughter or during rearing is possible by changing farm management factors.