On-farm multi-contamination of pigs by food-borne bacterial zoonotic hazards: an exploratory study.

Application of risk analysis to control pork-borne zoonoses on farms is a major aim of the current European food safety legislation. The prevalence, levels of contamination and variations in pig contaminations according to herds and batches must therefore be studied to define relevant methods for control of zoonoses. The aims of this exploratory study were to provide information on the prevalence and levels of infection of finisher/fattening pigs by Campylobacter spp., Clostridium perfringens, Listeria monocytogenes, Salmonella enterica and Staphylococcus aureus, and to quantify the respective effects of batches and herds. One hundred and twenty-seven pooled fresh feces samples and 120 pooled cutaneous swab samples were tested from 37 batches in 14 farrowing-to-finishing farms. Campylobacter spp. was identified in all fecal samples on farms whereas L. monocytogenes was never found. C. perfringens was identified in 48% of samples, Salmonella in 2%, and S. aureus in 48%. The decomposition of variance of on-farm prevalence and levels of contamination and a general linear model showed a systematically significant effect of herd, and an effect of batch only for levels of contamination with Campylobacter and C. perfringens and for prevalence of S. aureus. The contamination status of pigs seems to be mainly explained by herd status linked to poor biosecurity measures. Further studies are needed to explain such correlations in order to define farm indicators for food-borne zoonotic hazards.