Wild boars as an important reservoir for foodborne pathogens

One hundred fifty-three wild boars shot in the canton of Geneva, Switzerland, were studied for the occurrence of foodborne pathogens. Tonsils and fecal samples of the animals were examined using real-time polymerase chain reaction, enzyme-linked fluorescent immunoassay, and cultural methods. The detection rate of Salmonella spp., Yersinia enterocolitica, Yersinia pseudotuberculosis, stx-positive Escherichia coli, and Listeria monocytogenes was 12%, 35%, 20%, 9%, and 17%, respectively, when tonsil samples were studied. Only Y. enterocolitica (5%) and L. monocytogenes (1%) were detected in fecal samples. None of the samples was positive for Campylobacter spp. Females (71%) and young animals (61%) carried more frequently one or more pathogens than males (53%) and older ones (44%). In total, 8 Salmonella spp., 14 Y. enterocolitica, 4 Y. pseudotuberculosis, and 26 L. monocytogenes strains were further characterized. Most of the Salmonella spp. strains were of serotype Salmonella Enteritidis (75%) followed by serotypes Salmonella Stourbridge (13%) and Salmonella Veneziana (13%). L. monocytogenes strains belonged to serotypes 1/2a (42%), 1/2b (19%), and 4b (38%). Serotypes O:3 (36%), O:5,27 (21%), and O:9 (29%) were identified among Y. enterocolitica strains and serotypes O:1 (75%) and O:2 (25%) among Y. pseudotuberculosis strains. This study shows that wild boars are frequent carriers of foodborne pathogens. High wild boar densities and increasing popularity of outdoor ranging of pigs may intensify the risk of transmission of these pathogens to fattening pigs.