GHENT UNIVERSITY

1. GHENT UNIVERSITY Department of Veterinary Public Health and Food Safety, Department of Reproduction, Obstetrics, and Herd Health Faculty of Veterinary Medicine, Ghent University DISTRIBUTION OF SALMONELLA STRAINS IN FARROW-TO-FINISH HERDS: A LONGITUDINAL STUDY Nollet N., Houf K., Dewulf J., Duchateau L., De Zutter L., de Kruif A., Maes D. Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium • AIMS OF THE STUDY • To elucidate time points with higher probability for Salmonella excretion in pigs from weaning until slaughter • To investigate the distribution of different Salmonella strains within farrow-to-finish herds MATERIALS AND METHODS • Study population: • 34, 40 and 32 sows in herd A, B and C, resp. • 3 randomly selected piglets per sow  102, 120 and 96 piglets in herd A, B and C, resp. • Collection of faecal samples: • Sows: late gestation (n=3), lactation (n=3), post-weaning (n=3) • Pigs: lactation (n=1), nursery (n=3), growing (n=3), finishing (n=3) • Collection of samples post-slaughter: • Jejunum content, colon content, mesenteric lymph nodes • Sample analyses: • Qualitative Salmonella isolation (BPW, MSRV, XLD, biochemical confirmation) • RAPD, PFGE, serotyping • Statistical analyses: • McNemar test: proportion of excretors before and after moving • Chi-square test: proportion of excretors at the herd and the proportion of positive animals after slaughter RESULTS Faecal samples before slaughter and samples collected post-slaughter Faecal samples: Salmonella excretion in pigs from weaning until slaughter Distribution of Salmonella strains within 3 farrow-to-finish herds1 1The number of strains isolated during the different periods and at the slaughterhouse. The strains were serotyped as S. Infantis (I), S. Goldcoast (G), S. Derby (D), S. Typhimurium (T); S. Livingstone (L), S. Brandenburg (B), S. London (Lo), S. Nagoya (N). Different strains were given a different number within a herd. • DISCUSSION AND CONCLUSION • Salmonella shedding started after weaning, peaked during the first half of the finishing period followed by a decline to undetectable levels. This is similar to other studies (Funk et al., 2001; Beloeil et al., 2003; Kranker et al., 2003). • Significant increases were observed after transferring to a new unit. Salmonella shedding is probably triggered by stress due to moving, transport, commingling, change of feed,.... (Berends et al., 1996; Roth, 1999) and was followed by horizontal transmission. • The strains found during nursery, growing and finishing period were closely related or identical to the strains isolated in the sows or in the environment. Also new strains were found. • After transport to the slaughterhouse Salmonella carriers re-started shedding (Berends et al., 1996). • The strains found in the jejunum content were partly identical to those isolated at the herd, other strains were new. All but one strain recovered from colon content and from mesenteric lymph nodes were identical to those found at the herd. • Based on the distribution of the different strains, indirect transmission of Salmonella between different units in a herd is of great importance Cited references can be obtained from the first author