Salmonella in sows: a longitudinal study in farrow-to-finish pig herds Nathalie Nollet, Kurt Houf, Jeroen Dewulf, Aart De Kruif, Lieven De Zutter and Dominiek Maes Vet. Res., 36 4 (2005) 645-656 DOI: 10.1051/vetres:2005022