Herd factors associated with the seroprevalences of Actinobacillus pleuropneumoniae serovars 2, 3 and 9 in slaughter pigs from farrow-to-finish pig herdsDominiek Maes, Koen Chiers, Freddy Haesebrouck, Hans Laevens, Marc Verdonck and Aart de KruifVet. Res., 32 5 (2001) 409-419DOI: https://doi.org/10.1051/vetres:2001133