Lawsonia intracellularis: getting inside the pathogenesis of proliferativeenteropathy

Although proliferative enteropathy (PE) has been recognised for several dec ades, Lawsonia intracellularis, the aetiological agent, was identified form ally in only 1995. This organism is both highly fastidious and obligately i ntracellular bacterium, characteristics which have inevitably restricted in vestigations in all aspects of its biology. Despite these limitations, adva nces have been made in characterising and understanding L. intracellularis- host interaction both in vivo and in vitro. Based upon evidence provided by mainly pathological and histological investigations conducted to date, we review salient features of our current understanding of processes involved throughout the course of infection by this unique pathogen. (C) 2001 Elsevi er Science B.V. All rights reserved.