The present invention provides nucleic acid and amino acid sequences useful as the immunogenic portion of vaccines or immunogenic compositions effective for lessening the severity of the clinical symptoms associated with Lawsonia intracellularis infection or conferring protective immunity to an animal susceptible to such infection. Preferred amino acid sequences are selected from the group consisting of 1) a polypeptide comprising a sequence selected from the group consisting of SEQ ID Nos.: 1-455, SEQ ID No 466, or the polypeptide encoded by SEQ ID No: 456, SEQ ID No: 457 or SEQ ID No: 466; 2) any polypeptide that has at least 85% sequence homology, more preferably at least about 90% sequence homology, still more preferably at least about 95% sequence homology, even more preferably at least about 97% sequence homology, still even more preferably at least about 98% sequence homology, and even more preferably at least about 99% sequence homology to the polypeptide of 1); 3) any immunogenic portion of the polypeptides of 1) and/or 2) 4) the immunogenic portion of 3), comprising at least 300, 290, 280, 270, 260, 250, 240, 230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 18, 15, 13, 10, or most preferably 9 contiguous amino acids included in the sequences of SEQ ID No: 1-455, SEQ ID No: 456, or the amino acid sequence encoded by SEQ ID No: 457 or SEQ ID No: 466; and/or 5) a polypeptide that is encoded by a DNA that codes for a peptide comprising the sequence of SEQ ID No: 1-455 or SEQ ID No: 466. Thus, the nucleic acid sequences encoding such proteins, or the proteins themselves are included in vaccine compositions, together with veterinary-acceptable carrier and administered to an animal in need thereof.