title: Evaluation of protective immunity in pigs following oral administration of an avirulent live vaccine of Lawsonia intracellularis.
abstract: OBJECTIVE
  To evaluate the efficacy of an orally administered avirulent live vaccine to protect pigs against challenge exposure with virulent Lawsonia intracellularis.
  
  
  METHODS
  108 weaned 3-week-old pigs (35 in experiment 1 and 73 in experiment 2).
  
  
  METHODS
  2 experiments were conducted. On day 0, vaccinates were orally administered vaccine via drench or in drinking water, whereas challenge-control pigs were administered cultured medium. On day 21, pigs were challenge exposed with a virulent heterologous isolate of L. intracellularis. Clinical observations, weights, seroconversion, and fecal excretion of L. intracellularis were measured until day 42. At study termination, pigs were euthanatized and examined for L. intracellularis-specific lesion development of the ileum and colon.
  
  
  RESULTS
  Pigs receiving a single dose of vaccine were protected when challenge exposed with virulent L. intracellularis (at least 10(77) TCID50/dose). In experiment 1, vaccinates had significantly less fecal excretion (47% and 40% for days 35 and 42, respectively), compared with challenge-control pigs. In experiment 2, vaccinates had significantly less fecal excretion (50% and 58% for days 35 and 42, respectively), compared with challenge-control pigs. Significant reductions in lesion development were evident in the ileum of vaccinated pigs (70% and 56% at day 42 for experiments 1 and 2, respectively), compared with challenge-control pigs.
  
  
  CONCLUSIONS
  Oral administration by drench or via drinking water of an avirulent live vaccine against L. intracellularis resulted in substantial protection against proliferative enteropathy among vaccinates and offers a better way to reduce stress of pigs during vaccine administration.
authors.affiliation: Department of Biological Research and Development, Boehringer Ingelheim Vetmedica Inc, 2501 N Loop Dr, Ames, IA 50010, USA.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Kroll
authors.forename: Michael B
authors.initials: MB
authors.lastname: Roof
authors.forename: Steven
authors.initials: S
authors.lastname: McOrist
mesh_terms: D000284:Administration, Oral; D000704:Analysis of Variance; D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000276:immunology*; D003106:Colon / Q000473:pathology; D045824:Desulfovibrionaceae Infections / Q000276:immunology / Q000662:veterinary*; D023381:Endpoint Determination; D005243:Feces / Q000382:microbiology; D005455:Fluorescent Antibody Technique; D007082:Ileum / Q000473:pathology; D007150:Immunohistochemistry; D007410:Intestinal Diseases / Q000276:immunology / Q000473:pathology / Q000662:veterinary*; D020639:Lawsonia Bacteria / Q000276:immunology*; D034421:Sus scrofa; D013553:Swine Diseases / Q000276:immunology* / Q000382:microbiology
chemical_list: D001428:Bacterial Vaccines