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Evaluation of protective immunity in pigs following oral administration of an avirulent live vaccine of Lawsonia intracellularis

Jeremy J. KrollDepartment of Biological Research and Development, Boehringer Ingelheim Vetmedica Inc, 2501 N Loop Dr, Ames, IA 50010.

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Michael B. RoofDepartment of Biological Research and Development, Boehringer Ingelheim Vetmedica Inc, 2501 N Loop Dr, Ames, IA 50010.

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Steven McOristDepartment of Clinical Development, QAF Meats, Bunge, Australia.

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 BVSc, PhD

Abstract

Objective—To evaluate the efficacy of an orally administered avirulent live vaccine to protect pigs against challenge exposure with virulent Lawsonia intracellularis.

Animals—108 weaned 3-week-old pigs (35 in experiment 1 and 73 in experiment 2).

Procedure—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 107.7 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 and Clinical Relevance—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. ( Am J Vet Res 2004;65:559–565)

Abstract

Objective—To evaluate the efficacy of an orally administered avirulent live vaccine to protect pigs against challenge exposure with virulent Lawsonia intracellularis.

Animals—108 weaned 3-week-old pigs (35 in experiment 1 and 73 in experiment 2).

Procedure—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 107.7 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 and Clinical Relevance—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. ( Am J Vet Res 2004;65:559–565)