Evaluation of the humoral immune response and fecal shedding in weanling foals following oral and intra-rectal administration of an avirulent live vaccine of Lawsonia intracellularis

• Published in: The veterinary journal (1997) 2009-12, Vol.182 (3), p.458-462
• Main Authors: Pusterla, Nicola, Hilton, Hugo, Wattanaphansak, Suphot, Collier, Jessica R., Mapes, Samantha M., Stenbom, Robert M., Gebhart, Connie
• Format: Article
• Language: English
• Subjects: Administration, Oral; Administration, Rectal; Animals; Animals, Newborn; bacterial infections; Bacterial Vaccines - administration & dosage; Desulfovibrionaceae Infections - immunology; Desulfovibrionaceae Infections - prevention & control; Desulfovibrionaceae Infections - veterinary; digestive system; disease prevention; drug delivery systems; Enteritis - immunology; Enteritis - microbiology; Enteritis - prevention & control; Enteritis - veterinary; feces; Feces - microbiology; Female; Foals; horse diseases; Horse Diseases - immunology; Horse Diseases - microbiology; Horse Diseases - prevention & control; Horses; humoral immunity; immune response; Immunity, Humoral; immunologic techniques; intra-rectal administration; Intra-rectal vaccine; Lawsonia Bacteria - immunology; Lawsonia intracellularis; live vaccines; Male; Modified-live vaccine; oral administration; Oral vaccine; pathogen shedding; polymerase chain reaction; vaccination; Vaccines, Attenuated; weanlings
• ISSN: 1090-0233; 1532-2971
• DOI: 10.1016/j.tvjl.2008.08.016

Equine proliferative enteropathy (EPE) caused by Lawsonia intracellularis has recently been recognized as an emerging disease in foals. Whilst the clinical entity, diagnostic evaluation and treatment of affected foals have been well established and described, preventive measures for EPE have remained largely unaddressed. The objectives of this study were to investigate the humoral immune response and onset and duration of fecal shedding in foals after oral and intra-rectal administration of a modified-live vaccine of L. intracellularis. Foals were vaccinated twice, 3 weeks apart, via oral drenching after pre-medication with a proton-pump inhibitor (omeprazole; group 1), intra-rectally (group 2) or orally without any pre-medication (group 3). The health status of the foals was monitored daily, with feces and serum collected at regular intervals for Polymerase Chain Reaction (PCR) and serology. All foals remained healthy and no adverse vaccine reactions were observed. Fecal shedding lasted from 1 to 12 days and was mainly detected in foals receiving the intra-rectal vaccine 11–15 days following the first vaccine administration. Serological responses were measured in the majority of the vaccinated foals. All foals vaccinated intra-rectally seroconverted after the first vaccine, compared to 50% and 0% of foals in groups 1 and 3, respectively. Pre-medication with omeprazole prior to oral vaccination in group 1 foals led to an earlier and stronger detectable humoral response compared to non pre-medicated foals.