Monitoring of Lawsonia intracellularis by indirect serum immunofluorescence assay in a commerical swine production system.
Steven D. Just, DVM, MS; Charles O. Thoen, DVM, PhD; Brad J. Thacker, DVM, PhD; John U. Thompson, DVM, MS
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Objectives: To determine the serological prevalence of Lawsonia intracellularis and the time of seroconversion in a commercial swine production system.
Methods: In the first phase of the study, prevalence of Lawsonia intracellularis (LI) was determined at six of approximately 150 finishing sites. Pigs were randomly selected with stratification by the source of pigs within or from outside the production system. Blood was collected from 33 to 35 pigs at each site, and serum was tested for LI antibodies by indirect immunofluorescence assay (IFA). In phase two, timing of exposure to LI was determined by IFA serum assay of 64 tagged pigs from four sow farms. Blood was first collected from suckling pigs, then at
5-weekintervals until they were sent to market (six samples per pig).
Results: Seroprevalence at the six finishing sites ranged from 0 to 54% (mean 20%). Seroprevalence was 0%, 11.4%, and 31.4% at the three Source A finishing sites; 8.5% and 14.3% at the two Source B finishing sites; and 54.3% at the outside source finishing site. In phase two, pigs seroconverted at the finishing site. Only nine of the 64 pigs tested seroconverted, and all were seronegative 5 weeks later.
Implications: Seroconversion occurred afterthe pigs entered the finishing site, suggesting exposure takes place in the nursery. As IFA titers to LI are short-lived, current and (or) previous infections may be missed when a single, cross-sectional sampling is tested.
Keywords: PPE, ileitis, Lawsonia intracellularis, indirect immunofluorescent antibody assay
Cite as: Just SD, Thoen CO, Thacker BJ, et al. Monitoring of Lawsonia intracellularis by indirect serum immunofluorescence assay in a commerical swine production system.. J Swine Health Prod 2001;9(2):57-61.
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