Effect of gilt seropositivity to Lawsonia intracellularis (LI) on their offspring's seropositivity to LI and on diarrhoea after a pure-culture challenge.

This study was done in a large Croatian pig-production unit. Blood samples from late-pregnancy gilts were tested by an indirect immunofluorescence-antibody (IFA) serum assay for Lawsonia intracellularis (LI). Ten IFA-positive and 10 IFA-negative gilts were selected. The 2-week-old piglets (97 from positive gilts, and 98 from negative gilts) were inoculated intragastrically with pure culture of LI. All pigs were tested until slaughter for seroprevalence of LI. Blood samples were collected at 5, 8, 11, 14, 17, 20, 23 and 26 weeks of age. Seropositivity in offspring of IFA-negative gilts was highest at age 5 weeks (84%) and declined gradually from week 11 to only 10% at week 26. At the same time, the offspring of IFA-positive gilts showed lower and faster-decaying seroprevalence: only 32% at week 5 and 0% starting at week 17. There was no difference in the pen-days of diarrhoea between the offspring of LI-seropositive and -seronegative gilts.