Comparison of vaccination protocols against Mycoplasma hyopneumoniae during the gilt acclimation period

This study evaluated different gilt vaccination protocols againstMycoplasma (M.) hyopneumoniaeat acclimationand their effect on the genetic diversity. A total of 180M. hyopneumoniaenaïve gilts were selected 1 week post-entry (wpe) at the acclimation barn in a clinically affectedM. hyopneumoniaefarm. Gilts were distributed ac-cording to theM. hyopneumoniaeantibodies levels into three different vaccination schedules: A) four doses of aM. hyopneumoniaecommercial vaccine at 2, 4, 6 and 8 wpe; B) two vaccine doses at 2 and 6 wpe and PBS at 4 and8 wpe; and C) four PBS doses at the same wpe. Detection ofM. hyopneumoniae(rt-PCR) and antibodies (ELISA)were assessed in gilts at 1, 14, 27 and 34 wpe and in 6 of their piglets at weaning. Rt-PCR positive gilts weredetected at 14 wpe, being the proportion significantly lower in groups A and B (3/120, 3%) than C (27/60, 45%).Seroconversion was detected at 14 wpe, showing significant differences in percentage of inhibition (PI) betweengroups A (median 4.9, range 3.1–19.9) and B (5.5, 3.7–13.5), and C (14.3, 3.3–53.2). Gilts remained seropositiveover the study and significant differences in PI were detected between groups A and B versus C. All piglets werert-PCR negative, but the proportion of seropositive piglets coming from vaccinated gilts was significantly higherthan the non-vaccinated group.M. hyopneumoniaecharacterization showed high variability. Hence, gilt vacci-nation with 2 or 4 doses significantly decreased the pathogen infectious pressure, variability, and provided highantibody levels to gilts and their offspring.