Effect of high and low levels of maternally derived antibodies on porcine circovirus type 2 (PCV2) infection dynamics and production parameters in PCV2 vaccinated pigs under field conditions

The present study aimed to compare the efficacy of a porcine circovirus type 2 (PCV2) commercial vaccine in terms of average daily weight gain (ADWG) as well as infection dynamics in pigs with different maternally derived antibody (MDA) levels. A total of 337 animals from a PCV2 subclinically infected farm were distributed into two groups based on weight and PCV2 antibody levels (high [H] or low [L]) at 2 weeks of age. One week later, these animals were subdivided in four groups according to the treatment received. Vaccinated pigs (H-V and L-V) received 1 mL of a commercial vaccine and NV (H-NV and L-NV) received 1 mL of PBS. All piglets were subsequently bled at 7, 12, 18, 22 and 25 weeks of age and weighted at 12 and 25 weeks of age. V animals showed significantly lower PCV2 infection rates and viral load as well as higher ELISA S/P ratios and ADWG than NV ones. Compared with H-V piglets, L-V pigs showed numerically lower PCV2 infection rates, lower area under the curve of viral load, an earlier seroconversion and a numerically, but not significantly, higher ADWG. In this study, MDA did not seem to interfere with the effect of PCV2 vaccination on ADWG. However, only when a small subpopulation of pigs with the highest ELISA S/P ratios at vaccination was considered, an apparent interference of vaccine efficacy on ADWG was noticed. Therefore, the impact of the putative interference under field conditions is probably negligible for most farms.

This study was funded by the European PCV2-Award 2012 sponsored by Boehringer Ingelheim. The authors wish to thank to the farmer (Álvaro Abadías) and the veterinarians (Lluís Cons and Paula Alcubierre) for their collaboration in conducting the field study and Eva Huerta, Rosa López, and Diego Pérez (CReSA) for their excellent technical assistance. Hua Feng was grant awarded by the Chinese Scholarship Council (No. 2011704032).