A commercial PCV2a-based vaccine significantly reduces PCV2b transmission in experimental conditions

Transmission characteristics of PCV2 have been compared between vaccinated and non-vaccinated pigs in experimental conditions. Twenty-four Specific Pathogen Free (SPF) piglets, vaccinated against PCV2 at 3 weeks of age (PCV2a recombinant CAP protein-based vaccine), were inoculated at 15 days post-vaccination with a PCV2b inoculum (6 ? 10⁵ TCID₅₀), and put in contact with 24 vaccinated SPF piglets during 42 days post-inoculation. Those piglets were shared in six replicates of a contact trial involving 4 inoculated piglets mingled with 4 susceptible SPF piglets. Two replicates of a similar contact trial were made with non-vaccinated pigs. Non vaccinated animals received a placebo at vaccination time and were inoculated the same way and at the same time as the vaccinated group. All the animals were monitored twice weekly using quantitative real-time PCR and ELISA for serology until 42 days post-inoculation. The frequency of infection and the PCV2 genome load in sera of the vaccinated pigs were significantly reduced compared to the non-vaccinated animals. The duration of infectiousness was significantly different between vaccinated and non-vaccinated groups (16.6 days 14.7;18.4] and 26.6 days 22.9;30.4] respectively). The transmission rate was also considerably decreased in vaccinated pigs (β = 0.09 0.05–0.14] compared to β = 0.19 0.11–0.32] in non-vaccinated pigs). This led to an estimated reproduction ratio of 1.5 95% CI 0.8 – 2.2] in vaccinated animals versus 5.1 95% CI 2.5 – 8.2] in non-vaccinated pigs when merging data of this experiment with previous trials carried out in same conditions.