Dynamics of PCV2 and PCV3 in the Serum and Oral Fluids of Pigs After PCV2 Vaccination in a Commercial Farm.

Objectives: This study investigated the dynamics of porcine circovirus type 2 (PCV2) and PCV3 on a commercial farm following PCV2 vaccination.

Methods: Serum samples from 35 pigs, starting at 3 weeks of age, were collected weekly until 21 weeks of age. Oral fluids from six pens of pigs of the same age were also analyzed. Viral DNA was assessed in pooled sera and individual oral fluid samples, while antibodies (IgG and IgA) were measured in the serum and oral fluids. Productive parameters, including weekly mortality and cumulative mortality, were evaluated.

Results: The results revealed that PCV2 and PCV3 co-infection was detected in pigs at 8 weeks of age, with PCV3 being detected in oral fluids two weeks earlier. PCV3 DNA was detected in oral fluids at 4 weeks of age. PCV2 IgG antibodies in the serum increased gradually after vaccination, peaking at 7 weeks of age, then declined and stabilized until 21 weeks of age. PCV3 IgG antibodies fluctuated early but were uniformly positive after 13 weeks of age. In oral fluids, PCV2 IgG and IgA antibodies showed a strong response only at 3 and 23 weeks of age. In contrast, a strong and consistent IgG response was observed in oral fluids in the absence of PCV2 and PCV3 co-infection of pigs at 3 to 11 weeks of age. The farm's productive parameters remained stable throughout the study.

Conclusions: These findings suggest that PCV2 and PCV3 co-infection, along with high PCV3 detection levels in serum and oral fluids, may have an impact on the efficacy of PCV2 vaccination.