Evaluation of IgM, IgA, and IgG Antibody Responses Against PCV3 and PCV2 in Tissues of Aborted Fetuses from Late-Term Co-Infected Sows

Porcine circovirus type 2 (PCV2) is a ubiquitous pathogen, and co-infections with the emerging PCV3 are increasingly reported. Both PCV2 and PCV3 have been implicated in reproductive failure, yet the diagnostic criteria for PCV3 remain under development. While fetal or neonatal antibody detection is a recognized indicator of transplacental infection in multiple species, PCV2 appears to be an exception due to the possible transfer of maternal antibodies. This study evaluated IgG, IgA, and IgM antibodies in the heart, kidney, lung, and spleen of aborted fetuses from sows co-infected with PCV2 and PCV3. PCR analysis revealed that all aborted fetuses were positive for both PCV2 and PCV3, with PCV3 Ct values being generally lower than those of PCV2, although this difference was not statistically significant. Antibody profiling showed a higher prevalence of anti-PCV3 IgM and IgA compared to anti-PCV2 IgM and IgA, particularly in the heart, kidney, and lung, while IgG responses against both viruses were similar. These findings suggest that the detection of anti-PCV3 antibodies in fetal tissues may provide supportive evidence of PCV2 and PCV3 infection and the possible involvement of these viruses in reproductive failure; however, further studies are needed to establish causation definitively.