Dynamic Antibody Responses in Porcine Epidemic Diarrhea Virus-Infected Pigs and Correlation of Prepartum Serum, Oral Swabs, and Rectal Swabs With Postpartum Colostral IgA and IgG in Sows.

Porcine epidemic diarrhea (PED) is a highly contagious gastrointestinal disease caused by PED virus (PEDV), resulting in high mortality among neonatal piglets. Ensuring robust maternal immunity to provide protective colostral antibodies is critical for effective disease control. In this study, an enzyme-linked immunosorbent assay (ELISA) was employed to monitor antibody dynamics in PEDV-infected pigs, revealing long-term serum antibody persistence. PEDV-specific immunoglobulin (Ig)A and IgG levels were subsequently measured in prepartum serum, oral and rectal swabs, and postpartum colostrum from sows administered with different immunization strategies, including commercial vaccination and feedback. Correlations between the antibody levels in these sample types and colostrum were analyzed in order to facilitate estimation of maternal immunity and prompt adjustment of immunization programs. Results revealed that PEDV-specific IgA and IgG in piglets seroconverted 1 week after infection, peaked at two to 3 weeks, and remained detectable up to 31 weeks. Analysis of 1159 samples collected from sows at various stages across four commercial farms revealed strong correlations between serum and colostrum PEDV IgA and IgG. After the first immunization, the highest correlation coefficients for IgA and IgG were 0.6898 (p < 0.0001) and 0.5959 (p < 0.0001), respectively. After the second immunization, peak correlations reached 0.7239 (p < 0.0001) for IgA and 0.6051 (p < 0.0001) for IgG. On the day of farrowing, correlations were strongest, with IgA reaching 0.8178 (p < 0.0001) and IgG reaching 0.8682 (p < 0.0001). Additionally, oral and rectal swab IgA exhibited correlations with colostral IgA, reaching peak r values of 0.6542 (p < 0.0001) and 0.6347 (p < 0.0001), respectively, but showed minimal correlation with colostral IgG. These findings indicate that, in clinical practice, measuring PEDV-specific IgA in sow serum can provide a reliable assessment of maternal immune status and vaccine efficacy, while oral swabs and rectal swabs offer an auxiliary diagnostic avenue for supplementary evaluation. This approach facilitates earlier, more precise adjustments to immunization programs and provides a theoretical basis for optimized PEDV prevention and control strategies.