Porcine epidemic diarrhea virus (PEDV) causes a severe clinical enteric disease in suckling neonates with up to 100% mortality, resulting in devastating economic losses to the pork industry in recent years. Maternal immunity via colostrum and milk is a vital source to neonates of passive protection against diarrhea, dehydration and death caused by PEDV. Comprehensive information on neutralizing activity (NA) against PEDV in mammary secretions is critically important for assessing the protective capacity of sows. Therefore, the objectives of this study were to characterize anti-PEDV neutralizing activity in mammary secretions. Anti-PEDV NA was present in colostrum, milk and serum from PEDV-infected sows as determined both by immunofluorescence and ELISA-based neutralizing assays, with neutralization levels higher in colostrum and milk than in serum. The highest NA was observed in colostrum on day 1, and decreased rapidly in milk at day 3, then gradually declined from day 3 to day 19 post-farrowing. Notably, the NA in mammary secretions showed various patterns of decline over time of lactation that may contribute to variation in sow protective capacities. The kinetics of NA decline were associated with total IgA and IgG antibody levels. Neutralizing activity significantly correlated with specific IgA primarily to spike domain 1 (S1) and domain 2 (S2) proteins of PEDV rather than to specific IgG in colostrum. Subsequently, the NA in milk was mainly related to specific IgA to S1 and S2 during lactation.
Background In 2013, PEDV was introduced in the United States (U.S.) and rapidly spread across the country. Here we describe the occurrence of PEDV in the growing pig herd of one large U.S. production system through an active surveillance set in place between October 2019 and November 2020 designed to assess disease status upon placement into the growing pig site, before shipping to the slaughter plant and when diarrhea events were present at the site. We also assessed the impact of preventive procedures implemented in PEDV incidence that comprised site-specific equipment segregation and biosecurity changes regarding personnel movement between sites. Results 36.50% (100/274) of the sites had at least one PEDV introduction event before preventive procedures were implemented, yielding an incidence rate of 2.41 per 100 farm-weeks. Most (63/100) of them occurred in sites where animals were placed negative and PEDV was detected in clinical samples in a median of 8 weeks post placement. After preventive procedures were implemented, the overall PEDV incidence rate dropped to 0.37 per 100 farm-weeks (84.65% reduction, p < 0.001). Conclusion These results highlight the importance of systematic surveillance to identify the burden of diseases, areas of improvement in prevention and control, and to allow the measurement of the impact of policy/protocol changes.
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