Effects of porcine epidemic diarrhoea virus vaccination timing and route of administration on colostrum antibody levels and prevention of diarrhoea in piglets on a pig farm with porcine epidemic diarrhoea.

Piglets rely on passive immunity acquired from maternal-derived antibodies obtained by ingesting colostrum and milk from immunised sows. This study evaluated the differences in colostrum antibody profiles (IgA, IgG, and neutralising antibodies) according to the timing, frequency, and administration route of the porcine epidemic diarrhoea virus (PEDV) vaccination in pigs with confirmed PEDV infection, and to assess the corresponding clinical protective effects of PEDV vaccination in neonatal piglets. Piglets of sows that received two or more vaccinations, including an oral administration of a live attenuated vaccine 1 week before farrowing (3K1L and 5K3K1L groups), showed disappearance of diarrhoea and growth retardation, and exhibited a significantly higher weaning weight. Sows vaccinated with an oral live vaccine approximately 1 week before farrowing had significantly higher IgA levels than those vaccinated 2 weeks before farrowing. Neutralising antibody titres differed among the groups (p = 0.023): the thrice vaccination group (5K3K1L) showed significantly higher titres than the pre-vaccination, once (1K1L and 2K2L), and twice (3K1L) vaccination groups. IgG levels did not differ substantially between the vaccinated and unvaccinated groups. Overall, this study provides scientific evidence linking clinical protection against PEDV to antibody levels, especially IgA, in sow colostrum.