Lactogenic immunity following oral exposure with porcine epidemic diarrhea virus

Porcine epidemic diarrhea (PED) is a devastating enteric disease, caused by PED virus (PEDV), a RNA virus in genus Alphacoronavirus, family Coronaviridae. At present, the disease causes severe economic losses worldwide. Following an outbreak, oral administration of all sows in the herd with minced intestine (intestinal feedback) of PEDV infected pigs are suggested and the sow herd will produce healthy pigs within 2-4 weeks post exposure. The lactogenic immunity of sows following the intestinal feedback should be better understanding. Therefore, the field study was conducted to investigate the PEDV-specific lactogenic immunity of sows following oral exposure to PEDV and level of maternally derived antibody in pigs farrowing from PEDV-exposed dams.

The present study was conducted in two pig farms with inventory of 2,400 sows each, herds A and B. Herd A was a PEDV-free herd. Herd B experienced PED outbreak a year ago. Both herds were 10 kilometers away and matched in breed of sows and management system. In each herd, one hundred externally produced gilts at 22 weeks of age were introduced from a PEDV-free herd to an isolation facility of each herd. Upon arrival, one hundred gilts in herd A were orally administered with 10 grams of minced intestinal sample of piglets infected with PEDV (10⁴ TCID₅₀/ml) for 2 consecutive days, and at 12 weeks of gestation. Gilts in groups B were left as control. Colostrum and milk were collected at 7, 14 and 21 days post-farrow (DPF) and assayed for antibody by viral neutralization (VN), and ELISA IgG and IgA specific against spike protein.

The PEDV-exposed group had significantly higher VN in colostrum and milk than non-exposed group. Antibody level as measured by ELISA IgG and IgA demonstrated that sows in non-exposed group had PEDV-specific antibody titer below the cut-off level. Sows in the exposed group had numerically higher level of IgA in colostrum than that of IgA. In milk samples, IgG continuously decreased to level below cut-off level at 7 DPF and maintained at that level until 21 DPF. In contrast, IgA maintained at level above the cut-off level and significantly higher that IgG at 7-21 DPF.

The results of the study demonstrated that PED-specific IgG and IgA were detected in colostrum of sows following oral exposure with minced intestine of PEDV-infected pigs. In milk samples, however, IgA was significantly higher than IgG. This evidence suggests that the proper immunization of gilts prior to introduction into the herd should be the key.

Disclosure of Interest: None Declared.