Evaluating the immune response to serial administration of a conditionally licensed PEDv vaccine in naïve and previously exposed sows

Objectives

1) Determine the sow serum-neutralizing antibody titer (NABT) baseline status and response from a 2 dose blanket vaccination of Zoetis’ conditionally licensed PEDv vaccine in both a naïve population, and a farm previously exposed to PEDv.

2) Determine the NABT level expressed in colostrum and milk after triple vaccination in these farms.

A historically naïve (Farm A) and a historically PEDv positive farm (Farm B), that had experienced an acute outbreak 6 months previously and that quickly achieved negative status were used in this study. On each farm, blood samples were collected from 30 animals prior to, and 3 weeks post-double herd blanket vaccination. In addition, colostrum (within 24 hours of farrowing) and milk samples (8-14 days post-farrowing) were collected from a subset of sows that were triple vaccinated at 8, 5 and 2 weeks pre-farrow. Serum samples from Farm B were collected at the time of colostrum collection. The fluorescent focus neutralization (FFN) assay was conducted on all samples at the South Dakota State University Veterinary Diagnostic Laboratory. Any sample with NABT > 1:20 were considered positive.

Farm A:

Serum: Baseline status showed that all samples were negative. Post-double-blanket vaccination, 100% of all samples were positive with NABT ranging from 1:40-1:320.

Colostrum: All samples were positive with NABT ranging from 1:320–1:1280.

Milk: Two of 7 samples collected between 8-14 days of lactation were positive with relatively low NABT of 1:20.

Farm B:

Serum: Baseline status revealed positive NABT ranging from 1:320–1:2560 resulting from natural exposure. The NABT of most sows increased 2X after PEDv vaccination.

Colostrum: The NABT (range 1:1280-> 1:2560) were at least 2-4 times higher than in the serum (range 1:80-1:1280) of sows at the time of farrowing.

Milk: The NABT of samples collected at 4 days of lactation ranged from 1:40 to > 1:2560. Additionally, 8/9 samples collected at 21 days of lactation remained positive.

Baseline sow serum NABT in the historically positive farm were higher, and showed higher serum NABT levels post-double vaccination than the naïve farm. In addition, these results show that NABT were detected in serum and colostrum following serial vaccination in both naïve herds and herds previously exposed to PEDv.

Disclosure of Interest: T. Wolff Conflict with: Zoetis, N. Baker: None Declared, J. Baker: None Declared.