An evaluation of the immune response induced by the PEDV conditional vaccine on animals that were naturally exposed to wild virus 18 months prior

The object was to determine if Zoetis’ conditionally licensed PEDV vaccine will enhance immunity in animals that were exposed to wild PEDV virus approximately 18 months prior.

This project was performed from 7/20-9/8 2015 at a 2,200 sow breed-to-wean site that broke with PEDV in February 2014. The enrolled sows farrowed in August 2015 which is approximately 18 months post-infection. The study’s protocol used only females present during the outbreak of PEDV, so parity 3 and older females were selected for the study. Enrolled females were randomly assigned to one of the following two treatment groups. Treatment group 1 was control and treatment group 2 was vaccinated with one dose two weeks pre-farrowing. Each group consisted of 30 total females. Samples were collected from at least 16 animals. The reason for fewer animals then enrolled was due to proper timing of colostrum collection. Treatment groups were bled at two weeks pre-farrow. Colostrum was collected at farrowing and milk was collected at five days post parturition. Samples were tested at South Dakota State University for the FFN/serum neutralization test. Treatment groups were evenly distributed over two “breeding” weeks due to a decision by the farm’s owner to insert a higher percentage of replacement gilts.

The presence of PEDV was not detected on routine tissue and rectal swab submissions prior to starting the trial. The objective was to make sure an endemic situation was not present. The conditional PEDV vaccine had been utilized in the sow herd since November 2014 as a single dose prefarrowing. The females enrolled into the trial had been vaccinated with the vaccine prior to each previous farrowing with the last vaccination approximately four month previously. Four different charts will illustrate the outcomes of this study. One chart shows the baseline serum neutralizing antibody statue prior to vaccination. A second chart will illustrate treatment 2 response in serum antibodies compared to non-vaccinates. A third chart will illustrate no difference between vaccinates and non-vaccinates in neutralizing antibodies in colostrum, although both groups had high titers. A final chart will show higher and more uniform neutralizing antibody titers in milk samples.

In conclusion animals that had experienced wild virus exposure even up to 18 months prior, the use of the Zoetis conditional PEDV at two weeks pre-farrowing, resulted in a two-fold serologic response at the time of farrowing and resulted in higher and more uniform neutralizing antibody titers in milk (lactogenic immunity).

Disclosure of Interest: None Declared.