The use of a whole inactivated PRRS virus vaccine administered in sows and impact on maternally derived immunity and timing of PRRS virus infection in piglets.

Background: Porcine reproductive and respiratory syndrome virus (PRRSV) vaccination is usually based on administering periodically PRRS modified live virus (MLV) in sows throughout their life. Using this schedule, transfer of maternally derived antibodies to the offspring is limited. The aim of the present study was to test the concept of priming with an MLV and boosting with a commercial inactivated virus vaccine in sows to reduce PRRSV incidence and improve productivity.

Methods: On two farms, all the sows were vaccinated with a MLV vaccine at week 8 of gestation. Then two groups were designated, one group was re-vaccinated in the third week prior to farrowing and using a commercial inactivated vaccine (the PG group). The second group was the control group (C). Assays for PRRSV infection and productive parameters were evaluated.

Results: For both farms, the incidence of PRRSV was lower at 6 weeks of age in PG than in C (p < 0.05). At weaning the proportion of PRRSV seropositive piglets was higher for PG as well (p < 0.05). The litters from C sows from both farms showed a higher pre-weaning mortality (odds ratio, C vs. PG = 1.18 ± 0.09; p < 0.05).

Conclusions: Administration of the vaccine in sows before farrowing was safe and associated with reduced incidence of PRRSV in piglets up to 6 weeks of age.