Preliminary assessment of an inactivated PRRS virus vaccine on the excretion of virus in semen

All boars were seropositive by indirect-fluorescent antibody (IFA)assay by.day 14 postchallenge (PC). Virus was present in semen at the time of the first collection in each of the seven boars on day 4 Pc. The two vaccinated boars that were antibody positive by the Western immunoblot assay shed PRRSVin semen for a shorter time (through days 4 and 7 PC, respectively) compared to the remaining two vaccinated boars (through days 25 and 28 PC,respectively), and the three nonvaccinated boars (through day 32 PC). Neither gross nor microscopic lesions attributable to PRRSV were observed in tissues collected at the termination of the experiment (day 32), and virus isolation attempts from reproductive tissues were negative. Results of this preliminary study suggest that it may be possible to reduce seminal shedding of PRRSVwith the use of an inactivated PRRSVvaccine.