Sabrina L. Swenson, DVM, PhD; Howard T. Hill, DVM, PhD; Jeff J. Zimmerman, DVM, PhD; Lawrence E. Evans, DVM, PhD; Robert W. Wills, MS, DVM; Kyoung-Jin Yoon, DVM, PhD; Kent J
Seven boars serologically negative to porcine reproductive and respiratory syndrome virus (PRRSV)) were inoculated intranasally with PRRSV; four were vaccinated with PRRSV vaccine while the other three served as nonvaccinated controls. Semen samples were collected twice weekly for 32 days to determine the effect of the vaccine on PRRSV shedding in the 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 PRRSV in 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 PRRSV with the use of an inactivated PRRSV vaccine.