Challenge virus was detected in semen collected from group 1 and 3 for a period of
up to 4 and 6 weeks after challenge, respectively. Furthermore, challenge virus was
detected in semen collected 10 days after challenge from boars vaccinated with the
live-vaccine, group 2. No challenge virus was detected in semen collected from the
previously PRRSV infected, seropositive boars of group 4