PERSISTENCE OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS INSERUM AND SEMEN OF ADULT BOARS

Four seronegative-adult boars were intranasally inoculated with porcin e reproductive and respiratory syndrome virus (PRRSV) isolate VR-2332. Serum and semen were collected 2-3 times weekly for over 100 days pos tinoculation (DPI). Serum samples were assayed for PRRSV by virus isol ation (VI) and a polymerase chain reaction (PCR) and screened for anti bodies to PRRSV using the indirect fluorescent antibody (IFA) and viru s neutralization (VN) tests. Semen was assayed for PRRSV RNA by PCR. V irus or viral RNA was detected in the serum of all boars within 1 DPI by VI and/or PCR. However, VI results indicated that viremia was trans ient and occurred from 1 to 9 DPI. Viral RNA was detected in serum fro m 1 to 31 DPI. In the acute stage of the infection, PRRSV RNA was dete cted in serum by PCR prior to the presence of viral RNA in semen. The PRRSV RNA was detected in semen as early as 3 DPI and persisted for 25 DPI in 2 of the boars and 56 and 92 DPI in the remaining 2 boars. Det ection of PRRSV RNA in semen occurred 2-8 and 28-35 days prior to the detection of antibodies by IFA and VN, respectively. PRRSV was isolate d from the bulbourethral gland of the boar that shed viral RNA in seme n for 92 DPI. These results suggest that PRRSV RNA can be detected by PCR in boar serum and semen, and may persist for variable periods of t ime; Viremia and the serologic status of the boar are not adequate ind icators of when PRRSV or PRRSV RNA is being shed in the semen. Prelimi nary findings also indicated that neither shipping stress nor reinocul ation with homologous PRRSV resulted in viremia or viral RNA shedding in semen.