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frequency of the virus. Thus, effective, potent adjuvants should be identified to enhance the immunogenicity and protective efficacy of extant PRRSV vaccines. Traditional adjuvants include oil/water emulsions, liposomes, microparticles, and alum, which could
humoral and cell-mediated immune responses has been described following the application of modified-live PRRSV vaccines in pigs. 23–25 Although it has been reported that vaccination with MLV provides incomplete heterologous protection against PRRSV
Abstract
Objectives
To determine whether vaccine virus is found in serum and semen of vaccinated boars, whether vaccination prevents subsequent shedding of wild-type virus after challenge exposure, and whether semen and blood variables are altered after vaccination or challenge exposure with wild-type virus, or both.
Design
Throughout the 50-day postvaccination period, serum and semen from exposed boars were evaluated for the presence of porcine reproductive and respiratory syndrome virus (PRRSV). All boars were then challenge-exposed with PRRSV isolate VR-2332 and evaluated for an additional 27 days. Semen quality variables, serostatus, and blood variables were monitored.
Animals
7 PRRSV-seronegative adult boars.
Procedure
Semen was collected 3 times weekly and evaluated by use of a nested reverse-transcriptase polymerase chain reaction for detection of PRRSV RNA. Serum was obtained weekly and evaluated by nested reverse-transcriptase polymerase chain reaction, virus isolation, and PRRSV ELISA. Semen quality variables were evaluated 3 times weekly, and CBC was performed weekly.
Results
Vaccine virus was shed in the semen of all vaccinated boars, but shedding was of shorter duration in 4 of 5 vaccinated boars than that generally observed after exposure to wild-type virus. After challenge exposure, shedding of wild-type virus in semen was shortened or eliminated in 4 of 5 vaccinated boars. Percentage of forward movement and normal spermatozoal morphology and motility were significantly reduced in vaccinated boars after challenge exposure.
Conclusions
Vaccine virus was shed in semen of vaccinated boars, but vaccination generally reduced or eliminated shedding of wild-type PRRSV after challenge exposure. Semen quality appeared to be less than optimal, particularly after vaccination and subsequent challenge exposure with wild-type virus.
Clinical Relevance
Extra-label use of the PRRSV vaccine in boars remains controversial because some boars may still shed wild-type virus in semen after challenge exposure at postvaccination day 50. Semen quality also appeared to be altered after vaccination and subsequent challenge exposure. (Am J Vet Res 1997;58:40–45)
Abstract
Objective
To determine the safety and efficacy of vaccination of pregnant gilts with an attenuated strain of porcine reproductive and respiratory syndrome virus (PRRSV).
Animals
16 pregnant gilts.
Procedure
Pregnant gilts free of antibodies for PRRSV were assigned (4 gilts/group) to the following groups: group I, untreated controls; group II, vaccinated on day 60 of gestation; group III, vaccinated on day 60 of gestation and exposed to virulent PRRSV on day 90 of gestation; and group IV, exposed to virulent PRRSV on day 90 of gestation. Safety and efficacy of vaccination was evaluated by group comparisons of prenatal and postnatal survival of fetuses and pigs, respectively, and by the condition and rate of weight gain of liveborn pigs.
Results
Collective (prenatal and postnatal) death losses up to day 15 after farrowing (conclusion of study) were similar for groups I (7/47, 14.9%) and II (7/44, 16.9%) but were greater for group III (18/49, 36.7%) and were greater still for group IV (23/37, 62.2%). Mean body weight 15 days after farrowing was greatest for pigs in litters of group I (4.46 kg) and progressively less for the other groups (3.87, 3.76, and 2.18 kg for groups II, III, and IV, respectively).
Conclusions
Using these conditions, vaccination of gilts during midgestation appeared to be safe. However, it provided only partial protection against subsequent exposure to virulent virus.
Clinical Relevance
Attenuated-PRRSV vaccines may have to be administered to naive gilts > 30 days before conception to provide maximum protection throughout gestation. (Am J Vet Res 1999;60: 796–801)
been adopted with limited success, including use of commercial killed and modified-live PRRSV vaccines and controlled exposure of incoming female swine to farm-specific strains of PRRSV. Management practices on the farm were consistent with modern
opposed to incineration of pig carcasses), use of a live PRRSV vaccine, and weaning pigs at 21 to 27 days of age (as opposed to weaning at > 28 days of age) were risk factors for PRRSV circulation. Access of a rendering truck to a pig site as well as
.vaccine.2007.03.031 41. Linhares DCL Cano J Wetzell T , et al. Effect of modified-live porcine reproductive and respiratory syndrome virus (PRRSv) vaccine on the shedding of wild-type virus from an infected population of growing pigs . Vaccine 2012
national MSHMP PRRS incidence risk. Regarding the entry of new PRRSV variants, a new PRRSV introduction to any company breeding herd was defined in 1 of 3 ways: (1) a PRRSV recovered from swine samples that was not derived from a modified-live PRRSV vaccine
-06 16. Zuckermann FA Garcia EA Luque ID , et al. Assessment of the efficacy of commercial porcine reproductive and respiratory syndrome virus (PRRSV) vaccines based on measurement of serologic response, frequency of gamma-IFN-producing cells
University. The source of pregnant sows was a family farm that had 3 geographically separate facilities for gilt development and farrowing. Weaned pigs were vaccinated with a modified-live PRRSV vaccine and an Erysipelas bacterin. Replacement gilts were
