Schelkopf Adam, Nerem Joel, Cowles Bobby, Amodie Deb, Swalla Richard, Dee Scott
Pipestone Veterinary Clinic, 1300 S. Highway 75, Pipestone, MN 56164, USA.
Outcomes Research, Zoetis Inc, 100 Campus Drive, Florham Park, NJ 07932, USA.
Vaccine. 2014 Aug 6;32(36):4639-43. doi: 10.1016/j.vaccine.2014.06.073. Epub 2014 Jun 24.
The study evaluated the safety of a modified live-virus (MLV) porcine reproductive and respiratory syndrome (PRRS) vaccine in susceptible, pregnant gilts. To simulate inadvertent exposure secondary to postvaccination shedding of PRRS-MLV, seronegative gilts (n=51) were exposed by IM vaccination at 90 days of gestation. Vaccinated and nonvaccinated, seronegative control gilts (n=25) were maintained in separate facilities. The PRRS-MLV vaccine was given in a 2mL dose on day 0. On day 7 all vaccinated gilts were PRRSV-PCR-positive for PRRSV and had responded serologically as determined by an ELISA. All control gilts remained PRRSV-PCR- and ELISA-negative throughout the study. Abortions did not occur in gilts from either group. The difference between vaccinated and control gilts in average number of piglets per litter (12.43 and 12.16, respectively), number of live births per litter (11.21 and 11.54), and mean piglet birth weight (3.22 and 3.26 lbs) were not significantly different. Piglets in the control group had significantly greater average daily gain versus piglets from vaccinated gilts (0.52 vs. 0.46 lbs, P<0.0001). Preweaning mortality was significantly greater (P=0.0023) in piglets from the vaccinated gilts (19.7% vs. 10.9%). A single gilt accounted for 18.2% of stillbirths in the vaccinated group. Air samples were borderline PRRSV-PCR-positive for PRRSV on days 29 and 32, after more than 98% of gilts had farrowed. Results demonstrated that vaccination of pregnant gilts at the time of peak fetal susceptibility was non-abortigenic and that the PRRS-MLV agent did not significantly affect reproductive outcomes. Lower ADG in piglets from vaccinated gilts may be due to PRRS-MLV viremia following transplacental or post-farrowing exposure. Air sampling results indicated that environmental contamination with PRRS-MLV shed from vaccinated gilts was minimal.
该研究评估了一种改良活病毒（MLV）猪繁殖与呼吸综合征（PRRS）疫苗在易感怀孕后备母猪中的安全性。为模拟接种PRRS-MLV疫苗后病毒排出导致的意外暴露，在妊娠90天时对血清学阴性的后备母猪（n = 51）进行肌肉注射接种。接种疫苗的血清学阴性后备母猪（n = 25）和未接种疫苗的血清学阴性对照后备母猪被安置在不同的设施中。PRRS-MLV疫苗在第0天以2mL剂量接种。在第7天，所有接种疫苗的后备母猪PRRSV-PCR检测呈PRRSV阳性，并且通过ELISA检测血清学有反应。在整个研究过程中，所有对照后备母猪PRRSV-PCR和ELISA检测均为阴性。两组后备母猪均未发生流产。接种疫苗的后备母猪与对照后备母猪每窝仔猪平均数量（分别为12.43和12.16）、每窝活产仔猪数量（11.21和11.54）以及仔猪平均出生体重（3.22和3.26磅）之间的差异不显著。与接种疫苗的后备母猪所产仔猪相比，对照组仔猪的平均日增重显著更高（0.52磅对0.46磅，P<0.0001）。接种疫苗的后备母猪所产仔猪的断奶前死亡率显著更高（P = 0.0023）（19.7%对10.9%）。在接种疫苗的组中，有一头后备母猪的死胎占死胎总数的18.2%。在超过98%的后备母猪产仔后，第29天和第32天的空气样本PRRSV-PCR检测呈PRRSV弱阳性。结果表明，在胎儿易感性高峰期对怀孕后备母猪进行疫苗接种不会引起流产，并且PRRS-MLV毒株不会显著影响繁殖结果。接种疫苗的后备母猪所产仔猪平均日增重较低可能是由于经胎盘或产后暴露后PRRS-MLV病毒血症所致。空气采样结果表明，接种疫苗的后备母猪排出的PRRS-MLV对环境的污染极小。
