Prieto C, Suárez P, Simarro I, García C, Fernández A, Castro J M
Departamento de Patología Animal I (Sanidad Animal), Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.
Vet Microbiol. 1997 Oct 16;57(4):301-11. doi: 10.1016/s0378-1135(97)00112-0.
Twenty-five gilts without measurable porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) serum antibody titres were used for this experiment. All of them were randomly assigned to one of the treatment groups at the time of artificial insemination. Twelve gilts were exposed to PRRSV, of these, six were slaughtered on day 10 after exposure and constituted group A. The remaining six were slaughtered on day 20 after infection and constituted group C. Thirteen gilts were used as controls, six of these were slaughtered on day 10 after treatment and constituted group B. The remaining seven were slaughtered on day 20 after treatment and constituted group D. The infected gilts were inoculated with PRRSV intranasally and intravenously in the ear vein. They were observed for clinical signs of infection and the effects on conception and fertilization rates were studied, while the gilts and their embryos were tested for PRRSV and homologous antibodies. The infected animals developed signs of PRRS associated with anorexia and slight pyrexia. Infection was verified by reisolation of the virus from serum and other tissue samples and also by seroconversion. Ten out of 12 infected gilts and 10 out of 13 controls were pregnant at the time of slaughter and the ratio of embryos to corpora lutea was the same in both, infected and control groups (0.75). Therefore, infection with PRRSV at the onset of gestation did not appear to interfere with conception and fertilization rates and subsequent pregnancy. The PRRSV was not isolated from any of the embryos collected at day 10 postexposure, but was present in 20-day-old embryos of group C gilts. In this group, 60% of litters were infected prenatally, with 16% of embryos infected. The proportion of dead embryos was three times greater than in a control group D (35.4% and 9.8%, respectively). The results of this report indicate that exposure of susceptible gilts to PRRSV at the onset of gestation has no significant effect on conception and fertilization rates. However, although infection does not appear to have any effect on the embryos before implantation, it can result in transplacental infection and embryo death.
本实验使用了25头无可测猪繁殖与呼吸综合征（PRRS）病毒（PRRSV）血清抗体效价的后备母猪。在人工授精时，将它们随机分配到其中一个处理组。12头后备母猪暴露于PRRSV，其中6头在暴露后第10天被屠宰，组成A组。其余6头在感染后第20天被屠宰，组成C组。13头后备母猪用作对照，其中6头在处理后第10天被屠宰，组成B组。其余7头在处理后第20天被屠宰，组成D组。感染的后备母猪通过鼻内和耳静脉内接种PRRSV。观察它们的感染临床症状，并研究对受孕率和受精率的影响，同时对后备母猪及其胚胎进行PRRSV和同源抗体检测。感染的动物出现了与厌食和轻微发热相关的PRRS症状。通过从血清和其他组织样本中再次分离病毒以及血清转化来验证感染。12头感染的后备母猪中有10头以及13头对照中有10头在屠宰时怀孕，感染组和对照组的胚胎与黄体的比例相同（0.75）。因此，妊娠开始时感染PRRSV似乎不会干扰受孕率和受精率以及随后的妊娠。在暴露后第10天收集的任何胚胎中均未分离到PRRSV，但在C组后备母猪20日龄的胚胎中存在。在该组中，60%的窝产前感染，16%的胚胎感染。死亡胚胎的比例比对照组D高两倍（分别为35.4%和9.8%）。本报告结果表明，妊娠开始时易感后备母猪暴露于PRRSV对受孕率和受精率没有显著影响。然而，尽管感染在着床前似乎对胚胎没有任何影响，但它可导致经胎盘感染和胚胎死亡。
