Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346 León, Spain.
Vet Res. 2014 Jan 29;45(1):9. doi: 10.1186/1297-9716-45-9.
After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.
在妊娠中期，给母羊口服 2000 个新鲜制备的弓形虫分离株 M4 的孢子化卵囊后，91.6%感染和怀孕的母羊在第 7 至 11 天发生流产。之后，在另一组绵羊中进行了晚期妊娠感染，用 500 个孢子化卵囊进行感染。在感染的母羊中，又有 58.3%在感染后第 9 至 11 天发生流产。在自然和实验性绵羊弓形体病中，经典的流产通常发生在感染后一个月。少数实验研究报告了所谓的急性流产，即在口服接种卵囊后 7 至 14 天就发生流产，发热被认为是导致流产的原因，尽管其潜在机制尚未阐明。在本研究中，所有来自急性流产母羊的胎盘分析显示，胎盘胎盘中的绒毛和血栓梗死和缺血性病变（脑室周围白质软化）在一些胎儿的大脑中。通过 PCR 在只有一只绵羊的一些胎盘样本中鉴定出寄生虫，并且通过免疫组织化学标记未检测到抗原。这些发现表明，胎盘中发现的血管病变以及胎儿缺氧损伤可能与急性流产的发生有关。尽管这些病变的发病机制仍有待确定，但分离株的感染剂量或毒力可能在其发展中起作用。
