Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
Vet Parasitol. 2013 Feb 18;192(1-3):129-36. doi: 10.1016/j.vetpar.2012.09.037. Epub 2012 Oct 8.
Sheep are commonly infected with the protozoan parasite, Toxoplasma gondii. Infection may cause early embryonic death and resorption, fetal death and mummification, abortion, stillbirth, and neonatal death. Most sheep acquire T. gondii infection after birth. Recent studies reported that congenital ovine transmission of T. gondii may be more common than previously believed, but these findings are solely based on PCR data and require confirmation using other techniques to verify the findings. In the present study, during the lambing season of 2005 a toxoplasmosis abortion storm occurred in a flock of purebred Suffolk ewes on a farm in Texas. Only 14 healthy lambs were born, and 38 abortuses, mummies and weak or stillborn lambs were delivered. Another 15 fetuses identified by ultrasound were presumably resorbed or were aborted undetected. Antibodies to T. gondii were found in 37 (94.8%) of the 39 ewes and 30 of them had high titers (1:3200 or higher) when tested in the modified agglutination test (MAT). In the 2006 lambing season, two (both with MAT titers of ≥ 3200 in 2005) of 26 ewes delivered T. gondii infected lambs. T. gondii tissue cysts were found histologically in lesions of encephalitis in a lamb from one ewe and viable T. gondii (designated TgShUs55) was isolated from the brain and heart of a lamb from the second ewe. TheTgShUs55 had an atypical genotype using 10 PCR-RFLP markers, and was 100% lethal for Swiss Webster mice, irrespective of the dose or the stage of the parasite inoculated. In subsequent seasons, the ewes lambed normally. The results of the present study support the hypothesis that most sheep that have aborted due to T. gondii develop protection against future toxoplasmosis induced abortion, but the protection is not absolute.
绵羊通常会感染原虫寄生虫弓形虫。感染可能导致早期胚胎死亡和吸收、胎儿死亡和木乃伊化、流产、死产和新生儿死亡。大多数绵羊在出生后获得弓形虫感染。最近的研究报告称，先天性绵羊弓形虫传播可能比以前认为的更为常见，但这些发现仅基于 PCR 数据，需要使用其他技术来验证这些发现。在本研究中，在 2005 年的产羔季节，德克萨斯州一个农场的纯种萨福克母羊群中发生了一场弓形虫流产风暴。仅产下 14 只健康羔羊，产下 38 只流产、木乃伊和虚弱或死产羔羊。另外 15 只通过超声确定的胎儿被认为是吸收或未被检测到的流产。在 39 只母羊中发现了 37 只（94.8%）抗弓形虫抗体，其中 30 只在改良凝集试验（MAT）中检测到高滴度（1:3200 或更高）。在 2006 年的产羔季节，26 只母羊中有 2 只（2005 年 MAT 滴度均≥3200）产下了弓形虫感染的羔羊。从一只母羊的脑炎病变中发现了弓形虫组织囊肿，从第二只母羊的大脑和心脏中分离出了活的弓形虫（命名为 TgShUs55）。TgShUs55 使用 10 个 PCR-RFLP 标记物具有非典型基因型，对瑞士 Webster 小鼠具有 100%的致死性，与寄生虫接种的剂量或阶段无关。在随后的季节中，母羊正常产羔。本研究的结果支持这样的假设，即大多数因弓形虫而流产的绵羊会对未来的弓形虫诱导性流产产生保护，但这种保护并非绝对。
