College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, China.
Department of Microbiology, University of Tennessee, Knoxville, USA.
Int J Food Microbiol. 2020 Jun 2;322:108563. doi: 10.1016/j.ijfoodmicro.2020.108563. Epub 2020 Feb 19.
Toxoplasmosis is one of the most common foodborne diseases in the world. The objective of this study was to determine Toxoplasma gondii infection in lambs from Henan province, China. A total of 166 lamb hearts were collected from 2017 to 2019. T. gondii infection was determined by the Modified Agglutination Test (MAT) using heart juice of lambs. 11 isolates (TgSheepCHn3 - TgSheepCHn13) were obtained from samples with MAT titers ≥1:100. The rate of T. gondii isolation increased with antibody titer against T. gondii (P < 0.05). No isolate was obtained from samples with titer 1:25 and 1:50, suggesting the cut-off titer for MAT is better set at 1:100. With cut-off value of 1:100, IgG antibodies to T. gondii were found in 25.3% (42/166) of the lambs by MAT. T. gondii parasite was not found in IHC and HE-stained tissue sections of lamb hearts (0/166). Sixty-seven heart tissues with ≥1:25 MAT titers were subjected to acid pepsin digestion and detected T. gondii by PCR. Only 7.5% (5/67) of DNA amplified products were found in heart tissues by the primer TOX5/TOX8. Brain tissue cysts were observed in all mice infected with the 11 isolates at day 60 post infection, suggesting these isolates are non-lethal to mice. PCR-RFLP analysis revealed that 7 isolates belonged to ToxoDB#2, 4 isolates belonged to ToxoDB#4. This is the first isolation of ToxoDB#2 and ToxoDB#4 from lambs in China. Interestingly, none of these isolates belongs to the ToxoDB#9 that is common in China. Our results suggest that the genetic diversity and population structure of T. gondii from China maybe more abundant and magical than previous speculation.
弓形虫病是世界上最常见的食源性疾病之一。本研究旨在确定中国河南省绵羊中的弓形虫感染情况。从 2017 年至 2019 年共采集了 166 只羔羊的心脏。通过使用羔羊的心脏汁液进行改良凝集试验（MAT）来确定 T. gondii 感染。从 MAT 滴度≥1：100 的样品中获得了 11 个分离株（TgSheepCHn3-TgSheepCHn13）。随着抗 T. gondii 抗体滴度的增加，T. gondii 分离率也增加（P<0.05）。在滴度为 1：25 和 1：50 的样品中未获得分离株，这表明 MAT 的截止滴度更好地设定在 1：100。使用 1：100 的截止值，通过 MAT 在 25.3％（42/166）的羔羊中发现了针对 T. gondii 的 IgG 抗体。在羔羊心脏的 IHC 和 HE 染色组织切片中未发现 T. gondii 寄生虫（0/166）。对 67 个 MAT 滴度≥1：25 的心脏组织进行酸胃蛋白酶消化，并通过 PCR 检测 T. gondii。仅在心脏组织中发现 7.5％（5/67）的引物 TOX5/TOX8 扩增产物。在感染后第 60 天，所有感染 11 个分离株的小鼠均观察到脑组织囊肿，表明这些分离株对小鼠无致死性。PCR-RFLP 分析显示，7 个分离株属于 ToxoDB#2，4 个分离株属于 ToxoDB#4。这是中国首次从羔羊中分离出 ToxoDB#2 和 ToxoDB#4。有趣的是，这些分离株中没有一个属于中国常见的 ToxoDB#9。我们的研究结果表明，中国 T. gondii 的遗传多样性和种群结构可能比以前的推测更为丰富和神奇。
