Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, National Reference Centre for Toxoplasmosis, Greifswald-Insel Riems, Germany.
Institute of Food Hygiene, Faculty of Veterinary Medicine, University Leipzig, Germany.
Int J Parasitol. 2018 Aug;48(9-10):751-762. doi: 10.1016/j.ijpara.2018.03.007. Epub 2018 May 19.
Chickens, especially if free-range, are frequently exposed to Toxoplasma gondii, and may represent an important reservoir for T. gondii. Poultry products may pose a risk to humans, when consumed undercooked. In addition, chickens are regarded as sensitive indicators for environmental contamination with T. gondii oocysts and have been used as sentinels. The aim of the present study was to determine the suitability of commonly used antibody detection methods, i.e. the modified agglutination test (MAT), IFAT and ELISA to detect T. gondii-infected chickens. Samples of experimentally and naturally infected chickens were used. The infection state of all chickens was determined by Magnetic-Capture (MC-) real-time PCR (RT PCR). Naturally exposed chickens were additionally examined by mouse bioassay and conventional RT PCR on acidic pepsin digests (PD-RT PCR). Blood serum and meat juice of various sources were tested for antibodies to T. gondii. In naturally infected chickens, there was substantial agreement between the mouse bioassay and MC-RT PCR or the mouse bioassay and conventional PD-RT PCR. PD-RT PCR was slightly more sensitive than MC-RT PCR, as all (26/26) bioassay-positive chickens also tested positive in at least one of the tissues tested (heart, drumstick). By MC-RT PCR, 92.3% (24/26) of the naturally infected bioassay-positive chickens were positive. The diagnostic sensitivity of MC-RT PCR was clearly related to the organ examined. Based on a quantitative assessment of the MC-RT PCR results in experimentally infected chickens, brain and heart tissues harbored an at least 100 times higher parasite concentration than breast, thigh or drumstick musculature. In naturally infected chickens, only three out of 24 birds, which were MC-RT PCR-positive in heart samples, also tested positive in drumstick musculature. Under experimental conditions, the agreement between MC-RT PCR and the serological techniques revealed 100% diagnostic sensitivity and specificity. Under field conditions, examinations of sera by ELISA, IFAT and MAT showed good performance in identifying chickens that were positive in either a mouse bioassay, MC-RT PCR, or PD-RT PCR as illustrated by diagnostic sensitivities of 87.5%, 87.5% and 65.2%, respectively, and diagnostic specificities of 86.2%, 82.8% and 100%, respectively. The examination of meat juice samples from breast, drumstick or heart musculature revealed similar or even better results in the ELISA. The results in the MAT with meat juice from breast musculature were less consistent than those of ELISA and IFAT because a number of negative chickens tested false-positive in the MAT. The MAT performed similar to ELISA and IFAT when applied to test meat juice samples collected from heart, thigh or drumstick musculature.
鸡，尤其是散养的鸡，经常接触刚地弓形虫，可能是刚地弓形虫的重要储存宿主。食用未煮熟的家禽产品可能对人类构成风险。此外，鸡被认为是刚地弓形虫卵囊环境污染的敏感指标，并被用作哨兵。本研究的目的是确定常用抗体检测方法，即改良凝集试验（MAT）、间接荧光抗体试验（IFAT）和酶联免疫吸附试验（ELISA），检测刚地弓形虫感染鸡的适用性。使用实验和自然感染的鸡进行样本采集。所有鸡的感染状态均通过磁捕获（MC）实时 PCR（RT-PCR）确定。自然暴露的鸡还通过鼠生物测定法和酸性胃蛋白酶消化物（PD-RT-PCR）的常规 RT-PCR 进行检测。来自不同来源的血清和肉汁均用于检测抗刚地弓形虫抗体。在自然感染的鸡中，鼠生物测定法与 MC-RT-PCR 或鼠生物测定法与常规 PD-RT-PCR 之间存在很大的一致性。PD-RT-PCR 比 MC-RT-PCR 略敏感，因为所有（26/26）生物测定阳性的鸡在至少一种检测组织（心脏、鸡腿）中也呈阳性。通过 MC-RT-PCR，92.3%（26/26）的自然感染生物测定阳性鸡呈阳性。MC-RT-PCR 的诊断敏感性与所检查的器官明显相关。基于对实验感染鸡的 MC-RT-PCR 结果的定量评估，脑组织和心脏组织中的寄生虫浓度至少比乳房、大腿或鸡腿肌肉高 100 倍。在自然感染的鸡中，仅在 24 只心脏样本 MC-RT-PCR 阳性的鸡中，有 3 只在鸡腿肌肉中也呈阳性。在实验条件下，MC-RT-PCR 与血清学技术的一致性显示出 100%的诊断敏感性和特异性。在现场条件下，ELISA、IFAT 和 MAT 对血清的检测显示出良好的性能，可以识别出在鼠生物测定法、MC-RT-PCR 或 PD-RT-PCR 中呈阳性的鸡，其诊断敏感性分别为 87.5%、87.5%和 65.2%，诊断特异性分别为 86.2%、82.8%和 100%。从乳房、鸡腿或心脏肌肉中采集的肉汁样本的检测结果在 ELISA 中显示出相似或更好的结果。由于一些阴性鸡在 MAT 中呈假阳性，MAT 检测乳房肌肉肉汁样本的结果不如 ELISA 和 IFAT 一致。MAT 与 ELISA 和 IFAT 一样，用于检测从心脏、大腿或鸡腿肌肉采集的肉汁样本。
