Laboratório de Parasitologia, Instituto Nacional de Infectologia Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil.
Laboratório de Pesquisa Clínica em Neuroinfecções, Instituto Nacional de Infectologia Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil.
Parasitol Res. 2021 Feb;120(2):763-767. doi: 10.1007/s00436-020-07022-6. Epub 2021 Jan 8.
Toxoplasmosis is the most prevalent zoonosis in the world and is associated with a large spectrum of diseases. Acute acquired toxoplasmosis (AAT) is considered a benign and self-limiting disease but severe postnatal infections have been reported, particularly in South America. Laboratory diagnosis is based on the detection of anti-Toxoplasma gondii IgM, IgG, and presence of low IgG avidity. However, these assays present limitations, and therefore, PCR has been suggested as an alternative diagnostic tool. In this study, we performed real-time and nested PCR in DNA blood samples from 59 individuals with AAT lasting less than 80 days. None of the patients had parasitic DNA detected by PCR, even in the more severe cases or when blood was collected early after disease onset. These negative results indicate that the parasitemia kinetics needs investigation to determine the best time for blood sampling, especially in immunocompetent individuals. Thus, we emphasize that a negative PCR result does not exclude recent T. gondii infection, and serological criteria are still decisive for the laboratory diagnosis of AAT.
弓形体病是世界上最普遍的人畜共患病，与多种疾病相关。急性获得性弓形体病（AAT）被认为是一种良性和自限性疾病，但在南美洲，已有严重的产后感染报告。实验室诊断基于检测抗弓形体 IgM、IgG，以及低 IgG 亲和力的存在。然而，这些检测方法存在局限性，因此建议 PCR 作为替代诊断工具。在这项研究中，我们对 59 例持续时间不到 80 天的 AAT 患者的血液 DNA 样本进行了实时和巢式 PCR。PCR 未检测到任何患者的寄生虫 DNA，即使是在更严重的病例或疾病发作后早期采集血液时。这些阴性结果表明，需要研究寄生虫血症的动力学，以确定最佳的采血时间，尤其是在免疫功能正常的个体中。因此，我们强调，PCR 结果阴性并不能排除近期弓形体感染，血清学标准仍然是 AAT 实验室诊断的决定性因素。
