PCR-based diagnosis is not always useful in the acute acquired toxoplasmosis in immunocompetent individuals

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.

Automated summary

Toxoplasmosis is a widespread zoonotic disease that can cause a range of illnesses. While laboratory diagnosis often relies on detecting antibodies, PCR is suggested as a more reliable diagnostic tool. A study on individuals with acute acquired toxoplasmosis found that PCR did not detect any parasitic DNA, indicating the need for further research on parasitemia kinetics and the importance of serological criteria in diagnosis.