Causative Agents

Toxoplasma gondii, an obligate intracellular protozoa parasite, is the causative agent of the disease. The genome of the parasite, which can be found in different forms (oocyst, tachyzoite, bradyzoite) at different stages, is approximately 80 Mb in size and has 11 chromosomes, except for the sexual reproduction period in cats.


T. gondii can cause infection in all mammals including humans and birds. This infection is widespread throughout the world and is reported to affect approximately one third of the world’s population. Age, lifestyle (cat feeding, raw meat consumption, etc.) and geographical factors affect the distribution of infection worldwide (France 80%, Turkey 39-75%, Austria 62%, UK 50%, USA 30-40%). The frequency of congenital infection is 1-3 per 1000 live births and can be very serious in immunocompromised patients (50%).

Modes of Transmission

Transmission of the infection usually occurs through infected cat feces, contaminated food and water, cooked or undercooked meat infected with cysts (bradyzoites), raw eggs and dairy products, blood and organ transplants, placenta from mother to baby and rarely through inhalation.


Toxoplasmosis is difficult to diagnose as it can be confused with infectious and non-infectious infections. It can be detected by indirect serological methods based on antibody detection (Sabin-Feldman Dye Test, Lysis Test, Agglutination, Precipitation, Fluorescent Techniques, ELISA (IgG, IgM, IgA, IgE) etc.) or direct methods (PCR, Hybridization, isolation of the parasite, histology etc.).

Commonly used serologic tests can cause false positive results because they can detect antibody levels (IgM) that remain detectable in the body for a long time (1-2 years). In addition, in the process of specific antibodies reaching a detectable level after infection (1-3 weeks) (especially determination of the active period in congenital toxoplasmosis) and in people with immunodeficiency, evaluation in serological diagnostic methods becomes difficult. Tissue culture and isolation methods used as an alternative to these methods are time consuming and not easy and pose a risk to health.

With the Real-Time PCR method, which is based on the detection of T. gondii DNA from body fluids and tissues, all these handicaps are avoided, a fast and reliable solution is offered, and parasite quantification can be realized, which enables the follow-up of treatment.

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