>>508635980 (OP)The reasons why routine testing for *Toxoplasma gondii* infection, especially in adults and regarding eye involvement, is not commonly done are multifaceted:
## 1. Nature of Infection and Symptoms
- Most healthy adults infected with *T. gondii* remain asymptomatic or have mild, nonspecific flu-like symptoms that resolve without treatment. Because the infection is often silent or mild, routine screening in the general adult population is not considered cost-effective or clinically necessary[5][2].
- Eye disease due to toxoplasmosis (ocular toxoplasmosis) is primarily diagnosed based on clinical eye examination by an ophthalmologist, supported by serology if needed. The characteristic retinal lesions and symptoms guide diagnosis more than routine screening tests[2][3].
## 2. Complexity and Interpretation of Testing
- Serologic tests detect antibodies (IgG, IgM, IgA, IgE) indicating past or recent infection, but interpretation can be complicated. IgG positivity indicates past exposure, which is very common (up to 11% in the US, higher elsewhere), and does not necessarily mean active disease[5].
- IgM antibodies can persist or reappear during chronic infection or reactivation, making it difficult to distinguish acute from chronic infection without additional specialized tests (e.g., IgG avidity, differential agglutination)[1][2].
- In immunocompromised patients, serologic tests may be unreliable, and PCR or direct detection methods are needed, but these are more complex and costly[2][4].
## 3. Risk Stratification and Targeted Testing
- Routine screening is generally reserved for high-risk groups such as pregnant women (to prevent congenital toxoplasmosis) or immunocompromised individuals (e.g., HIV patients, transplant recipients), where early detection and treatment can prevent severe outcomes[1][4].
- Universal screening is not standard in the US but is practiced in some countries like France, where it has reduced severe congenital toxoplas
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