The role of blood nested B1-gene in differentiation of acute toxoplasmosis from chronic infection during pregnancy.

Abstract

Toxoplasma gondii causes common parasitic infection, and congenital toxoplasmosis is considered a serious public health concern. This study aimed to evaluate the utility of maternal blood PCR in distinguishing acute from chronic toxoplasmosis during pregnancy. From January to June 2023, 291 pregnant women in Malayer, western Iran, were screened for T. gondii IgG antibodies via ELISA. Seropositive samples underwent further testing for IgG avidity and IgM antibodies. Peripheral blood samples from IgG-positive women were then analyzed for T. gondii DNA by targeting the B1 gene through nested PCR. Among the 291 pregnant women, 77 (26.46%; 95% CI: 21.39-31.53) tested positive for anti-Toxoplasma IgG. Seropositivity rates were significantly higher in women aged 39 years or older. Anti-Toxoplasma IgM was detected in two of the IgG-positive samples. IgG avidity results showed low levels in four asymptomatic women, borderline levels in four women, and high levels in 69 women. The Toxoplasma B1 gene was detected in four out of the 77 seropositive samples. Based on the combination of serological and PCR results, primary infection was diagnosed in three PCR-positive women with low and borderline IgG avidity. Finally, acute toxoplasmosis was diagnosed in three pregnant women (1%), indicating that the risk of congenital toxoplasmosis remains a serious issue. Furthermore, these findings suggest that serology results should be interpreted in conjunction with additional confirmatory tests.