The role of blood PCR 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. The aim of this study was to investigate the potential of maternal blood PCR in differentiating between acute and chronic toxoplasmosis during pregnancy. During January to June 2023, 291 pregnant women who attended antenatal clinics in Malayer, western Iran, were tested for IgG antibodies against T. gondii using ELISA assay. The seropositive samples were subjected to anti-Toxoplasma IgG avidity and IgM ELISA test. Then the peripheral blood of women with positive sera was checked for Toxoplasma DNA by B1 gene and nested-PCR method. Out of 219 pregnant women, 77 (26.46%, 95% CI:31.53–21.39) were positive for anti-Toxoplasma IgG. The seropositivity rate was significantly higher in the age group of 39 years and older. Anti-Toxoplasma IgM was detected in two IgG seropositive samples. In total, the IgG avidity index was low in 4 women without obvious symptoms of toxoplasmosis, while it was borderline and high in 4 and 59 women, respectively. The Toxoplasma B1 gene was detected in four out of the 77 seropositive samples. According to the combination of serological and PCR results, primary infection was diagnosed in three PCR positive women with low and borderline avidity index. In this study, the primary toxoplasmosis was 1%, indicating that the risk of congenital toxoplasmosis is still a serious issue. Furthermore, it is suggested that serology results be interpreted in the context of the results of other additional confirmatory tests.