Seroprevalence and Molecular Investigation of Toxoplasmosis Among Working Children in Tehran

background: Toxoplasma gondii is a pathogenic protozoan that causes toxoplasmosis and spreads worldwide. Objectives: This study aimed to investigate the prevalence of toxoplasmosis by serological and molecular methods in working children and a control group in Tehran. Methods: The study participants comprised 460 children aged 7 - 14 years, including 278 working children and 182 age-matched controls. Blood samples were collected, and a serological test was performed to evaluate IgM and IgG antibodies against T. gondii. Peripheral blood mononuclear cells (PBMCs) were isolated from the blood specimens by gradient centrifugation method. Real-time polymerase chain reaction (PCR) was performed using primer B1 on PBMC samples in children’s blood to determine the status of Toxoplasma infection. Results: Seroprevalence of IgG and IgM antibodies against T. gondii was 24.8% and 0.7%, respectively, in working children; however, in the control group, 12.1% and 2.2% had IgG and IgM antibodies against T. gondii, respectively. The mean IgG titer was 160 ± 86.39 IU/mL and 69.36 ± 88 IU/mL for working children and the control group, respectively (P 0.0001); however, the mean IgM titer was 4.65 ± 3.04 IU/mL and 3.85 ± 4 IU/mL for working children and control group, respectively (P = 0.8187). Real-time PCR results indicated two (0.7%) positive cases among working children and three (1.65%) samples in the control group. The present study showed a significant di erence between working children and the control group regarding the frequency of IgG antibodies (P = 0.0012). However, there was no significant di erence in the frequency of IgM antibodies in the two mentioned groups. Conclusions: Seroprevalence of IgG antibody against T. gondii was more in working children than in the control group in Tehran. This investigation revealed a significant di erence in frequency and titer of IgG antibodies between working children and the con-trol group. More exposure to the soil and contaminated hands before drinking water or food may be considered factors in the development of toxoplasmosis infection in these children.