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Background: Children with β-thalassemia major who regularly receive blood transfusion are at risk of developing transfusion-transmitted infection. Toxoplasmosis is a common and a serious parasitic disease with high prevalence and could be transmitted through blood transfusion from healthy asymptomatic donors. However, screening Toxoplasma gondii before blood donation has not been considered. The objective of this study was to determine the prevalence of T. gondii antibodies among thalassemia children undergoing blood transfusion., Methods: In a case-control study, serum samples from 211 thalassemia children and 100 control children were investigated for Toxoplasma IgM and IgG using the enzyme-linked immunosorbent assay. Positive serum samples for IgG antibodies to T. gondii were further subjected to IgG avidity enzyme-linked immunosorbent assay., Results: The seroprevalence of Toxoplasma infection among thalassemia children was 23.2% and 53.6% for IgM and IgG anti-Toxoplasma antibodies, respectively. Whereas in the control group, the prevalence was 5% and 18% for IgM and IgG anti-Toxoplasma antibodies, respectively. There is a significant statistical difference between thalassemia and control groups regarding the prevalence of toxoplasmosis. From these positive IgG samples, 65.5% have low avidity indicating recent infection while 38.73% have high avidity indicating past infection., Conclusion: Due to the high serologic infection rate of toxoplasmosis among thalassemia pediatric population in this study with no existing effective therapies and no available T. gondii vaccine, appropriate strategies are critical for reducing the risk of that infection. Screening of blood for T. gondii antibodies should be considered before transmission to those children especially in countries with a high prevalence of toxoplasmosis.

Toxoplasma gondii congenital transmission depends partially on parasite load and genotype. Both factors were examined in 4 mother/newborn pairs with perinatal infection acquired in central Mexico. Type I and type I-related strains were identified. These results add information regarding T. gondii strains prevailing in humans, although neither the genotype nor the load were related to vertical transmission or damage.

We report a case of asymptomatic congenital toxoplasmosis following a periconceptional infection of the mother. Fetal infection is very uncommon in such a situation, and mostly associated with fetal damage. We recommend that newborns undergo postnatal screening, even after maternal periconceptional infection, and receive specific therapy to reduce long-term sequelae.

We report the vertical transmission of congenital toxoplasmosis from a chronically infected immunocompetent woman to her child. On the background of published knowledge in this field, vertical transmission must have developed after maternal reinfection or reactivation of the preexisting disease.

Congenital toxoplasmosis results from maternal primary infection during pregnancy. In our serologic screening study 42 of 16,733 pregnant women had findings suggestive of primary infection. Here we document the outcome of their offspring, 37 of 39 liveborn children. After 12 months postnatally, serologically verified congenital toxoplasmosis appeared in 4 children. All these children had persisting IgG at the age of 12 months by both the dye test and the IgG enzyme-linked immunosorbent assay. All the congenitally infected infants had also specific IgM and IgA and showed significant increases in avidity of specific IgG during the 12-month follow-up. One of them had a unilateral retinal scar and intracranial calcifications. An additional 3 infants of the mothers with primary infection during early pregnancy presented with unilateral retinal scars but without seroresponses during the first 12 months of life. Maternal high avidity of IgG during the first trimester is a strong indicator against primary infection during pregnancy; the fetuses of such mothers are at low risk for congenital toxoplasmosis.