Twenty-six percent of new Trypanosoma cruzi infections occur through mother-to-child transmission, and as vector and blood donation control improve, the proportion attributable to congenital infection will grow. An estimated 8 million persons have lifelong T. cruzi infection in Latin America. Approximately 5% of T. cruzi infected women give birth to infected infants at risk of clinically manifest Chagas disease at birth, shortly after birth or later in life. Laboratory-based screening is essential to detect congenital infection, and early detection is important to the most effective treatment. In high-prevalence areas, one promising approach may be universal newborn screening, as is routine for some genetic and metabolic disorders. However, there is no sufficiently sensitive, specific and logistically feasible test to diagnose congenital T. cruzi infection early in life, and current Latin American programs have low completion rates. The current standard for congenital T. cruzi diagnosis throughout Latin America relies on microscopy of concentrated cord blood, followed by serology at 9 months. In our previous study in Bolivia, we found a transmission rate of 6.5% (10/154 infants of infected mothers). However, none of the infected infants were detected by microscopy in cord blood, and only 40% were detected by microscopy in any of the 3 additional specimens collected in the first 30 days (a much more intensive sampling schedule than routine programs can sustain). Because hospitals lack beds, women are often discharged within 12-18 hours of delivery, complicating follow-up efforts. Prenatal screening with current rapid tests had only 90% sensitivity, and mothers with false-negative results seldom brought infants back for follow- up. We found that PCR-positive women were significantly more likely to transmit T. cruzi than seropositive women with negative PCR, and mothers of infected infants had significantly higher parasite loads. PCR detected 89% of infected infants at birth and100% by 30 days. Despite intensive efforts, only 58% of at-risk infants completed 9-month follow-up. We estimate that current screening programs miss more than half of all infected infants.
The aim of this application is to develop and evaluate novel techniques (Loop Mediated Isothermal Amplification, antigen detections assays and enhanced IgM assay for antibodies to Shed Acute Phase Antigens), with the ultimate aim of developing a rapid, point-of-care format to test neonates. In addition we will assess the use of prenatal PCR and T. cruzi-specific immune responses to identify the women with the highest risk of transmission, in order to ensure more intensive follow-up of their infants.
Chagas disease causes more deaths in the Americas than any other parasitic disease, and women infected with the parasite can pass it to their infants during pregnancy. Current methods of diagnosis are poor, and infants are often left undiagnosed and can become very ill. In this application, we propose to test different methods of diagnosing Chagas disease in mothers and their infants, in order to begin early and appropriate treatment.
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