Lyon Clinical Research Program on Maternal and Congenital Toxoplasmosis Based on the Toxo-Ly Cohort: Risks and Clinical Consequences, Prevention, Diagnosis and Treatment

Several decades ago, France has made the choice to implement a national prevention program for congenital toxoplasmosis. The identification in their first trimester of pregnancy of all pregnant women who are susceptible to Toxoplasma infection has been mandatory since 1985. In 1992, the decision was made to extent the program to the monthly retesting of all women identified as not immune, in an attempt to reduce the number of severely infected children.

The systematic detection of all maternal and congenital infections has generated many questions from clinicians, biologists, parents and older patients, on the short and long-term prognosis of congenital toxoplasmosis, on the best tests to use to diagnose infections in mothers and children, on the efficacy of existing treatments, and on how to manage patients in the long-term.

The need to answer these many questions has prompted the medical team working within the laboratory and the outpatient department of the Parasitology Department at the Croix-Rousse Hospital in Lyon to implement a clinical research program. It is based on the systematic inclusion in our cohort of all pregnant women whose infection is confirmed, on their follow up, in order to monitor the outcome of pregnancy 2) and on the follow up of their children in order to confirm their infection or to rule it out. All congenitally infected subjects undergo clinical examinations, serological tests and ocular examination at least once a year without age limit.

The following data are prospectively collected in a dedicated database: gestational age at maternal infection and corresponding serological profile; type and dates of maternal treatment; findings of ultrasound tests and amniotic fluid analysis; serological and clinical findings at birth; types and dates of postnatal treatment; postnatal serological profiles; infection status at one year of age; long term clinical (ophthalmologic) et serological findings.

These data have allowed producing original findings on the risk of maternal-foetal transmission according to gestational age at maternal infection, on the long term ophthalmological outcome of congenital toxoplasmosis and to offer guidelines for the diagnosis, treatment and follow-up of maternal and congenital infections.

These efforts are still to be maintained in the future in order

• to further analyse the impact of puberty, pregnancy, or adult co-morbidities on the risk of ophthalmological events
• to increase precision around our risk estimates for materno-foetal transmission,
• to continue innovating in terms of diagnostic strategy to improve tests performances and reduce costs
• to explore new potential clinical outcomes such as neuropsychiatric disorders associated with congenital and postnatal infection
• to determine if infections due to oocysts could have different clinical outcomes than those due to the ingestion of cysts
• to assess the efficacy of treatments for maternal and congenital infections