Background and aims Despite progress made for the diagnosis of congenital Toxoplasma infection in utero and at birth, serological follow-up in first year of life remains required to exclude or confirm congenital infection. To reduce the constraints of this follow-up, we developed a test to detect anti-Toxoplasma IgG in oral fluid.

Methods In 362 patients referred for Toxoplasma serology oral fluid was collected on two micro-sponges in parallel to blood sampling. A pilot study on 212 patients aged >15 months (274 samples) was performed to validate sampling procedures and develop an in-house indirect ELISA for the detection of anti-T. gondii IgG in oral fluid. It was then applied to 150 children aged 0–15 months (341 samples) born from 133 women who seroconverted during pregnancy and 17 who remained seronegative. IgG on oral fluid were compared to serum IgG detected with MEIA AxSYM^® Toxo IgG (Abbott Laboratories).

Results The pilot study validated the acceptability and the safety of the test and the adequate duration of sampling. IgG detected in serum and in oral fluid had a parallel kinetics among newborns (correlation coefficient: 0.59, p < 0.0001), with a concordant decline in the non-infected ones (n = 110), and matching raising or stable IgG in those who were congenitally-infected (n = 23).

Conclusions Collection of oral fluid is painless and inexpensive. Our new test provides a simple and rapid method to detect anti-Toxoplasma gondii IgG and to manage newborn at risk for congenital infection. It could have many other applications in pregnant women and other groups of patients.