Epidemiological changes in Toxoplasma infection: a 7-year longitudinal study in pregnant women in Lyon, France, 2017-2023.

The epidemiology of Toxoplasma infection is known to vary geographically, but is also likely to vary over time, under the influence of many contributing factors. Monitoring is particularly useful in the context of preventing congenital toxoplasmosis. We took advantage of the French prenatal prevention programme to retrospectively assess changes between 2017 and 2023 in seroprevalence and incidence rates of Toxoplasma infection in pregnant women and the incidence of congenital infections. We conducted a longitudinal retrospective study including all pregnancies with known Toxoplasma status followed up at Lyon's public maternity hospitals between 2017 and 2023 (71,922 pregnancies). We used a multivariable logistic regression model to identify factors (age-group, WHO region of origin, population density of the area of residence and parity) associated with seropositivity. The seroprevalence of toxoplasmosis decreased consistently from 26.4% in 2017 to 22.1% in 2023 (p = 0.003), while maternal infection incidence remained stable at 1.3/1,000 pregnancies at risk. Notably, the seroprevalence showed a linear increase with age from 18.9% in women aged 25-29 years to 38.0% in women aged ≥40 years (p < 0.001). The seroprevalence was lower in pregnant women living in rural areas [adjusted seroprevalence ratio (aPR) = 0.87, 95% CI: 0.82-0.92] and higher in multiparous women (aPR = 1.08, 95% CI: 1.04-1.12). This study confirms the ongoing decline in toxoplasmosis seroprevalence while seroconversions remained stable, indicating a need for more tests in seronegative women in the future. These findings highlight the need for ongoing monitoring and refinement of congenital toxoplasmosis prevention strategies in high-income countries.