Is the incidence of congenital toxoplasmosis declining?

Prenatal infection with the protozoan parasite Toxoplasma gondii can cause congenital toxoplasmosis (CT), an often fatal or lifelong-disabling condition. Several studies of human populations have reported temporal decreases in seroprevalence, suggesting declining CT incidence. However, the consistency of this trend among diverse populations remains unclear, as does its implication for prenatal screening programmes, the major intervention against CT. Using temporally resolved data on the seroprevalence of T. gondii in various countries, we discuss how the parasite's changing epidemiology may affect trends in CT incidence in varying and counterintuitive ways. We argue that parasite stage-specific serology could be helpful for understanding underlying causes of secular changes in seroprevalence. Furthermore, we highlight the importance of updating cost-effectiveness estimates of screening programmes, accounting for neuropsychiatric sequelae. An emerging body of evidence indicates that exposure to Toxoplasma gondii is decreasing among numerous human populations, though most data are from high-income countries. Considering this changing epidemiology, the cost-effectiveness of prenatal screening programmes should be re-examined while accounting for other (not currently considered) sequelae of congenital toxoplasmosis (CT), including possible neuropsychiatric effects. Parasite stage-specific serology should be further developed and applied to serum samples from animals and humans to understand the possible causative mechanisms underlying seroprevalence decreases. The effect of seroprevalence declines on the incidence of CT will be context specific, varying according to parasite genotype, population demographics, and the local epidemiology. [ABSTRACT FROM AUTHOR]