Toxoplasma gondii Infection as a Risk Factor for Major Psychiatric Disorders: Pre-clinical and Clinical Evidence

The link between toxoplasmosis and major psychiatric disorders, such as schizophrenia and bipolar disorder, has been an important field of investigation in immunopsychiatry. Toxoplasma gondii is a parasitic protozoan that lodges in parenchymatous tissues like the central nervous system, disrupting their normal functioning and activating immune cells. T. gondii infection may occur in two different ways: (i) acquired through consumption of T. gondii as a foodborne pathogen and (ii) vertically from mother to fetus. Maternal toxoplasmosis infection activates the immune system of both mother and fetus. Fetal brain can be affected by such immune activation, explaining in part the association between congenital toxoplasmosis and schizophrenia. Moreover, T. gondii may induce a disruption in dopaminergic signaling pathways in the brain, which may lead to psychotic episodes. In this chapter, we discuss the pre-clinical and clinical evidence on the association between perinatal and postnatal T. gondii infection and the development of neuropsychiatric disorders, as well as the pathophysiological mechanisms.