Chapter 20 Pathophysiological mechanisms of Toxoplasma gondii infection in the central nervous system (CNS)

Toxoplasma gondii is an intracellular parasite of the phylum Apicomplexa that infects a wide range of warm-blooded animals, including humans. Its global seroprevalence varies significantly, reaching up to 80% in some regions. While infection in immunocompetent individuals often results in mild or asymptomatic illness, T. gondii is a leading cause of food-borne illness–related deaths and a common opportunistic pathogen among immunocompromised individuals. The parasite's complex life cycle involves felines as definitive hosts and both sexual and asexual stages, with tissue cysts playing a crucial role in its persistence and transmission. In the central nervous system, T. gondii forms latent tissue cysts that manipulate host neurotransmission and behavior by disrupting the synthesis of neurotransmitters, including dopamine and norepinephrine (NE). The parasite downregulates dopamine beta-hydroxylase, leading to decreased NE levels and altered noradrenergic signaling, potentially contributing to neuropsychiatric disorders and cognitive impairments.