evidence: The parasite does not usually cause much damage to immunocompetent hosts; however, it has been associated with cognitive impairments, emotional disturbances, and schizophrenia (8). Recent studies have shown that the transmission of T. gondii is also facilitated by the ability to modify its host’s behavior (9-11). According to the manipulation hypothesis, specific parasites can change host behavior for their own benefit (1). Toxoplasma gondii-infected rats and mice had a less innate fear of the odor of cat urine; this effect is useful for the parasite (1). The mechanisms for these changes have not been clearly identified to date; however, there is evidence that toxoplasmosis increases dopamine levels in the amygdala in the brain of infected mice by genes encoding the tyrosine hydroxylase enzyme production (12). It is noticeable that the hippocampus and amygdala are structures in the brain associated with natural defense behaviors and emotion processing (13). [...] Zareian P, Mirzaii Dizgah I, Saddel M, Khodabandehloo F. Effects of Toxoplasma gondii infection on anxiety, depression and ghrelin level in male rats. J Parasit Dis. 2016;40(3):688-93. [PubMed ID: 27605768]. [PubMed Central ID: PMC4996174]. https://doi.org/10.1007/s12639-014-0561-0.