Mechanisms of Behavioral Change in Hosts of Toxoplasma gondii: A Review

The parasite Toxoplasma gondii is a highly ubiquitous parasite that latently infects an estimated 33% percent of the global population. Toxoplasmosis is of obvious clinical significance due to the extremely high risks to the unborn who contract it congenitally. Less attention has been given to a more subtle aspect of latent infection, which is the behavioral alterations that are commonly experienced by those who contract the parasite. Infected individuals commonly display a variety of altered behaviors, such as increased aggression and risk-seeking behaviors, depression, higher tendency towards suicide and self-directed violence, a loss of fear response, and a greatly increased predisposition for schizophrenia. Many mechanisms have been proposed to explain these phenomena, and some will be described here, with an emphasis on neurotransmitter and endocrine dysregulation. It is likely that the best framework for understanding behavioral alteration in hosts of Toxoplasma is one that incorporates the interactions between several proposed mechanisms.