Toxoplasma gondii (TOXO) is a neuroinvasive protozoan parasite that induces the formation of persistent microcysts in mammalian brains. It infects approximately 1.1 million people in the United States annually, and is the most successful parasite worldwide. Humans and rodents are intermediate hosts for TOXO, whereas felines are the definitive host in that sexual reproduction can only occur within the intestine of a feline. TOXO evolved unique mechanisms to evade destruction by the host, alter host behavior, and enhance its reproductive success. For the vast majority of people infected by TOXO, this chronic infection has no easily identified clinical manifestations. However, latent TOXO has been implicated in increased risk of several psychiatric disorders such as schizophrenia, bipolar disorder, general anxiety disorder, obsessive-compulsive disorder, posttraumatic stress disorder, and substance use disorders. Studies have also found associations between chronic TOXO infection and increased levels of impulsivity, aggression and self-directed violence. Nevertheless, the epidemiological literature on the association of TOXO and mental illness has substantial inconsistencies, and the underlying neurobiological mechanisms of these associations are unknown. Currently, a large body of data from animal models points to a number of potential biological pathways, and some of these mechanisms have been explored in humans. TOXO causes alterations in dopamine activity within the brain, compensatory shifts in the kynurenine pathway, and increased testosterone production. Advances in our understanding of the underlying mechanisms by which chronic TOXO infection confers increased risk of psychiatric disease could lead to discovery of novel treatment targets that could improve treatment of individuals with psychiatric disease caused by or worsened by chronic TOXO infection.
This Research Topic will present new findings on the clinical and behavioral manifestations of TOXO infection in humans and animal models, and will highlight research that sheds light on the mechanisms by which chronic TOXO may lead to these neurobehavioral manifestations.
Toxoplasma gondii (TOXO) is a neuroinvasive protozoan parasite that induces the formation of persistent microcysts in mammalian brains. It infects approximately 1.1 million people in the United States annually, and is the most successful parasite worldwide. Humans and rodents are intermediate hosts for TOXO, whereas felines are the definitive host in that sexual reproduction can only occur within the intestine of a feline. TOXO evolved unique mechanisms to evade destruction by the host, alter host behavior, and enhance its reproductive success. For the vast majority of people infected by TOXO, this chronic infection has no easily identified clinical manifestations. However, latent TOXO has been implicated in increased risk of several psychiatric disorders such as schizophrenia, bipolar disorder, general anxiety disorder, obsessive-compulsive disorder, posttraumatic stress disorder, and substance use disorders. Studies have also found associations between chronic TOXO infection and increased levels of impulsivity, aggression and self-directed violence. Nevertheless, the epidemiological literature on the association of TOXO and mental illness has substantial inconsistencies, and the underlying neurobiological mechanisms of these associations are unknown. Currently, a large body of data from animal models points to a number of potential biological pathways, and some of these mechanisms have been explored in humans. TOXO causes alterations in dopamine activity within the brain, compensatory shifts in the kynurenine pathway, and increased testosterone production. Advances in our understanding of the underlying mechanisms by which chronic TOXO infection confers increased risk of psychiatric disease could lead to discovery of novel treatment targets that could improve treatment of individuals with psychiatric disease caused by or worsened by chronic TOXO infection.
This Research Topic will present new findings on the clinical and behavioral manifestations of TOXO infection in humans and animal models, and will highlight research that sheds light on the mechanisms by which chronic TOXO may lead to these neurobehavioral manifestations.