Is Toxoplasma gondii a Trigger of Bipolar Disorder?

Abstract

Toxoplasma gondii, a ubiquitous intracellular parasite, has a strong tropism for the brain tissue, where it forms intracellular cysts within the neurons and glial cells, establishing a chronic infection. Although latent toxoplasmosis is generally assumed to be asymptomatic in immunocompetent individuals, it is now clear that it can induce behavioral manipulations in mice and infected humans. Moreover, a strong relation has emerged in recent years between toxoplasmosis and psychiatric disorders. The link between T. gondii and schizophrenia has been the most widely documented; however, a significant association with bipolar disorder (BD) and suicidal/aggressive behaviors has also been detected. T. gondii may play a role in the etiopathogenesis of psychiatric disorders affecting neurotransmitters, especially dopamine, that are implicated in the emergence of psychosis and behavioral Toxoplasma-induced abnormalities, and inducing brain inflammation by the direct stimulation of inflammatory cytokines in the central nervous system. Besides this, there is increasing evidence for a prominent role of immune dysregulation in psychosis and BD. The aim of this review is to describe recent evidence suggesting a link between Toxoplasma gondii and BD, focusing on the interaction between immune responses and this infectious agent in the etiopathogenesis of psychiatric symptoms.

Spatial and simultaneous representative seroprevalence of anti-Toxoplasma gondii antibodies in owners and their domiciled dogs in a major city of southern Brazil

“…Mental illnesses and behavior alterations, accompanied by cognitive deficits, have been reported as a latent form of toxoplasmosis, which may lead in human patients to workplace accidents [65]. Likewise, as behavior problems have been reported in both human beings and rats [66–68], dogs may also present with such alterations. However, since aggressiveness has not been previously reported in infected dogs, exclusion of aggressive dogs may not have biased the present study.…”

Toxoplasmosis and Public Health Genomics

“…T. gondii, a neurotrophic parasite, plays a role in the development of schizophrenia and causes behavioral changes, suicide attempts, and neuropathological degenerations in the brain tissue [53][54][55][56]74]. T. gondii has a role in the development of behavioral disorders via changes in neuroimmunomodulation and neurotransmission, yet pathophysiological mechanisms are not fully understood by scientists [57,58].…”

“…gondii and schizophrenia relations have been linked in many studies [63], and generally it's accepted that T. gondii triggers psychiatric disorders via affecting neurotransmitter secretion [54]. It is known that the T. gondii genome contains two aromatic amino acid hydroxylases that can directly affect dopamine and/or serotonin biosynthesis [64].…”

Acute Toxoplasma gondii infection alters the number of neurons and the proportion of enteric glial cells in the duodenum in Wistar rats

“…Toxoplasma gondii infection afflicts up to one‐third of the world's population . However, most infected patients are immunocompetent, and the infection is considered inert, with the exception of psychiatric changes that are associated with seropositivity and the presence of cysts in the brain . The infection occurs mainly after ingesting the parasite .…”

“…1 However, most infected patients are immunocompetent, and the infection is considered inert, with the exception of psychiatric changes that are associated with seropositivity and the presence of cysts in the brain. [2][3][4][5] The infection occurs mainly after ingesting the parasite. 6 The parasite then rapidly proliferates in the host's intestine by passing through the intestinal barrier and spreads, thus characterizing the acute phase of infection.…”