Toxoplasma gondii infection in the context of the risk of schizophrenia development

Abstract

There are three infectious stages in the life cycle of T. gondii: tachyzoites, which facilitate the spread of the infection during acute infections, bradyzoites, which maintain chronic infection, and sporozoites, which are spread through the host's environment in the form of oocysts. Although infection induces a strong innate and acquired immune response controlling multiplication of the parasite, the infection is not eliminated. The host retains a lifelong latent infection characterized by the presence of cysts in the tissues. Tissue cysts become established in various cells, particularly in long-lived differentiated cells, such as neurons and muscle cells, thereby ensuring long-term infection. In humans, T. gondii has tropism for the brain, which may influence the occurrence of certain mental disorders, including schizophrenia, personality disorders, dementia, and suicidal tendencies (25).Latent infection with T. gondii involves the presence of the parasite without clinical symptoms in immunocompetent patients. However, recent studies have shown a continual inflammatory state in the central nervous system following chronic T. gondii infection in rodents. Subtle neuromodulatory properties of the parasite in humans and mice have been the subject of recent research. Significant changes in the brain following T. gondii infection in animal models include activation of the glia and recruitment of peripheral immune cells to the central nervous system (14).For this reason, studies have focused on how T. gondii is linked to psychiatric diseases and neurocognitive processes. Research has shown a correlation between T. gondii infection and schizophrenia. Interestingly, hallucinations, which are a key characteristic of schizophrenia, have occurred in some acute cases of T. gondii infection. Moreover, data from as early as 1950 showed that most hospitalized psychiatric patients tested positive for the presence of T. gondii. The culmination of these findings was a recent metaanalysis of 38 studies suggesting that T. gondii infection increases the risk of schizophrenia 2.7 times (19). Dudzińska E., Listos P., Gryzińska M., Krukowski H., Trawińska B.Toxoplasma gondii infection in the context of the risk of schizophrenia development Summary Toxoplasma gondii (T. gondii) is a protozoan parasitizing all warm-blooded mammals, including humans. The main source of infection is contact with the feces of infected animals, particularly housecats -the definitive hosts, in which T. gondii completes its life cycle. Alternative sources of infection are contact with and consumption of contaminated meat (particularly pork), transmission from mother to fetus, and infection by oocytes present in the soil or in polluted water. T. gondii is geographically ubiquitous; its level of seroprevalence is estimated to range from about 3% in South Korea to 76% in Costa Rica.Despite great efforts and considerable progress, toxoplasmosis remains a serious health threat worldwide. There is currently no available vaccine, and anti-toxoplasmosis drugs have s...