Congenital toxoplasmotic chorioretinitis following reinfection

A Review of Immunological and Neuropsychobehavioral Effects of Latent Toxoplasmosis on Humans

Toxoplasmosis as a zoonotic disease has a worldwide distribution and can infect a wide range of animal hosts, as well as at least one third of the world's human population. The disease is usually mild or asymptomatic in immunocompetent individuals, but dormant tissue cysts survive especially in the brain for the host lifespan, known as latent toxoplasmosis (LT). Recent studies suggest that LT can have certain neurological, immunological psychological and behavioural effects on human including schizophrenia, bipolar disorder, Alzheimer's disease, depression, suicide anxiety and sleeping disorders. LT effects are controversial, and their exact mechanisms of action is not yet fully understood. This review aims to provide an overview of the potential effects, their basic mechanisms including alteration of neurotransmitter levels, immune activation in the central nervous system and induction of oxidative stress. Additionally, beneficial effects of LT, and an explanation of the effects within the framework of manipulation hypothesis, and finally, the challenges and limitations of the current research are discussed.

Toxoplasma gondii in South America: a differentiated pattern of spread, population structure and clinical manifestations

Toxoplasma gondii is an obligate intracellular parasite belonging to the phylum Apicomplexa. It has a worldwide distribution and can infect a wide variety of intermediate hosts, including humans. In South America, toxoplasmosis shows high health impacts, and the incidence of the disease is frequently reported and more severe than in other regions, such as Europe. Although most T. gondii infections are asymptomatic, severe manifestations can occur in cases of congenital toxoplasmosis and immunocompromised individuals. In South America, the ocular disease in immunocompetent individuals is also frequently reported. Treatment for any clinical manifestation of toxoplasmosis consists of the combination of sulfadiazine (SDZ) and pyrimethamine (PYR). However, failures in the treatment of toxoplasmosis have been reported, especially in South America, suggesting the acquisition of resistance against SDZ and PYR. Another paradigm present in the literature is that once infected with T. gondii, the host is immunologically protected from further reinfections. However, some studies indicate cases of congenital transmission of T. gondii from immunocompetent pregnant women with chronic infection, suggesting the possibility of reinfection in humans. Thus, in this review, we will cover several aspects of South American T. gondii isolates, such as genetic characterization, disease manifestation, host reinfection and drug resistance.