1. Laboratory of Evolutionary Biology, Department of Philosophy and History of Sciences, Faculty of Science, Charles University, Viničná 7, 128 00 Prague, Czech Republic

2. National Reference Laboratory for Toxoplasmosis, Šrobárova 48, 100 42 Prague, Czech Republic

One-third of humanity harbors a lifelong infection with Toxoplasma gondii, and probably about 80% are infected with human cytomegalovirus (CMV). This study aims to delineate the associations between toxoplasmosis and cognitive abilities and compare these to the associations with CMV. We evaluated the cognitive performance of 557 students, who had been examined for Toxoplasma and CMV infections, using intelligence, memory, and psychomotor tests. The results indicated cognitive impairments in seropositive individuals for both pathogens, with variations in cognitive impact related to sex and the Rh factor. Specifically, Toxoplasma infection was associated with lower IQ in men, whereas CMV was predominantly associated with worse performance by women when testing memory and reaction speeds. Analysis of the antibody concentrations indicated that certain Toxoplasma-associated cognitive detrimental effects may wane (impaired intelligence) or worsen (impaired reaction times) over time following infection. The findings imply that the cognitive impairments caused by both neurotropic pathogens are likely due to pathological changes in the brain rather than from direct manipulative action by the parasites.

A co já s tím? Tak například jsem načmárala to, samozřejmě naprosto dokonalé, schéma přenosu T. gondii na různé hostitele. Pro jistotu přikládám vysvětlivky:

Figure 1. Transmission of Toxoplasma gondii through traditional and recently described pathways. (A) Environmental contamination with oocysts affects soil, water, plant life, and, potentially, air. (B) Small animals contract toxoplasmosis from ingesting contaminated food and environmental exposure. (C) Predation leads to the transfer of the parasite as the definitive hosts consume infected prey. (D) Livestock become infected via contaminated feed and environmental sources, serving as intermediate hosts. (E) Humans risk infection by consuming undercooked meat harboring tissue cysts and unpasteurized dairy products with tachyzoites. (F) Human infection can also occur from contaminated vegetables, water, or other foods such as fish from contaminated sources, with potential direct infection from contact with feline feces. (G) Airborne transmission might be possible for humans and animals in highly contaminated environments [2]. (H) Sexual transmission in humans, specifically through penile–vaginal [3] or, potentially, oral routes [4] can be significant due to the risk of congenital toxoplasmosis. (I) Transmission through blood transfusion or organ transplantation is an acknowledged risk, albeit tempered by the stringent screening processes in place. (J) Congenital toxoplasmosis results from maternal–fetal transmission and represents a significant route of infection, with implications for neonatal health.