Taxoplasma gondii Conspiracies

An infection by T. gondii is associated with a significant 2.7 times increase in automobile accidents.

Toxoplasma gondii is an obligate intracellular, parasitic protozoan that causes the disease toxoplasmosis. Found worldwide, T. gondii is capable of
infecting virtually all warm-blooded animals, but felids such as domestic cats are the only known definitive hosts in which the parasite can undergo
sexual reproduction.

In humans, T. gondii is one of the most common parasites in developed countries; serological studies estimate that 30–50% of the global population
has been exposed to and may be chronically infected with T. gondii, although infection rates differ significantly from country to country. For example,
previous estimates have shown the highest prevalence of persons infected to be in France, at 84%. Although mild, flu-like symptoms occasionally
occur during the first few weeks following exposure, infection with T. gondii produces no readily observable symptoms in healthy human adults. This
asymptomatic state of infection is referred to as a latent infection and has recently been associated with numerous subtle adverse or pathological
behavioral alterations in humans. In infants, HIV/AIDS patients, and others with weakened immunity, infection can cause a serious and occasionally
fatal illness, toxoplasmosis.

T. gondii has been shown to alter the behavior of infected rodents in ways thought to increase the rodents' chances of being preyed upon by cats.
Support for this "manipulation hypothesis" stems from studies showing T. gondii-infected rats have a decreased aversion to cat urine.  Because cats
are the only hosts within which T. gondii can sexually reproduce to complete and begin its lifecycle, such behavioral manipulations are thought to be
evolutionary adaptations that increase the parasite's reproductive success. The rats would not shy away from areas where cats live and would also
be less able to escape should a cat try to prey on them. The primary mechanisms of T. gondii–induced behavioral changes in rodents is now known
to occur through epigenetic remodeling in neurons which govern the associated behaviors; for example, it modifies epigenetic methylation to cause
hypomethylation of arginine vasopressin-related genes in the medial amygdala to greatly decrease predator aversion. Widespread histone-lysine
acetylation in cortical astrocytes appears to be another epigenetic mechanism employed by T. gondii. Differences in aversion to cat urine are
observed between non-infected and infected humans and sex differences within these groups were apparent, as well.

A number of studies have suggested that subtle behavioral or personality changes may occur in infected humans, and infection with the parasite has
recently been associated with a number of neurological disorders, particularly schizophrenia. A 2015 study also found cognitive deficits in adults to
be associated with joint infection by both T. gondii and Helicobacter pylori in a regression model with controls for race-ethnicity and educational
attainment. However, although a causal relationship between latent toxoplasmosis with these neurological phenomena has not yet been established,
preliminary evidence suggests that T. gondii infection can induce some of the same alterations in the human brain as those observed in mice.



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