MONDAY, Dec. 10 (HealthDay News) -- New research reveals how toxoplasma -- a parasite commonly found in cat litter boxes -- might affect behavior and mental health in humans.
Between 30 and 50 percent of the world's population is believed to be infected with the Toxoplasma gondii parasite, but very few people have symptoms because the immune system usually keeps the parasite from causing illness. T. gondii is also found in animals, particularly domestic cats.
People usually contract T. gondii in two ways -- by eating the undercooked flesh of infected animals or through contact with cat feces.
The parasite causes a disease called toxoplasmosis. Most people experience mild flu-like symptoms before it goes into a chronic and dormant phase. But the disease can be fatal in people with weakened immune systems and in fetuses, which can be infected through the mother. This is why women are advised to avoid contact with cat litter boxes while pregnant.
Some studies have shown that mental health disorders such as schizophrenia, depression and anxiety are more common in people with toxoplasmosis, while others have suggested that the disease can influence a person's levels of aggression, extroversion and risk-taking, the researchers from the Karolinska Institute in Sweden pointed out.
In this new study, a laboratory experiment conducted by the researchers found that human dendritic cells -- which are an important part of the immune system -- started secreting the signaling chemical GABA after being infected with toxoplasma.
In another experiment, this time using mice, the scientists introduced the parasite to the brain, and then traced the movement of infected dendritic cells from the brain through the body where it spread and continued to affect the GABA system, according to the study published Dec. 6 in the journal PLoS Pathogens.
Among its roles, GABA inhibits feelings of fear
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