In the United States, almost one in four residents over the age of 12 has the infection. In other parts of the world, rates are as high as 95 percent. An unlucky minority of these infected people become quite ill. Most, however, don’t even know that their muscles and brains carry the parasite.
“Where science meets science fiction” is how Michael Dickinson of the University of Washington in Seattle describes studies of parasites that hack into their hosts’ nervous systems. The Journal of Experimental Biology, where Dickinson serves as an editor, dedicated its Jan. 1 issue to this emerging field, dubbed “neuroparasitology.” In those pages and elsewhere, clues to T. gondii’s bizarre biology are emerging. And growing evidence suggests that the hidden parasite may have visible effects.
Studies comparing the infected and the noninfected raise the possibility that the parasite tweaks a person’s personality or ups the risk of suicide attempts, brain cancer and schizophrenia. Studies in people even report links between T. gondii and traffic accidents, greater odds of having sons than daughters, extra height and unusual opinions about the smell of urine.
If so much of what people do turns out to have a touch of parasite about it, then the notion of normal human behavior may have to change. What is “routine” for people might need to encompass not just the activities of a Homo sapiens by itself, but also the doings of Homo sapiens as a walking ecosystem where microbes and mammal intermingle.
Whatever the mechanism, the link between parasite infection and schizophrenia looks moderately strong based on 38 studies, Yolken and his colleagues concluded last May in Schizophrenia Bulletin.
Originally posted by Grimpachi
reply to post by jessejamesxx
BTW I don’t think cats are evil. I like mine.
Originally posted by stirling
My cat pickd me out and simply moved in.....hmmmmmmmm.......
I have been feeding it and caring for it since as well.......hmmmmmmmmmm
Ya dont think?
Naaw thats too far out.........
In a paper published in the online edition of Proceedings of the Royal Society, United States Geological Survey researcher Kevin Lafferty argues that a significant factor in why some countries exhibit higher levels of neuroticism than others may be the prevalence of the parasite Toxoplasma gondii. The study also indicates that it may influence a society’s preference for strict laws, an expression of uncertainty avoidance, and its valuation of ‘masculine’ priorities such as competitiveness and financial success over ‘feminine’ values like relationship-building.
“Toxoplasma appears to explain 30% of the variation in neuroticism among countries, 15% of the uncertainty avoidance among Western nations and 30% of the sex role differences among Western nations,” Lafferty said via e-mail.
Lafferty analyzed preexisting data on Toxoplasma prevalence and mean trait levels in 39 countries. He found a significant linear correlation between latent Toxoplasma prevalence and neuroticism with a few outliers, including the unusually neurotic nations of Hungary and China and the notably easygoing Turkey.
Links between Toxoplasma, uncertainty avoidance and concerns about masculinity initially appeared to be insignificant but later emerged when Lafferty focused on Western nations.
Lafferty based his analysis on earlier research by Jaroslav Flegr, a parasitologist at Prague’s Charles University, which showed that in humans, Toxoplasma infection correlates highly with certain personality traits: Infected men tended to have lower levels of intelligence, superego strength and novelty-seeking, while infected women exhibited higher levels of intelligence, superego strength and warmth. Infected people of both sexes tend to be susceptible to feelings of guilt.
“We have the data showing that Toxoplasma-infected men are scored as more dominant and more masculine than Toxoplasma-free men by female observers.”
Robert Sapolsky, a neuroscientist at Stanford University, and his colleagues have carried the experimental torch foreward. In 2006, they demonstrated just how precise Toxoplasma’s effects are. They found that infected rats did not lose their fear across the board. Dog urine still spooked them, and they could be trained to get scared of new stimuli. Only their innate fear of cats changed. Sapolsky’s team then looked at where the parasite actually ended up in the rat brain. They found Toxoplasma cysts clumped around the amygdala, a region of the brain that’s heavily involved in fear and other emotions.
Now Sapolsky and his colleagues have looked even closer at the parasite’s effects. They had rats sniff various odors and then examined their brains to look for a telltale protein called c-Fos. When neurons fire, they produce c-Fos, and so the more active a region of the brain, the more c-Fos accumulates in it. The scientists found two big differences in infected rat brains when they sniffed cat urine, both of which occurred in the region around the amygadala. A circuit in the brain that helps produce defensive behaviors became less active.
Near that circuit is another circuit that triggers sexual arousal.
And the parasite also altered this sexual arousal circuit. It increased the activity of those neurons.