Fuller Torrey of the Stanley Medical Research Institute in Bethesda, Maryland his colleagues noted a link between Toxoplasma and schizophrenia – specifically, that women with high levels of the parasite were more likely to give birth to schizophrenics-to-be. Recently, however, evidence has been mounting that suggests the psychological consequences of infection are much darker than we once thought. Overall, though, the side effects of infection are thought to be minor and relatively harmless. Some of the greatest science writers of our time have waxed poetic about how it sneaks its way into our brains and affects our personalities. The idea that this tiny protozoan parasite can influence our minds is old news. For over a decade, researchers have investigated how this single-celled creature affects the way we think, finding that indeed, Toxoplasma alters our behavior and may even play a role in cultural differences beween nations.
Since Toxoplasma has no trouble affecting rats, whose brains are similar in many ways to our own, scientists wonder how much the parasite affects the big, complex brains we love so much. Around 1/3 of people on Earth carry these parasites in their heads. Of course, rats aren't the only animals that Toxoplasma ends up in. For example, Toxoplasma infection alters rat behavior with surgical precision, making them lose their fear of (and even become sexually aroused by!) the smell of cats by hijacking neurochemical pathways in the rat's brain. Incredibly, the parasite has evolved to help ensure that this occurs. Toxoplasma can only continue its life cycle and end up a happy adult in a cat's gut if it can find its way into a cat's gut, and the fastest way to a cat's gut, of course, is to be eaten by a cat. Once in this new host, the parasite changes and migrates, eventually settling as cysts in various tissues including the host's brain, where the real fun begins. These find their way into other animals that come in contact with cat crap. In the guts of cats, this single-celled protozoan lives and breeds, producing egg-like cells which pass with the cats bowel movements. Toxoplasma gondii is arguably the most interesting parasite on the planet. So, of course, we are downright offended that a simple, single-celled organism can manipulate our favorite organ, influencing the way we think and act. We scare our children with tales of monsters that eat them, and obsessively study how they work, even when these efforts are often fruitless.
We think our brains set us apart, make us special.
We're proud of them - of their size and their complexity. We human beings are very attached to our brains.
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