The terror of Toxoplasma gondii, the brain-controlling parasite that lives in cats, has by now been hyped enough to make everyone give their cats a sidelong glance. The parasite works something like this: It reproduces and grows in cats, but can be spread to any number of organisms. In rodents, toxoplasma makes mice fearless towards cats; in essence, the parasite seems to make rodents make themselves easier for a cat to eat, which is then of course infected by the parasite.It's a brilliant example of the ruthless efficiency that makes many parasites work, and–considering people are regularly infected too–might explain why cats are so popular on the internet. Yes, I'm saying that /r/awww is populated by toxoplasma zombies who can't stop obsessing over their cats.It all sounds like a rather fantastic tale, even if the parasite's effects have been well-observed. But with a quarter of the global population infected, you have to ask: Why don't our immune systems fight back against toxoplasma? Thanks to some research published today in PLoS Pathogens, we've now got a better idea of how toxoplasma actually works.The paper, published by a team led by Jonas Fuks of the Karolinska University Hospital Huddinge in Stockholm, suggests that toxoplasma can hijack our dendritic cells, which act as the "gatekeepers" of our immune system. According to the authors, toxoplasma—a single-celled, motile organism which would otherwise move around semi-randomly—seems to ride on the back of dendritic cells to take a quick ride straight to the brain. If that sounds familiar, it's because toxoplasma apparently works much like a Trojan horse.The team showed that, after gaining access to dendritic cells, the parasite causes them to release a neurotransmitter called GABA, which counts among its effects the inhibition of fear and anxiety. (In fact, some anti-anxiety medications work by preventing the reuptake of GABA.) In essence, toxoplasma flips the neurochemical switch that helps you deal with fear.Read the rest over at Motherboard.
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