Mind-Control Microbe

Can a cat parasite infect humans as well? An article on Discover suggests that Toxoplasma gondii is altering the behaviour of its human hosts, and can even cause a shift in the sex ratio of their babies in favour of males.

Five years ago, Oxford University zoologists showed that the parasite Toxoplasma gondii alters the brain chemistry of rats so that they are more likely to seek out cats. Infection thus makes a rat more likely to be killed and the parasite more likely to end up in a cat—the only host in which it can complete the reproductive step of its life cycle. The parasite also lives in the brain cells of thousands of species, including about 60 million supposedly symptom-free Americans. Studies over the past few years have suggested that toxoplasmosis infections in humans, too, may cause behavioral changes—from subtle shifts to outright schizophrenia. Two studies this year add even weirder twists.

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