That's a lot of cat poop, and the parasites embedded within bear a long shelf-life. Oocysts can survive in warm climates with moist soil or seawater for one year. Even one oocyst is enough to infect a human.
So can this parasite actually control human brains?
Not everyone infected with Toxoplasma gondii suffers toxoplasmosis, a serious illness that can cause miscarriage, fetal development disorders, retinal damage, brain damage, and death. The majority of the 2 billion people infected by the parasite don't know they have it, and never will.
But for those who do develop toxoplasmosis, the results can be devastating. "It's the most common cause of infection of the back of the eye," says Dr. Rima McLeod, professor of ophthalmology & visual science and pediatrics, and medical director of the Toxoplasmosis Center at the University of Chicago. "It can cause epilepsy, it can be devastating for a baby, and it can be devastating for someone with a compromised immune system." Those most at risk are pregnant women, who can transmit the infection to fetuses in utero, children, individuals undergoing immunosuppressive therapy like cancer treatment, and individuals suffering immunosuppressive diseases like AIDS.