This is your brain on cats?

Torrey's prime suspect was Toxoplasma gondii , an organism doctors are typically taught about in their first year of medical school. T. gondii , as it is informally known, is carried and transmitted to humans and other animals solely by cats. In many animals, the organism produces seizures, tremors, and head shaking, similar to what Torrey's pet cat went through decades earlier. Rats infected with T. gondii lose the ability to smell cats, causing them to be eaten for lunch more frequently. One of the ways T. gondii is transmitted, particularly in humans, is through ingestion or inhalation of tiny spores of cat poop. Acute Toxoplasma infections in people can cause delusions and hallucinations, the principal symptoms of schizophrenia. According to the medical literature, one woman infected with T. gondii complained to doctors that she had no veins in her arms or legs. Pregnant women are instructed to avoid cat-litter boxes because T. gondii can cross the placenta and enter the fetus, causing deafness, seizures, mental retardation, cerebral palsy, and changes in head size. It wasn't long before people began referring to T. gondii as Torrey's schizovirus.

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Torrey's assumption is that T. gondii acts like a slow virus. Children who loll about the floor, particularly in crowded urban environments, come into contact with traces of cat feces. The organism invades their brains, staying dormant into late adolescence, when some unexplained biological event allows it to mount a sneak attack. In 1995, Torrey completed a survey of 165 people with serious mental illness, asking how many had had a house cat during childhood. A statistically significant enough number had for him to go live with his theory. Along with his research partner at Johns Hopkins School of Medicine, he published a paper in a very influential journal put out by the National Institute of Mental Health titled "Could Schizophrenia Be a Viral Zoonosis Transmitted from House Cats?" He added this note on the first page: "The authors wish to emphasize that nobody needs to change behavior toward cats on the basis of the following preliminary hypothesis. One of the authors continues to own two cats; the other author continues to allow the neighbor's cat, who believes she owns all houses in the neighborhood, to visit regularly."

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Torrey continued to gather evidence, conducting studies by himself and in conjunction with several infectious-disease specialists who had become quietly interested in the relationship between T. gondii and schizophrenia. They published one study after another showing high levels of Toxoplasma antibodies in the blood of many schizophrenics, which suggested previous T. gondii infection or exposure. Researchers put T. gondii in petri dishes with antipsychotic medications and mood stabilizers to see what would happen. The drugs stopped T. gondii from growing. Torrey had his suspect cornered.

While the psychiatric community has mostly ignored him, the infectious-disease community has been paying Torrey a lot of attention lately, particularly in light of a growing body of research concerning animals and their ability to cause disease. University of Edinburgh researchers recently drew up a list of 1,415 organisms that make humans sick; 61 percent of them are transmitted from animals. Torrey recently published Beasts of the Earth , a book exploring the relationship between animals, humans, and disease?-a hot topic given fears of a bird-flu pandemic that could kill tens of millions of people.....

Though Torrey is getting ready to publish a major survey of all the evidence at hand, he concedes that the distance between his theory and its proof is still wide. There are questions that need to be answered, such as, Why do some people with T. gondii antibodies (Torrey, for example) never develop schizophrenia? One possibility is that some people infected with T. gondii have faulty DNA coding that allows the infection to hang around for many years before the body finally loses its defensive ability. A more damning problem is why people without T. gondii antibodies develop schizophrenia at all. It could be that more than one organism causes the disease. It could be something else that causes the wiring to go bad. "I don't think Toxoplasma will explain 100 percent of schizophrenia cases," Torrey says.