The cats that were family pets when I was growing up. The cats I have now -- have made me crazy.
OK, maybe I am playing with the hyperbole here. But a Czech scientist, featured in the March issue of The Atlantic, is gaining renown for his theory that a parasite, carried by cats and excreted in their feces, quietly invades human brains and contributes to mental health disorders, such as dementia and schizophrenia, and to car crashes and suicides.
Until recently, evolutionary biologist Jaroslav Flegr, 63, has been toiling in obscurity on taxoplasma (T gondii), the microbe that causes toxoplasmosis, according to The Atlantic article.
Any woman who has been pregnant will remember the admonition against cleaning out cat litter boxes. The reason? Cats -- and their feces -- are the primary source of T. gondii infection in humans. Doctors have long recognized that if a woman becomes infected with the parasite during pregnancy she can transit the disease to her fetus, where it can cause brain damage or death.
I first heard about toxoplasmosis when writing about AIDS in the early 1990s. It was one of those opportunistic infections that afflicts AIDS patients, with their weakened immune systems, and causes dementia in the end stages.
Many people carry the parasite: more than half the people in the world and about 11 percent of the population in the United States, according to positive results in national health screenings. For most children and adults, the infection at most causes mild flu-like systems. Conventional medical thinking says the parasite lies dormant in brain cells. But according to The Atlantic, Flegr and other scientists believes this 'latent'" parasite may be quietly tweaking the connections between our neurons, changing our response to frightening situations, our trust in others and, subtly, our personalities.
My husband read The Atlantic story with great interest. He has schizoaffective disorder -- a mental illness that has features of both schizophrenia and bipolar disorder. As he set the magazine down to tell me about the story, he looked askance at our two cats, Fluffy and Pippin, who were both sleeping at a safe distance from each other on the couch. (Five-month-old Pippin, pictured above, likes to attack 13-year-old Fluffy, hoping she'll play with him; she just hisses, grumbles and swats at him.)
I told my husband he shouldn't blame Fluffy and Pippin. If cat-shedding T. gondii caused his schizophrenia, it's likely he was infected when he was very young. His family had cats when he was growing up.
Flegr himself is T. gondii positive and his passion for the subject stems from his own belief that being infected with the parasite has caused his personality quirks, The Atlantic said.
He blames the protozoan for shrinkage found in the cerebral cortexes of schizophrenia patients. In one study cited in the Atlantic article, almost all schizophrenia patients, shown by MRI scans to have brain shrinkage, tested positive for T. gondii. Another psychiatrist interviewed for the story, reviewed infection data and the MRI scans and concluded: "To me that suggests the parasite may trigger schizophrenia in genetically susceptible people."
Flegr isn't telling people to stopping having cats, The Atlantic says. He has two cats himself. He says indoor cats pose no threat because they would never be exposed to the parasite by hunting and eating rodents and other animals. Even outdoor cats only shed the parasites for three weeks of their lives, "typically when they are young and have just begun hunting."
Pippin will soon start going outside and he will probably want to hunt. During his first few weeks of going outside, we should just be sure to keep the kitchen counters and tables wiped clean.