Maybe not your cat, but perhaps the parasites your cat carries. Many cats carry Toxoplasma gondii, and the parasite can easily be transferred to humans. Half of humans are infected with Toxoplasma.

Harmless? No symptoms? Perhaps. Or just maybe not.

But consider what happens to rats infected by Toxoplasma:

Oxford scientists discovered that the minds of the infected rats have been subtly altered. In a series of experiments, they demonstrated that healthy rats will prudently avoid areas that have been doused with cat urine. In fact, when scientists test anti-anxiety drugs on rats, they use a whiff of cat urine to induce neurochemical panic. However, it turns out that Toxoplasma-ridden rats show no such reaction. In fact, some of the infected rats actually seek out the cat urine-marked areas again and again. The parasite alters the mind (and thus the behavior) of the rat for its own benefit.

According to Dr. E. Fuller Torrey of the Stanley Medical Research Institute, and Dr. Robert H. Yolken of the Johns Hopkins University Medical Center, a number of studies link Toxoplasma infection with psychosis:

Recent epidemiologic studies indicate that infectious agents may contribute to some cases of schizophrenia. In animals, infection with Toxoplasma gondii can alter behavior and neurotransmitter function. In humans, acute infection with T. gondii can produce psychotic symptoms similar to those displayed by persons with schizophrenia. Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia. Some medications used to treat schizophrenia inhibit the replication of T. gondii in cell culture. Establishing the role of T. gondii in the etiopathogenesis of schizophrenia might lead to new medications for its prevention and treatment.

cite and link

And Toxoplasma is not alone in being able to alter the minds of its hosts, to the hosts detriment. For examples, look here.

I have wondered over the years why so many people are so enamored of certain politicians who are so bad for them. That was the question raised by, but not satisfactorily explained by What's the Matter with Kansas? Now, I believe, we are getting to the bottom of this mystery. Maybe we all need CAT scans.

More links

For an extended discussion of Toxoplasma by the author of Parasites Rex, link here with interesting information in several comments.

For information on the Toxoplasma gondii Genome Project, link here.

For a study on Toxoplasma gondii and Schizophrenia, link here.

For photos of Toxoplasma, links here, here, and here. Warning: The last link has diagrams of transmission and a photo of an infected baby.

And it that last link is just way too much, how about a SNL skit? link

• SF
• toxoplasmosis