A common parasite in cats can infect humans. The protozoan Toxoplasma gondii feeds on human brain cells, causing altered mental states, behavioral problems and schizophrenia. According to the CDC, up to 60 million people in America suffer from toxoplasmosis, and most don’t know it.
People infected with T. gondii might have no obvious symptoms. If symptoms appear, they may resemble those of the flu. Pregnant women are most at risk. A mother can pass the parasite to her unborn child, causing spontaneous abortion or fetal death.
What is Toxoplasmosis?
Toxoplasmosis is the disease caused by the T. gondii parasite, a protozoan often found in cats. In the larval stage, these one-celled organisms invade the brain and vital organs, eyes, and muscle tissue of the host, where they form tissue cysts.
(above: T. gondii parasites)
In the brain, T. gondii larvae penetrate and consume nerve cells, or neurons, as well as astrocytes. Astrocytes are star-shaped cells with several functions, including message transmission between neurons and non-neuron tissue.
The T. gondii parasite also affects the production of dopamine in the brain. Dopamine, a neurotransmitter, is linked to sexual desire, pleasure and reward.
According to the Centers for Disease Control and Prevention (CDC), toxoplasmosis currently affects up to 60,000,000 people in the United States. Thirty to fifty percent of the world’s population has, or has had, toxoplasmosis. Some estimates put the number at 80%. The high incidence of T. gondii infection occurs because cats are the primary hosts for the parasitic protozoan, and cats and people live closely together. Most infected people are unaware that they have the disease.
Parasitic Mind Control?
Although T. gondii is a microscopic organism, it seems to influence the mind and behavior of its host. By manipulating the reward and pleasure centers of the brain, the parasite can ensure its own survival.
At Oxford University in the UK, Doctors Manuel Berdoy and Joanne Webster conducted a study of the behavior of rats and mice infected with T. gondii cysts. Although rodents normally avoid cats and dislike the smell of cat urine, the study found that rats and mice infected with the parasite showed no fear of cats. When the rodents smelled cat urine, they became sexually aroused. Their testosterone levels rose, and their testes swelled.
The sexual attraction of the rodent to cat urine is in the best interests of the parasite. T. gondii can infect any warm-blooded animal, but can reproduce only inside a cat. If the cat eats the rodent, T. gondii will continue its life cycle.