The image of an eccentric elderly woman with a house full of cats is a familiar one. It turns out cats—particularly cat litter, and what’s in it—are associated with a parasitic infection that may affect your behavior, and lead to that eccentricity. The parasite, Toxoplasma gondii, can lead to much more dire consequences than a certain reputation in the neighborhood.
The T. gondii parasite is actually quite common. Most infections in the U.S. are from cat waste. Litter boxes are an obvious culprit, but feral cats that visit backyard gardens can leave the parasite there, meaning you can get it from your landscaping even if you don’t think you have cats. In fact, feral cats—which hunt—are more likely to carry T. gondii than domestic cats who live on packaged food. If you’re working in the garden, try not to touch your face, and wash your hands after. If you have neither cats nor a garden, you can be infected by raw or undercooked meat, particularly lamb, pork, or venison, or by unwashed fruits or vegetables. Knives and surfaces that come into contact with raw meat can spread T. gondii as well if not thoroughly washed.
As many as one-third of all Americans are estimated to carry T. gondii, but in most cases it has no symptoms, particularly in adults with healthy immune systems. Sometimes, infected people develop flu-like symptoms such as achiness, swollen lymph nodes, fever, and fatigue. In people with weak or compromised immune systems, T. gondii infection can be more serious. HIV-positive people, people undergoing chemotherapy, and organ transplant patients who have or have had a T. gondii infection as well sometimes suffer seizures or blurred vision. Babies born to women who get toxoplasmosis while pregnant—particularly during the third trimester—are frequently stillborn, and those who survive are prone to seizures, jaundice, and other health problems. Often these health problems don’t appear for quite a few years.
Another effect of T. gondii is a greater likelihood of developing schizophrenia, and a tendency to risk-taking behaviors. A recent study in Sweden found a possible explanation for this linkage. The researchers found that T. gondii stimulated the production in the brain of a substance called GABA, which suppresses fear and anxiety. The effect has been observed in humans and rats; it is speculated that it helps spread the disease by making rats less afraid of cats, the parasite’s preferred host.