Toxoplasma gondii, the brain parasite carried by cats, infects sandboxes, gardens, and the soil in play areas.
T. gondii is an extremely interesting parasite that has been at least casually associated with some not-so-great things. A study last year found that people with the parasite have slower reaction times and are more likely to take risks than people without it. Other studies have casually correlated it with suicidal behavior, depression, OCD, and even brain cancer.
T. gondii is bad for you: According to the authors, the idea that T. gondii is "largely asymptomatic" in most of the population is a "notion [that] is now under reconsideration." Concerns include "schizophrenia, depression, suicidal behavior, rheumatoid arthritis, [and] brain cancer."
T. gondii is bad for your child: It's been reported before that toxoplasmosis can result in eye problems and other complications for young children. According to the authors, a new concern is "scholastic underachievement in children," which is bad because...
Cats are everywhere: Between 1989 and 2006, the authors note, the number of pet cats in the United States increased from 54.6 million to 81.7 million. Approximately two thirds of cats sleep with their owners. Remember, most T. gondii infections come from the unwitting ingestion of cat feces.
Which may occur when: a victim is "changing the litter box of a cat, gardening, playing in a sandbox, eating unwashed fruits or vegetables or drinking water containing oocysts."
Is that all? No. They also note that you can get toxoplasmosis from cockroaches and flies that have come into contact with cat feces and then have hung out with your food. Oh, and "T. gondii oocysts may even infect humans who pet dogs that have rolled in cat feces."
Toxoplasma oocysts are unkillable
"Because cats do not defecate randomly but rather select places with loose soil so that they can cover their feces gardens, children’s play areas with loose soil, and especially sandboxes (also called sandpits and sand piles) are favored sites."
And your kids eat sand: In another, mostly humorous study done at a Massachusetts daycare center, kids "ingested a median of 40 mg of soil per day." Except for one bright kid who "consumed 5-8 grams of soil per day on average." Even without the whole eating sand thing, "oocysts are known to become aerosolized when they dry out,it is also possible that a child playing in such a sandbox could become infected simply by breathing in oocysts."
... a study done in Japan that calculated the number of T. gondii oocysts in three separate sandboxes. One of them had 1.7 million per square foot; it takes just one to infect a human.