Let us tell you a horror story.
A single-celled parasite that looks like a tiny spec of orzo pasta infects you. But it doesn’t suck your blood or siphon off some of your food and then be on its way. Instead, it burrows into your muscles and forms cysts that provide a long-term hideout.
Only, that’s not the creepiest thing it does. It also infects your brain and hunkers down in the amygdala, the part of the brain involved in regulating emotions. From that perch, it has the ability to change your behavior in ways that benefit it.
This is the story of Toxoplasma gondii, and the tale above is what happens to rats when infected by it. Studies have shown that rats infected by T. gondii lose their fear of cats, which makes them an easy meal. This is great for hungry cats, but it also works out well for the parasite, which just so happens to reproduce in the digestive tract of cats (without harming them) and is spread through cat poop.
“So there’s a couple of winners,” deadpans University of Colorado professor Christopher Lowry, who recently published a new study illuminating heretofore unknown potential risks from an infection.
“It makes it sound like the pathogen is controlling our minds, but it’s kind of a co-evolutionary relationship.”
Neat?
The potential problem for us is that we can be collateral damage in this transmission cycle. Humans can also be infected by T. gondii and not just through contact with cat poop. Eating unwashed vegetables or undercooked pork or lamb — pigs and sheep can also be infected — can also result in an infection, though it generally doesn’t make you acutely sick or require hospital treatment.
And it turns out that this infection is shockingly common. Lowry, a professor of integrative physiology who studies the link between neural function and emotional behavior, said approximately 10% to 15% of people in the United States show evidence of a previous T. gondii infection. In other countries, it may be much higher — Lowry recently worked on a study looking at people over the age of 65 in Spain and Portugal that found past infection rates of 67%.
So that potentially makes T. gondii a major player in human health. But what does it do to us?
For starters, there’s some evidence that it does impact human behavior and possibly make people less risk-averse. One study concluded that people who had been infected by T. gondii are more likely to cause car accidents. Another says people with an infection are more entrepreneurial. (Lowry cautions that these findings are relative to all sorts of personality factors — it’s not as if everyone with an infection is racing down I-25 like it’s a Formula One course.)
But Lowry and some colleagues wanted to learn about other potential consequences, which brings us back to that study on people from Spain and Portugal. Lowry and his co-authors from CU, the University of Maryland and various universities in Europe looked at measures of frailty in older people and examined whether there was a connection to a T. gondii infection.
They found — deep exhale — that there isn’t. Just looking at what is called seropositivity, which is whether someone has ever been infected, there was no correlation between an infection and frailty later in life.
But they did find an association between frailty and what is called serointensity. In other words, T. gondii may be linked with frailty in people who have been infected a lot.
Lowry said this may have to do with inflammation caused by the parasite, especially certain strains of it.
“The more often you’ve been infected, the more often you may have been exposed to a strain that produces a stronger inflammatory response,” he said.
Overall, Lowry said the takeaway from the study, which was published earlier this month in The Journals of Gerontology, is more of a be-aware kind of message than a be-afraid kind of message.
“From a very big-picture perspective, being infected is not a terrible thing, with one exception,” he said. “If infants acquire the parasite from their mothers, that can have really detrimental effects. So that’s why it’s always advised that pregnant mothers don’t change the kitty litter during pregnancy.”
Even if you are not gestating new life, you can protect yourself by changing the litter box daily and washing your hands well afterward, by avoiding stray cats and the areas they hang out, by thoroughly cooking meat, and by rinsing fruits and vegetables before eating.
English (United States) ·